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Lower-Body Torque and Power Declines Across Six Decades in Three Hundred Fifty-Seven Men and Women: A Cross-sectional Study With Normative Values

Leyva, Arturo1; Balachandran, Anoop1; Signorile, Joseph F.1,2

Journal of Strength and Conditioning Research: January 2016 - Volume 30 - Issue 1 - p 141–158
doi: 10.1519/JSC.0000000000001083
Original Research
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Leyva, A, Balachandran, A, and Signorile, JF. Lower-body torque and power declines across six decades in three hundred fifty-seven men and women: a cross-sectional study with normative values. J Strength Cond Res 30(1): 141–158, 2016—This study presents age-specific and gender-specific patterns and normative values for lower-body isokinetic performance in 195 women and 162 men, 18–80 years of age, using data collected from 1991 to 2004. Peak torque (PT) and average power (AP) during knee extension (KE), knee flexion (KF), ankle plantar flexion, and dorsiflexion (DF) at 1.05, 3.14, and 5.24 rad·s−1 were compared by decade. Knee extension and KF at all speeds showed a significant main effect by age group (G). Men's KEPT and KEAP at 60 and 70 G were significantly different than 20, 30, and 40 G at all speeds. Additionally, 50 G differed from all other groups. For women, 50, 60, and 70 G KEPT and KEAP at 5.24 rad·s−1 differed significantly from all other age groups. Men's KFPT and KFAP showed no differences among 20, 30, and 40 G, whereas 50 G differed from all groups except 60 G. For KFPT and KFAP, women 20 and 30 G differed from other age groups at all testing speeds. Plantar flexion and DF performance declines were speed specific mainly occurring at 3.14 rad·s−1. The results reflect declines in strength and power beginning during the fifth decade in men, and earlier in women. The study also provides normative values, which may be used to evaluate neuromuscular performances by gender across decades of life.

1Laboratory of Neuromuscular Research and Active Aging, Department of Kinesiology and Sports Sciences, University of Miami, Coral Gables, Florida; and

2Center on Aging, Miller School of Medicine, University of Miami, Miami, Florida

Address correspondence to Joseph F. Signorile, jsignorile@miami.edu.

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Introduction

Exponential declines of 20–40% in force, speed, and power have been reported by the seventh and eighth decades of life (17,32). These declines in neuromuscular performance (termed dynapenia) are commonly associated with reduced fiber number, atrophy, fewer type II fibers, and loss of motor neurons (42,44).

Although exercise is commonly used as an intervention to ameliorate dynapenia, most controlled studies have delayed this intervention until the seventh decade of life. This customary delay seems based on the definition of the term elderly (50,78), rather than performance assessments. This is problematic because patterns of neuromuscular decline with age differ among individuals due to factors such as smoking, diet, debilitating disease, socioeconomic status, education levels, marital status, and perceived health (16,69). Additionally, patterns of decline differ by gender, although exercise has been shown to benefit both men and women (69). Given these differences, and the lack of linearity between losses in muscle mass and function, a performance-based assessment of age-related declines is more appropriate than a simple assessment of muscle mass or lean body tissue when diagnosing individuals' exercise requirements (35,45).

Concerning neuromuscular performance variables, power has been reported to have a greater association with functional capacity than strength (5,7,53,56,63,71); however, the latter cannot be discounted as an important factor affecting mortality, disability, frailty, and fall probability (6,22,46,57). Additionally, gait speed is associated with power at a specific position along the force-velocity curve (12), and the velocity at which maximal knee extensor (KE) power occurs is correlated to chair rise, stair climb, and walking performances in older women (9). Therefore, speed-specific declines in neuromuscular performance are an important consideration when assessing individuals' specific needs.

In terms of the biomechanical specificity, although elbow extension power (31) and grip strength (15,36) are associated with independence, KE and plantar flexor (PF) power have been repeatedly linked to critical activities, including rising from a chair, stair climbing, and walking (5,7,12,31,53,63,71). Additionally, we have shown that KE and PF isokinetic peak torque (PT) and average power (AP) at 1.05, 3.14, and 5.20 rad·s−1 correlated with ramp power and gallon jug testing (65,66), whereas Whipple et al. (77) reported a significant relationship between fall probability and isokinetic strength and power of the KE, knee flexors (KF), PF, and dorsiflexors (DF) at 1.05 and 2.09 rad·s−1.

Given the varying patterns of decline across age (63) and the fact that most studies have compared young (20–30 years) and old people (60 years and above) and have not taken into account middle-aged individuals (40–60 years) (13,39,79), developing normative values from early adulthood through old age using a proven neuromuscular evaluation, like isokinetics, would be an important tool for assessing functional declines and developing targeted prevention strategies at the appropriate time and level for each individual. Therefore, this study examined the differences in isokinetic PT and AP during KE, KF, PF, and DF across 6 decades in men and women.

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Methods

Experimental Approach to the Problem

To assess the effect of age and gender on knee (flexion and extension) and ankle (dorsiflexion and PF) isokinetic PT and AP at different speeds across 6 decades, a cross-sectional design was employed using data collected across multiple studies and clinical assessment over more than a decade. These variables were chosen due to their recognized relationships to independence, fall probability, and mortality across the aging process.

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Subjects

Participants were recruited predominantly from the Miami-Dade County, Florida. The final revised database contained 357 adults, aged 19–80 years. To be included, subjects had to be living independently and have no severe musculoskeletal impairment or unstable chronic disease states, and a Mini-Mental State Examination score above 18. All subjects signed approved informed consent forms approved by the University of Miami's Subcommittee for the use and Protection of Human Subjects before testing. Subject characteristics and sample sizes are presented in Tables 1 and 2, respectively.

Table 1

Table 1

Table 2

Table 2

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Procedures

Figure 1 presents a study CONSORT chart. Data files were reviewed and compiled into one electronic file by the study coordinator. After initial transcription, 3 additional researchers repeated the compilation process generating a second electronic file. The 2 files were then compared and errors were corrected by further examination of the original data. To minimize instrument and calibration errors, all data were collected using the same Biodex System 2 Dynamometer (Biodex Medical Systems, Shirley, NY, USA). Also, the dynamometer was calibrated at the start of each testing week according to the Biodex System 2 manual. The laboratory's testing protocol was consistent across all testing sessions because all researchers were trained and evaluated by one of the authors (J.F.S.). The reliability of this devise has been confirmed for these exercises (52,75). During each test, dynamometer settings were adjusted to provide optimal mechanical advantage for each participant. All analyses were performed using data collected from participants' right legs. Each participant was familiarized with the testing protocol and given 3 practice trials at 3.14 rad·s−1 before testing. During acclimatization, participants were told to move at 50, 75, and 100% of their maximum perceived movement speed and to attend to changes in resistance felt at each speed. This procedure was used to teach participants the concept of isokinetic testing, specifically, the necessity to meet the dynamometer speed settings so that resistance would be generated. Tests were then performed at 1.05, 3.14, and 5.24 rad·s−1 with the order being randomized. Before each test, the participant performed 3 warm-up repetitions at 50, 75, and 100% of perceived effort and was then provided a short recovery. Testers provided consistent verbal encouragement during testing. They also performed visual assessments of performance curves to ensure participants performed maximally. A minimum of 2 minutes recovery was provided between testing speeds. No attempt was made to control for the time of the day of the testing. There was no set time frame. Each joint was evaluated during separate days, and the testing order was randomized. All data were windowed to reduce the impact of acceleration and deceleration artifacts.

Figure 1

Figure 1

The AP and PT for the KE, KF, PF, and DF were included for 3 testing speeds, 1.05, 3.14, and 5.24 rad·s−1, and compared by decade and gender. The age groups were 20–29 (20 G), 30–39 (30 G), 40–49 (40 G), 50–59 (50 G), 60–69 (60 G), and 70 years and older (70 G).

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Statistical Analyses

Descriptive statistics were performed for all dependent variables to describe each age group's physical characteristics and isokinetic strength capabilities. A series of one-way ANOVAs with age group as the independent variable and isokinetic leg extension, leg curl, ankle dorsiflexion, and PF strength at 3 different speeds as the dependent variables were conducted. Fisher's least significant difference post hoc tests were used to detect differences among age groups. All significance tests were 2-tailed, and an alpha level of 0.05 was required for significance. Precision of the outcomes was reported using 95% confidence intervals (CI). All statistical tests were performed using the SPSS, version 21 statistical package (IBM SPSS Statistics, Armonk, NY, USA).

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Results

Knee Extension (Men)

The mean values and SE for men's KEPT and KEAP by age group at 1.05, 3.14, and 5.24 rad·s−1 are presented in Table 3. Figure 2 illustrates patterns across age groups for KEPT (Figure 2A) and KEAP (Figure 2B). Men's KE results at all speeds demonstrated a significant main effect by age group. Post hoc analyses showed that 40 G KEPT and KEAP values were significantly higher than 50, 60, and 70 G at all speeds, demonstrating a decline by participants' fifth decade. At 1.05 rad·s−1, the largest KEPT declines were seen between 40 and 50 G (Mdiff = 45.8 ± 14.6; p < 0.005). There were also significant differences between 40 and 60 G (Mdiff = 62.9 ± 10.3 N·m, p < 0.005), and 40 and 70 G (Mdiff = 89.9 ± 10.9 N·m, p < 0.005).

Table 3

Table 3

Figure 2

Figure 2

For KEAP, patterns were similar. At 1.05 rad·s−1, significant differences existed between 40 and 50 G (Mdiff = 67.4 ± 21.9 W, p < 0.005), 60 G (Mdiff = 96.6 ± 15.6 W, p < 0.005), and 70 G (Mdiff = 133.9 ± 16.3 W, p < 0.005). At 3.14 rad·s−1, significant differences were seen between 40 and 50 G (Mdiff = 67.4 ± 21.9 W, p < 0.005), 60 G (Mdiff = 96.6 ± 15.6 W, p < 0.005), and 70 G (Mdiff = 133.9 ± 16.3 W, p < 0.005). At 5.24 rad·s−1, significant differences existed between 40 and 50 G (Mdiff = 15.0 ± 6.5 W, p < 0.005), 60 G (Mdiff = 29.4 ± 4.6 W, p < 0.005), and 70 G (Mdiff = 37.6 ± 4.8 W, p < 0.005).

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Knee Extension (Women)

Women's KE results are presented in Table 4. Figure 2 illustrates patterns across age groups for KEPT (Figure 2C) and KEAP (Figure 2D). For KEPT at all speeds, 50 G was significantly different than groups, except 40 G at 3.14 rad·s−1. For KEPT and KEAP, 60 G was significantly different from all groups except KEAP at 5.24 rad·s−1. For 20, 30, and 40 G, the 40 G showed significantly lower KEPT than 20 G at 5.24 rad·s−1 (Mdiff = 11.9 ± 5.4 N·m, p < 0.005).

Table 4

Table 4

Women's KEAP at 5.24 rad·s−1 showed significant differences between 40 and 50 G (Mdiff = 47.7 ± 14.3 W, p < 0.005), 60 G (Mdiff = 45.7 ± 12.2 W, p < 0.005), and 70 G (Mdiff = 65.1 ± 12.3 W, p < 0.005). The decline at 3.14 rad·s−1 showed an identical pattern; however, the decline at 1.05 rad·s−1 was more gradual.

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Knee Flexion (Men)

Men's KFPT and KFAP results are presented in Table 5 and Figure 3. No differences were seen in KFPT between 20, 30, and 40 G, whereas 50 G differed from all groups except 60 G. The greatest differences in 50 G for PT were at 1.05 rad·s−1 (40 G: Mdiff = 22.0 ± 8.4 N·m, p < 0.005; 30 G: Mdiff = 19.4 ± 9.5 N·m, p < 0.005; 20 G: Mdiff = 27.1 ± 9.1 N·m, p < 0.005). The men's knee KFAP showed similar patterns across all testing speeds with 50 G significantly different from all younger groups and 70 G at the 2 lower testing speeds.

Table 5

Table 5

Figure 3

Figure 3

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Knee Flexion (Women)

Table 6 and Figure 3 present women's KFPT and KFAP results, which show a more linear decline than men across age groups. For 50, 60, and 70 G, KFPT differed significantly from 20 to 40 G, and from each other. Interestingly, 20 and 30 G differed significantly in KFPT at 1.05 rad·s−1 (Mdiff = 13.2 ± 6.0 N·m, p < 0.005), 3.14 rad·s−1 (Mdiff = 9.8 ± 4.5 N·m, p < 0.005), and 5.24 rad·s−1 (Mdiff = 11.4 ± 4.3 N·m, p < 0.005); and for AP at 1.05 rad·s−1 (Mdiff = 10.9 ± 5.0 W, p < 0.005), 3.14 rad·s−1 (Mdiff = 22.8 ± 9.4 W, p < 0.005), and 5.24 rad·s−1 (22.6 ± 10.5 W, p < 0.005). Post hoc comparisons also showed significant mean differences between the 20 and 30 G at 1.05 rad·s−1 (p < 0.005), 3.14 rad·s−1 (p < 0.005), and 5.24 rad·s−1 (p < 0.005).

Table 6

Table 6

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Ankle Plantar Flexion (Men)

Results for men's PFPT and PFAP are shown in Table 7 and Figure 4. Significant differences among age groups were detected for both variables (p ≤ 0.05) with a curvilinear pattern of decline except for PFAP at 5.24 rad·s−1. For men's PFPT at 1.05 rad·s−1, 20 G was significantly different from 70 G (Mdiff = 25.15 ± 9.55 N·m, p < 0.005). At 3.14 rad·s−1, 40 G differed from 70 G. At 5.24 rad·s−1, no differences were detected.

Table 7

Table 7

Figure 4

Figure 4

For PFAP, 60 G was significantly lower than 40 G (Mdiff = 28.5 ± 10.0 W, p < 0.005), 30 G (Mdiff = −31.9 ± 11.3 W, p < 0.005), and 20 G (Mdiff = 29.32 ± 11.31 W, p < 0.005) at 3.14 rad·s−1. At 1.05 rad·s−1, 50 G differed from 40 G (Mdiff = 12.6 ± 5.3 W, p < 0.005).

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Ankle Plantar Flexion (Women)

The patterns of change for PFPT and PFAP were again more linear for women than men (Table 8 and Figure 4). For PFPT at 1.05 rad·s−1, 50 G differed from 40 G (Mdiff = 18.6 ± 8.0 N·m, p < 0.005). At 3.14 rad·s−1, PFPT for 70 G was significantly lower than 40 G (Mdiff = 16.9 ± 7.3 N·m, p < 0.005), 30 G (Mdiff = 16.03 ± 6.9 N·m, p < 0.005), and 20 G (Mdiff = 27.6 ± 6.9 N·m, p < 0.005). At 5.24 rad·s−1, 40 G was lower than 20 G (Mdiff = 17.9 ± 7.9 N·m, p < 0.005).

Table 8

Table 8

At 1.05 rad·s−1, PFAP for 50 G was lower than 40 G (Mdiff = 12.5 ± 4.0 W, p < 0.005), 30 G (Mdiff = 10.4 ± 4.6 W, p < 0.005), and 20 G (Mdiff = 18.3 ± 4.4 W, p < 0.005). At 3.14 rad·s−1, 50, 60, and 70 G were significantly different from 40 G. At 5.24 rad·s−1, 40 G was 40.1% lower than 20 G (Mdiff = 20.9 ± 10.3 W, p < 0.005).

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Ankle Dorsiflexion (Men)

Dorsiflexion peak torque and DFAP results are presented in Table 9 and Figure 5. Both variables showed significant group effects (p ≤ 0.05) confined to 1.05 rad·s−1. For DFPT, the only differences were between 70 and 40 G (Mdiff = 7.8 ± 3.1 N·m, p < 0.005). For DFAP at 1.05 rad·s−1, significant differences were seen between 40 and 50 G (Mdiff = 4.5 ± 1.9 W, p < 0.005), 60 G (Mdiff = 4.0 ± 1.8 W, p < 0.005), and 70 G (Mdiff = 6.9 ± 2.0 W, p < 0.005).

Table 9

Table 9

Figure 5

Figure 5

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Ankle Dorsiflexion (for Women)

Dorsiflexion peak torque performance also showed a main effect by age group with a more curvilinear pattern than for men (Table 10 and Figure 5). At 1.05 rad·s−1, DFPT for 70 G was different from 40 G (Mdiff = 7.3 ± 2.9 N·m, p < 0.005), 30 G (Mdiff = 6.9 ± 2.8 N·m, p < 0.005), and 20 G (Mdiff = 8.5 ± 2.8 N·m, p < 0.005). Dorsiflexion average power also showed significant differences at 1.05 rad·s−1 between 50 and 20 G (Mdiff = 3.5 ± 1.4 W, p < 0.005).

Analyses comparing our results with those of Runnels et al. (60) for KEPT and KFPT at 1.05 and 3.14 rad·s−2 in 75 men across the same age groups show the strong parallels between the two studies (Figures 6–9, Table 11). Figure 10 provides a sample graph of the mean values and 95% CI across age groups for men's leg extension torque at 3.14 rad·s−1.

Table 10

Table 10

Figure 6

Figure 6

Figure 7

Figure 7

Figure 8

Figure 8

Figure 9

Figure 9

Table 11

Table 11

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Discussion

The principal findings of this study were that men and women showed different patterns of decline in isokinetic strength and power across the 6 decades included in these analyses, and that the patterns of change varied by movements and speed. As noted above, statistically significant declines in men's KEPT and KEAP at all speeds occurred between 50 and 59 years of age; however, these declines began insidiously decades earlier. Knee flexion results followed the same pattern with declines earlier than expected, especially at 5.24 rad·s−1. Our data closely match those of Runnels et al. (60) for KEPT and KFPT across the same age groups at 1.05 and 3.14 rad·s−1 in 75 men. Figures 6–9 present age cross-sectional plots (a), scatter plots with best fit lines and 95% CI (b), and Bland-Altman plots (c) comparing our results with theirs for KEPT at 1.05 and 3.14 rad·s−1, and KFPT at the same speeds. Additionally, Table 11 provides intraclass correlations, Bland-Altman statistics, and Chronbach's Alpha scores for each comparison.

Our findings also reflect those from a longitudinal study by Frontera et al. (23) for KE and KF in 9 men aged 65.4 ± 4.2 years. These researchers reported a decline of 38 ± 24 N (−23.7 ± 14.6%) in KEPT at 1.05 rad·s−1 compared with the 46.1 N·m (32.7%) decline seen in our study at the same testing speed. Our results are slightly outside the 95% CI (16.2–31.2%) in their study. Knee flexion peak torque patterns were also comparable with a reduction of 30 ± 29 N (28.5 ± 23.3%) in their study compared with a 26.4 N·m (35.9%) decline in our study with our results falling within the 95% CI for their study (CI = 19.0–38.0%). A second study by the same research team reported a decline of 22.4 ± 8.9% (98.5 ± 27.4 to 76.3 ± 23.4 N·m) for KEPT and 5.9 ± 19.4% (56.7 ± 16.9 to 59.5 ± 18.9 N·m) for KFPT at 1.05 rad·s−1 over 8 years (24). The 21.3% decline in KEPT in our study fell within the 95% CI for KEPT (16.6–28.2%), whereas the 17.8% decline in KFPT was slightly higher than the upper CI (−2.7 to 14.5%) for KFPT in their study. However, the increase in KFPT seen by Frontera et al. (23) is not consistent with the other studies we have reviewed.

Another study reported declines between 10 and 22% in KEPT at speeds between 0.52 and 5.15 rad·s−1 in 73- to 83-year-old men over 7 years (3). These researchers then identified additional declines of 25–35% in KE performance at 0.52 rad·s−1, 11 years later (29). Our observed declines for these age groups across the 3 testing speeds averaged 28–47% for 7 and 11 years, respectively, somewhat higher than these researchers, respectively. As Raj et al. (54) note in their review, testing speeds and activity levels may affect the isokinetic test results. This may explain, in part, the somewhat greater declines seen as in our study, especially in the 9 subjects in the 11-year follow-up by Grimby (29) in which most subjects reported unchanged levels of physical activity. Additionally, our results are from a much larger sample and are cross sectional rather than longitudinal.

Women's KE shows a very different pattern than men's. Although PT at 1.05 rad·s−1 exhibited a curvilinear pattern similar to men, declines at higher testing speeds were nearly linear. Knee extension average power exhibited linear declines across age groups at all speeds with far greater slopes at 3.14 and 5.24 rad·s−1. Women's KFPT and KFAP also showed a linear, albeit less drastic, declines. Our findings reflect those reported previously in older women. Greeves et al. (28) reported values ranging from 116.5 ± 8.4 to 131.0 ± 8.7 N·m at 1.05 rad·s−1 during repeated measures of their sample of postmenopausal women (50.05 ± 3.84 years) across their 39 week testing period. These results compare favorably with our 40 and 50 G women who produced PT of 125.7 ± 8.1 and 104.4 ± 5.2 N·m, respectively.

Although, to the best of our knowledge, no studies have looked at these variables in men and women across 6 decades, our findings are in line with other studies using isokinetic and other contractile testing conditions in both genders. For example, Hortobágyi et al. (34) tested 18 to 80-year-old men and 20 to 74-year-old women using isometric and isokinetic concentric and eccentric KE contractions at 1.05, 2.09, and 3.14 rad·s−1. Although direct comparisons are not possible given the differences in measurement units and dynamometers (Biodex vs. Kin-Com), these researchers reported approximately a 7 and 8% decline in KE torque production per decade for men and women, respectively, which compares favorably with the 7.4% in men and 7.6% in women by decade declines in this study. Unfortunately, the linear regression modeling in their study makes comparisons of patterns of decline impossible. In 2 separate studies, Goodpaster et al. (25,26) reported average values of 132.3 ± 34.5 and 81.4 ± 22.0 N·m for white and black men and women 73.7 ± 2.9 and 73.4 ± 2.8 years of age, which compare favorably with the values of 127.4 ± 4.8 and 73.3 ± 2.1 N·m for the men and women in our study. Declines across 3 years reported by these researchers for white and black men (15.4 ± 21.4, 19.7 ± 26.4 N·m) and white and black women (8.0 ± 22.5, 10.2 ± 19.8 N·m) compare favorably with the 7.4 and 7.6% declines by decade for men and women in our study. A longitudinal study by Hughes et al. (35) examining changes in isokinetic strength in 68 women and 52 men, 46–78 years of age, reported 11.8 ± 15.5 and 14.5 ± 15.6% declines in KEPT for women and men, respectively, across 9.7 ± 1.1 years. These declines are comparable with the 16.9, 18.9, and 13.4% declines in women and 21.1, 9.9, and 17.5% declines in men seen when across decades for 40, 50, and 60 G in this study. Additionally, our data show the same patterns of decline for KEPT of men and women 19–80 as reported in the Baltimore Longitudinal Study of Aging in 786 individuals aged 26–96 (48), similar KEPT values to those reported in the Health ABC study for men and women 72–83 years (70), and similar patterns for KEPT and KFPT in the MOST cohort study (61) incorporating 3,856 men and women aged 61.6 ± 8.1 and 62.2 ± 7.7, respectively.

To summarize, we believe this study is the first to show the patterns of decline for KE and KF for men and women across 6 decades and to demonstrate that declines begin during the fourth and fifth decade for women and men, respectively. This suggests that preventative exercise programming should begin earlier in a person's life span than previously suggested.

Men's PF declines differed from patterns for knee joint tests beginning later, exhibiting a more curvilinear pattern, and affecting AP more than PT. Additionally, there were no significant differences among age groups for PFPT or PFAP at 5.24 rad·s−1. The differences between KF and KE results and PF results may be attributable to a number of factors. First, PF incorporates a second class lever designed for force rather than velocity. This limits individuals' capacities to attain the necessary movement speeds to meet isokinetic testing demands at higher testing speeds. Second, the compliance of the Achilles tendon slows the rate of force development for the triceps surae compared with other muscles with similar fiber type distributions (2). Finally, our tests were performed at a 2.36 rad knee angle favoring the contribution of the slower soleus muscle over the faster gastrocnemius (64,72).

Although PFPT and PFAP studies are limited, our PFPT values for men are consistent with those of other studies. Our PFPT values (20 G = 76.68 ± 7.32 N·m, 30 G = 78.51 ± 8.18 N·m) are similar to preintervention values of 17 healthy men (aged 26–41 years) who participated in a 90-day bed rest study (1). Cunningham et al. (11) examined PFPT on a Cybex II (Lumex Inc., New York, USA) dynamometer in 25 older sedentary (n = 6; 64.0 ± 3.0 years), older active (n = 7, 63.0 ± 3.0 years), younger sedentary (n = 6, 20.8 ± 1.9 years), and younger active (n = 6, 22.5 ± 1.8 years) men. Peak torque at 1.05 rad·s−1 was approximately 36, 43, 49, and 64 N·m for older sedentary and active, and younger sedentary and active groups, respectively. At 3.14 rad·s−1, these values were approximately 8, 12, 18, and 21 N·m for the same groups, respectively. These values are considerably below the 59.03 ± 4.99 and 43.62 ± 4.98 N·m seen at 1.05 and 3.14 rad·s−1 for our 60 G, and the 76.68 ± 7.32 and 52.60 ± 7.65 N·m seen at these speeds for our 20 G. A number of factors may have produced the differences between these results and those reported in our study and the study by Alkner and Tesch (1). First, differences in dynamometers may have affected the results. We used a Biodex System 2, Alkner and Tesch (1) used a Cybex 6000, and Cunningham et al. (11) used a Cybex II. Second, the testing protocols varied considerably. Our subjects were seated in the Biodex accessory chair (angles: seatback = 0.26 rad, footplate = 0.79 rad, knee = 2.16 rad, hiprad) and performed 3 repetitions at 3 speeds alternating PF and DF. Additionally, speed specific warm-ups were performed at 50, 75, and 100% of perceived effort. Subjects in the Alkner and Tesch (1) study performed concentric and eccentric movements at 0.52 and 1.05 rad·s−1 while supine with hips semi-flexed at a 1.57 rad knee angle. These researchers provided no indications of a warm-up. Finally, Cunningham et al. (11) tested their subjects prone with the knee in full extension using 5 repetitions at 5 speeds ranging from 0.52 to 3.14 rad·s−1. Unfortunately, no information was provided concerning the method of returning the foot to the original position after each contraction. Third, data selection and analyses methods differed. Fourth, verbal encouragement was provided by the testers in our study and the study Alkner and Tesch; it is unclear whether verbal encouragement was provided by Cunningham et al. (11). Finally, differences existed in data sampling and analysis. We recorded 3 repetitions at each speed with the highest being used for analysis. Data in our study were windowed to reduce acceleration and deceleration artifacts, especially at 5.24 rad·s−1. Alkner and Tesch (1) used the higher of 2 contractions for analyses, and no indications of filtering were provided. Cunningham et al. (11) collected undamped signals on an analog oscilloscope and used an average of the 5 repetitions at each speed.

Women's ankle PF results again indicate that declines begin to decline earlier for women than men. Peak torque and AP in men were maintained (except for 5.24 rad·s−1) until 50 G, whereas women showed a nearly linear decline in these variables across age groups. Clearly, women's results show a greater number of differences across age groups and more overlaps among groups.

Women's PFPT results compare favorably results of some studies, but differ considerably from others. Plantar flexor peak torque values in a training study by Klentrou et al. (40) using weighted vests with women 44–62 years old (1.05 rad·s−1: controls, 47.3 ± 19.5 N·m and exercisers, 37.8 ± 8.4 N·m; 3.14 rad·s−1: controls, 30.9 ± 8.3 N·m and exercisers, 27.9 ± 7.0 N·m) are comparable with those of our 50 G group at these testing speeds. A training study by Eyigor et al. (20) examined the impact of a group exercise program on functional factors, including isokinetic strength, in 20 women aged 70.3 ± 6.5 years. They reported isokinetic pretest and posttest scores for subjects' dominant legs at 1.05 rad·s−1 of 20.40 ± 5.90 and 25.30 ± 8.05 N·m, respectively, and 9.95 ± 3.15 and 12.40 ± 3.17 N·m at 3.14 rad·s−1, which were somewhat lower than the 36.8 ± 3.4 and 23.4 ± 3.3 N·m values for our 70 G women at these testing speeds. In contrast, in a reliability study by Webber and Porter (75) involving 30 women (73.3 ± 4.7 years), PF strengths at 0.52 and 1.57 rad·s−1 averaged 66.7 ± 20.0 and 69.7 ± 20.2 N·m for day 1 and day 2, respectively, at 0.52 rad·s−1; and 61.4 ± 15.8 and 62.0 ± 18.5 N·m for day 1 and day 2, respectively, at 1.57 rad·s−1. These values are notably higher that the 36.8 ± 3.4 N·m average for the 70 G in our study. Again, differences may have been due to the dynamometers used (Biodex System 2, Cybex 2, and Biodex System 3), body positioning, passive return vs. alternating DF and PF movements, and variations in the testing protocols. Additionally, Webber and Porter (75) reported peak rather than AP values.

Studies incorporating men and women reported results similar to ours for PF. In a reliability study by Hartmann et al. (30) combining men and women (W: n = 18, age = 69.9 ± 5.0 years; M: n = 6, age = 75.0 ± 5.6 years), peak PF torques were 41.0 ± 15.8 and 42.6 ± 15.5 N·m for days 1 and 2, respectively. At the same testing speed, our 70 G produced 50.5 ± 4.4 N·m for men and 36.8 ± 3.4 N·m for women. In a second study by Trappe et al. (74), employing 14 men and 4 women, 23–51 years, isokinetic PTs at 1.05, 3.14, and 5.24 rad·s−1 were 88.5, 41.7, and 16.8 N·m, respectively. The lower speed values compare favorably with the 68.3 ± 9.6 to 82.4 ± 5.0 N·m and 50.7 ± 8.0 to 58.0 ± 5.2 N·m for the 20 G through 50 G in our study, but are considerably lower than the 44.4 ± 14.0 to 49.6 ± 10.8 N·m seen for this age range at 5.24 rad·s−1. Additionally, Buchner et al. (8) reported an average PFPT of 40 ± 22 N·m for men and women 60–96, which again mirrors our results for our 60 and 70 G men and women.

Plantar flexion results could have been affected by subjects' training histories. Krishnathasan and Vandervoort (41) reported that PF values at 0.52, 1.57, and 3.14 rad·s−1 varied 35–46% between endurance-trained vs. resistance-trained middle-aged individuals.

In terms of men's DFPT and DFAP at 3.14 and 5.24 rad·s−1, the declines were so small and gradual that no significant differences could be detected across age groups. However, at 1.05 rad·s−1, there was a significant difference for AP in the means of the 40 and 50 G suggesting that a 30% decline in this variable begins during middle age.

For studies involving men exclusively, our results are comparable with those of earlier studies. Our DFPT and DFAP results differed somewhat from those of Ranisavljev et al. (55) who examined the relationship between strength and power of the hip, knee, and ankle joints in relation to gait transition speed. For their DFPT and DF power values at 1.05 rad·s−1, using reported body weights and isokinetic values per unit body weight, we computed values of 39.26 ± 8.64 N·m and 25.91 ± 5.50 W; and at 3.14 rad·s−1, values were 33.76 ± 8.64 N·m and 31.40 ± 13.35 W. These values fell slightly outside the 95% CI for our PT values at each speed, whereas their power values were within the 95% CI for AP in our 20 G. The most obvious difference between the studies is the compressed age range (20–24 years) in their study compared with ours (20–29 years). The second factor was that our study used the Biodex 2 dynamometer, whereas they used a KinCom. And finally, the differences in the protocols for the Biodex and KinCom may have been a significant source of variance.

In a study of the isokinetic ankle function of 48 young male athletes and 25 nonathletic young men, So et al. (68) reported DFPT between 28.7 ± 6.6 and 31.3 ± 6.3 N·m at 1.05 rad·s−1 and DFPT at 3.14 rad·s−1 between 13.3 ± 3.5 and 17.3 ± 3.9 N·m. Their data are nearly identical to our results at 1.05 rad·s−1 (28.24 ± 2.59 N·m), but lower than our results at 3.14 rad·s−1, although still falling within the 95% CI at this speed. The difference between our data and theirs at 3.14 rad·s−1 should be considered in light of the aforementioned data reported by Ranisavljev et al. (55).

Women's results showed a loss of one third of DFAP at the lower speed of 1.05 rad·s−1 between 50 and 20 G. In contrast to women's PF results, DF values in our study compared favorably with nearly every other study. Webber and Porter (75) reported torque values of 14.0 ± 4.6 and 13.9 ± 4.8 N·m for day 1 and day 2 at 0.52 rad·s−1 and 10.5 ± 4.2 and 10.6 ± 4.1 N·m for day 1 and day 2 at 1.57 rad·s−1. These values compare favorably with the average value of 13.19 ± 1.34 N·m produced by our 70 G group. As would be expected, their peak power values (day 1: 7.2 ± 2.3 W, day 2: 7.1 ± 2.5 W at 0.52 rad·s−1; day1: 11.2 ± 4.5 W, day 2: 10.9 ± 4.4 W at 1.57 rad·s−1) were somewhat higher than the average value of 6.43 ± 0.90 reported for our 70 G. Our DFPT data also reflected those of Eyigor et al. (20) in women, 70.3 ± 6.5 years of age. Dorsiflexion peak torque at 1.05 and 3.14 rad·s−1 ranged from 3.8 ± 2.07 to 7.15 ± 2.75 N·m and 3.35 ± 2.18 to 6.10 ± 2.97 N·m, respectively, across their trained and untrained conditions. These results were slightly below those of our 70 G group at 1.05 rad·s−1 but fell near the midpoint of the 95% CI for this group at 3.14 rad·s−1.

Compared with studies involving both men and women, our results are also defensible. In a study, examining ankle DFPT in older men (78.2 ± 4.9 years) and women (74.7 ± 3.8 years) subjected to a 2-week isokinetic training program, Connelly and Vandervoort (10) illustrated DFPT at 3.14 rad·s−1 of approximately 15 N·m for pretest and posttest. As would be expected, this average value which included men and women fell between the 19.42 ± 6.37 N·m for men and 5.66 ± 0.80 N·m for women at 70 G. Our DFPT findings agree with those of Thomas et al. (73) for the control group in their study examining lower extremity strength after anterior cruciate ligament injury and reconstruction. Seven men and 8 women (24.73 ± 3.37 years) were tested on a Biodex System 3 dynamometer at 1.05 rad·s−1. Average DFPT was 20.09 ± 8.18 N·m, which compares well with the values of 28.24 ± 2.59 and 21.72 ± 1.81 N·m recorded for the 20 G men and women in our study, respectively. In a reliability study by Holmbäck et al. (33), DFPT at 1.05 rad·s−1 for men and women was 35.0 ± 7.5 and 28.8 ± 4.8 N·m, which was slightly above the 95% CI for each gender in our 20 G group. Our average results for men and women in the 60 and 70 G (19.12 ± 2.73 N·m) compared favorably with those of Buchner et al. (8) for men and women 60–90 years of age (15 ± 7 N·m), with the lower average attributable to the older upper age limit in their study. Our results differ from those reported by Hartman et al. (30), where DFPT values at 1.05 rad·s−1 were 10.4 ± 4.7 and 10.2 ± 4.2 N·m for days 1 and 2 compared with our values of 17.0 ± 2.0 N·m (60 G) and 13.2 ± 1.3 (70 G) for women and 25.8 ± 1.2 (60 G) and 20.5 ± 1.7 N·m (70 G) for men. The differences between their results and those reported by us and others are difficult to explain.

Among the strengths of this study were the inclusion of reciprocal KE, KF, PF, and DF data across 6 decades of life; the separation of results by age group and gender, the large sample size which allowed us to generate normative values, and the inclusion of knee and ankle test results allowing comparisons of varying patterns of change in PT and AP across decades for each joint movement. Limitations include the limited samples in some gender/age blocks, the inability to match these results with longitudinal results for activities of daily living performance, fall probability or other more practical measures of independence and injury risk, and the lack of specific information on activity levels, diet, and effort during testing, inherent to studies incorporating maximal testing.

Future studies should compare them with existing data from isokinetic studies examining such topics as sarcopenia (51), muscle quality (14), obesity and osteoporosis (37), fall risk, and fall-related injuries (58,62). Additionally, further correlation studies should be performed comparing results from the Biodex System 2, 3, and 4 and other dynamometers, so our results can be applied to all dynamometers and our database can be expanded. Furthermore, an examination of comparative results employing different testing procedures is warranted to allow greater standardization.

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Practical Applications

Strength and power declines have been previously observed in aging individuals. To the best of our knowledge, this study is the first to show age-specific and gender-specific lower-body strength and power patterns in a large sample (357 men and women) across 6 decades. In line with our research goal to provide practical diagnostic tools, our results provide gender-specific normative values across more than 6 decades of life. Using our results to assess neuromuscular declines during the aging process vs. more standardize strength measurements, such as handgrip strength, is supported by the recent study by Felicio et al. (21) indicating the poor correlations between isokinetic KEs and flexor performance and handgrip strength, and cautioning against using handgrip strength as an indicator of global muscle strength in older community dwelling women. A number of studies have concluded that exercise and other forms of physical activity are the most viable interventions for maintaining muscle mass, function, and quality of life (4,19,38,43,47,67,76), and reducing fall probability (18,27,49,59) in the elderly. However, our results show compelling evidence that prevention strategies should be implemented substantially earlier in life because declines begin in selected muscle groups as early as the fourth and third decades of life in men and women, respectively; and that declines may be more drastic during middle age than previously proposed. The use of our normative scores will allow a more exacting diagnostic assessment of older individuals' needs and provide a much needed assessment tool for lower-body strength and power. We also suggest that the curves and results provided allow a simple assessment of chronological vs. functional age. We have also provided a sample graph of the mean values and 95% CI across age groups for men's leg extension torque at 3.14 rad·s−1 (Figure 10). Both methods can be used as an effective tool to evaluate if subjects are declining at a faster or slower rate than expected.

Figure 10

Figure 10

This is of special importance in this population where lower-body neuromuscular performance is so important for reducing falls and maintaining independence.

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Acknowledgments

There was no external funding associated with this study, the authors have no professional relationships with any company or manufacturer who could benefit from the results of this study and have no conflicts of interest to report. The results of this study do not constitute endorsement of any product by the authors or the NSCA. The authors thank all the students who over the past decade helped with the collection of these data and the subjects who graciously gave their time and effort.

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References

1. Alkner BA, Tesch PA, Mid-Sweden University, Faculty for Human Sciences and Department of Health. Knee extensor and plantar flexor muscle size and function following 90 days of bed rest with or without resistance exercise. Eur J Appl Physiol 93: 294–305, 2004.
2. Alway SE, MacDougall JD, Sale DG. Contractile adaptations in the human triceps surae after isometric exercise. J Appl Physiol (1985) 66: 2725–2732, 1989.
3. Aniansson A, Hedberg M, Henning GB, Grimby G. Muscle morphology, enzymatic activity, and muscle strength in elderly men: A follow-up study. Muscle Nerve 9: 585–591, 1986.
4. Balachandran A, Krawczyk SN, Potiaumpai M, Signorile JF. High-speed circuit training vs hypertrophy training to improve physical function in sarcopenic obese adults: A randomized controlled trial. Exp Gerontol 60: 64–71, 2014.
5. Bassey EJ, Fiatarone MA, O'Neill EF, Kelly M, Evans WJ, Lipsitz LA. Leg extensor power and functional performance in very old men and women. Clin Sci 82: 321–327, 1992.
6. Batista F, Gomes G, Neri A, Guariento M, Cintra F, de Sousa M, D'Elboux M. Relationship between lower-limb muscle strength and frailty among elderly people. Sao Paulo Med J 130: 102–108, 2012.
7. Bean JF, Kiely DK, Herman S, Leveille SG, Mizer K, Frontera WR, Fielding RA. The relationship between leg power and physical performance in mobility-limited older people. J Am Geriatr Soc 50: 461–467, 2002.
8. Buchner DM, Larson EB, Wagner EH, Koepsell TD, de Lateur BJ. Evidence for a non-linear relationship between leg strength and gait speed. Age Ageing 25: 386–391, 1996.
9. Clémençon M, Hautier CA, Rahmani A, Cornu C, Bonnefoy M. Potential role of optimal velocity as a qualitative factor of physical functional performance in women aged 72 to 96 Years. Arch Phys Med Rehabil 89: 1594–1599, 2008.
10. Connelly DM, Vandervoort AA. Effects of isokinetic strength training on concentric and eccentric torque development in the ankle dorsiflexors of older adults. J Gerontol A Biol Sci Med Sci 55: B465–B472, 2000.
11. Cunningham DA, Morrison D, Rice CL, Cooke C. Ageing and isokinetic plantar flexion. Eur J Appl Physiol Occup Physiol 56: 24–29, 1987.
12. Cuoco A, Callahan DM, Sayers S, Frontera WR, Bean J, Fielding RA. Impact of muscle power and force on gait speed in disabled older men and women. J Gerontol A Biol Sci Med Sci 59: 1200–1206, 2004.
13. Dalton BH, Power GA, Vandervoort AA, Rice CL. Power loss is greater in old men than young men during fast plantar flexion contractions. J Appl Physiol (1985) 109: 1441–1447, 2010.
14. Delmonico MJ, Harris TB, Visser M, Park SW, Conroy MB, Velasquez-Mieyer P, Boudreau R, Manini TM, Nevitt M, Newman AB, Goodpaster BH; Health, Aging, and Body. Longitudinal study of muscle strength, quality, and adipose tissue infiltration. Am J Clin Nutr 90: 1579–1585, 2009.
15. den Ouden ME, Schuurmans MJ, Arts IEMA, van der Schouw YT. Association between physical performance characteristics and independence in activities of daily living in middle-aged and elderly men. Geriatr Gerontol Int 13: 274–280, 2013.
16. Donini LM, Savina C, Cannella C. Eating habits and appetite control in the elderly: The anorexia of aging. Int Psychogeriatr 15: 73–87, 2003.
17. Edwén CE, Thorlund JB, Magnusson SP, Slinde F, Svantesson U, Hulthén L, Aagaard P; Institute of Medicine, Department of Internal Medicine and Clinical Nutrition, Institute of Neuroscience and Physiology, Department of Clinical Neuroscience and Rehabilitation, Sahlgrenska Academy, University of Gothenburg, Sahlgrenska akademin. Stretch-shortening cycle muscle power in women and men aged 18–81 years: Influence of age and gender. Scand J Med Sci Sports 24: 717–726, 2014.
18. El-Khoury F, Cassou B, Charles M, Dargent-Molina P. The effect of fall prevention exercise programmes on fall induced injuries in community dwelling older adults: Systematic review and meta-analysis of randomised controlled trials. BMJ 347: 1–13, 2013.
19. Evans AK, Durham MP, Sandler D, Van Bemden A, Stanzino D, Signorile JF. Correlation between isokinetic tests and functional tests of the frail elderly population. Med Sci Sports Exerc 34: S56, 2002.
20. Eyigor S, Karapolat H, Durmaz B. Effects of a group-based exercise program on the physical performance, muscle strength and quality of life in older women. Arch Gerontol Geriatr 45: 259–271, 2007.
21. Felicio D, Pereira L, Pereira D, Assumpcao A, de Jesus-Moraleida F, de Queiroz B, da Silva J, Rosa N, Dias J, Thomasini R. Poor correlation between handgrip strength and isokinetic performance of knee flexor and extensor muscles in community-dwelling elderly women. Acta Physiol 211: 183, 2014.
22. Finlayson ML, Peterson EW. Falls, aging, and disability. Phys Med Rehabil Clin N Am 21: 357–373, 2010.
23. Frontera WR, Hughes VA, Fielding RA, Fiatarone MA, Evans WJ, Roubenoff R. Aging of skeletal muscle: A 12-yr longitudinal study. J Appl Physiol (1985) 88: 1321–1326, 2000.
24. Frontera WR, Reid KF, Phillips EM, Krivickas LS, Hughes VA, Roubenoff R, Fielding RA. Muscle fiber size and function in elderly humans: A longitudinal study. J Appl Physiol (1985) 105: 637–642, 2008.
25. Goodpaster BH, Carlson CL, Visser M, Kelley DE, Scherzinger A, Harris TB, Stamm E, Newman AB. Attenuation of skeletal muscle and strength in the elderly: The Health ABC Study. J Appl Physiol (1985) 90: 2157–2165, 2001.
26. Goodpaster BH, Park SW, Harris TB, Kritchevsky SB, Nevitt M, Schwartz AV, Simonsick EM, Tylavsky FA, Visser M, Newman AB. Health ABC Study. The loss of skeletal muscle strength, mass, and quality in older adults: The health, aging and body composition study. J Gerontol A Biol Sci Med Sci 61: 1059–1064, 2006.
27. Grabiner MD, Crenshaw JR, Hurt CP, Rosenblatt NJ, Troy KL. Exercise-based fall prevention: Can you be a bit more specific? Exerc Sport Sci Rev 42: 161–168, 2014.
28. Greeves JP, Cable NT, Reilly T, Kingsland C. Changes in muscle strength in women following the menopause: A longitudinal assessment of the efficacy of hormone replacement therapy. Clin Sci 97: 79–84, 1999.
29. Grimby G. Muscle performance and structure in the elderly as studied cross-sectionally and longitudinally. J Gerontol A Biol Sci Med Sci 50: 17–22, 1995.
30. Hartmann A, Knols R, Murer K, de Bruin ED. Reproducibility of an isokinetic strength-testing protocol of the knee and ankle in older adults. Gerontology 55: 259–268, 2009.
31. Herman S, Kiely DK, Leveille S, O'Neill E, Cyberey S, Bean JF. Upper and lower limb muscle power relationships in mobility-limited older adults. J Gerontol A Biol Sci Med Sci 60: 476–480, 2005.
32. Himann JE, Cunningham DA, Rechnitzer PA, Paterson DH. Age-related changes in speed of walking. Med Sci Sports Exerc 20: 161–166, 1988.
33. Holmbäck AM, Porter MM, Downham D, Lexell J. Reliability of isokinetic ankle dorsiflexor strength measurements in healthy young men and women. Scand J Rehabil Med 31: 229–239, 1999.
34. Hortobágyi T, Zheng D, Weidner M, Lambert NJ, Westbrook S, Houmard JA. The influence of aging on muscle strength and muscle fiber characteristics with special reference to eccentric strength. J Gerontol A Biol Sci Med Sci 50: B399–B406, 1995.
35. Hughes VA, Frontera WR, Wood M, Evans WJ, Dallal GE, Roubenoff R, Fiatarone Singh MA. Longitudinal muscle strength changes in older adults: Influence of muscle mass, physical activity, and health. J Gerontol A Biol Sci Med Sci 56: B209–B217, 2001.
36. Incel NA, Sezgin M, As I, Cimen OB, Sahin G. The geriatric hand: Correlation of hand-muscle function and activity restriction in elderly. Int J Rehabil Res 32: 213–218, 2009.
37. Kim TN, Baik SH, Choi DS, Choi KM, Yang SJ, Yoo HJ, Lim KI, Kang HJ, Song W, Seo JA, Kim SG, Kim NH. Prevalence of sarcopenia and sarcopenic obesity in Korean adults: The Korean sarcopenic obesity study. Int J Obes 33: 885–892, 2009.
38. King AC. Interventions to promote physical activity by older adults. J Gerontol A Biol Sci Med Sci 56: 36–46, 2001.
39. Klein CS, Allman BL, Marsh GD, Rice CL. Muscle size, strength, and bone geometry in the upper limbs of young and old men. J Gerontol A Biol Sci Med Sci 57: M455–M459, 2002.
40. Klentrou P, Slack J, Roy B, Ladouceur M. Effects of exercise training with weighted vests on bone turnover and isokinetic strength in postmenopausal women. J Aging Phys Act 15: 287–299, 2007.
41. Krishnathasan D, Vandervoort AA. Ankle plantar flexion strength in resistance and endurance trained middle-aged adults. Can J Appl Physiol 27: 479–490, 2002.
42. Larsson L, Li X, Frontera WR. Effects of aging on shortening velocity and myosin isoform composition in single human skeletal muscle cells. Am J Physiol 272: C638–C649, 1997.
43. LaStayo PC, Ewy GA, Pierotti DD, Johns RK, Lindstedt S. The positive effects of negative work: Increased muscle strength and decreased fall risk in a frail elderly population. J Gerontol A Biol Sci Med Sci 58: M419–M424, 2003.
44. Lexell J, Taylor CC, Sjöström M. What is the cause of the ageing atrophy? Total number, size and proportion of different fiber types studied in whole vastus lateralis muscle from 15- to 83-year-old men. J Neurol Sci 84: 275–294, 1988.
45. Manini TM, Clark BC. Dynapenia and aging: An update. J Gerontol A Biol Sci Med Sci 67A: 28–40, 2012.
46. Metter EJ, Talbot LA, Schrager M, Conwit R. Skeletal muscle strength as a predictor of all-cause mortality in healthy men. J Gerontol A Biol Sci Med Sci 57: B359–B365, 2002.
47. Miszko TA, Cress ME, Slade JM, Covey CJ, Agrawal SK, Doerr CE. Effect of strength and power training on physical function in community-dwelling older adults. J Gerontol A Biol Sci Med Sci 58: 171–175, 2003.
48. Moore AZ, Caturegli G, Metter EJ, Makrogiannis S, Resnick SM, Harris TB, Ferrucci L. Difference in muscle quality over the adult life span and biological correlates in the Baltimore Longitudinal Study of Aging. J Am Geriatr Soc 62: 230–236, 2014.
49. Ni M, Mooney K, Richards L, Balachandran A, Sun M, Harriell K, Potiaumpai M, Signorile JF. Comparative impacts of Tai Chi, balance training, and a specially-designed yoga program on balance in older fallers. Arch Phys Med Rehabil 95: 1620–1628.e30, 2014.
50. Orimo H, Ito H, Suzuki T, Araki A, Hosoi T, Sawabe M. Reviewing the definition of “elderly”. Geriatr Gerontol Intern 6: 149–158, 2006.
51. Pahor M, Manini T, Cesari M. Sarcopenia: Clinical evaluation, biological markers and other evaluation tools. J Nutr Health Aging 13: 724–728, 2009.
52. Porter MM, Holmbäck AM, Lexell J. Reliability of concentric ankle dorsiflexion fatigue testing. Can J Appl Physiol 27: 116–127, 2002.
53. Puthoff ML, Nielsen DH. Relationships among impairments in lower-extremity strength and power, functional limitations, and disability in older adults. Phys Ther 87: 1334–1347, 2007.
54. Raj IS, Bird SR, Shield AJ. Aging and the force-velocity relationship of muscles. Exp Gerontol 45: 81–90, 2010.
55. Ranisavljev I, Ilic V, Markovic S, Soldatovic I, Stefanovic D, Jaric S. The relationship between hip, knee and ankle muscle mechanical characteristics and gait transition speed. Hum Mov Sci 38: 47–57, 2014.
56. Rantanen T, Avela J. Leg extension power and walking speed in very old people living independently. J Gerontol A Biol Sci Med Sci 52: M225–M231, 1997.
57. Rantanen T, Guralnik JM, Sakari-Rantala R, Leveille S, Simonsick EM, Ling S, Fried LP. Disability, physical activity, and muscle strength in older women: The women's health and aging study. Arch Phys Med Rehabil 80: 130–135, 1999.
58. Rao SS. Prevention of falls in older patients. Am Fam Physician 72: 81–88, 2005.
59. Rose DJ, Hernandez D. The role of exercise in fall prevention for older adults. Clin Geriatr Med 26: 607–631, 2010.
60. Runnels ED, Bemben DA, Anderson MA, Bemben MG. Influence of age on isometric, isotonic, and isokinetic force production characteristics in men. J Geriatr Phys Ther 28: 74–84, 2005.
61. Segal NA, Glass NA, Torner J, Yang M, Felson DT, Sharma L, Nevitt M, Lewis CE. Quadriceps weakness predicts risk for knee joint space narrowing in women in the MOST cohort. Osteoarthritis Cartilage 18: 769–775, 2010.
62. Serra Rexach JA. Clinical consequences of sarcopenia [in Spanish]. Nutr Hosp 21(Suppl 3): 46–50, 2006.
63. Signorile JF. Bending the Aging Curve: The Complete Exercise Guide for Older Adults. Champaign, IL: Human Kinetics, 2011.
64. Signorile JF, Carmel MP, Czaja SJ, Asfour SS, Morgan RO, Khalil TM, Ma F, Roos BA. Differential increases in average isokinetic power by specific muscle groups of older women due to variations in training and testing. J Gerontol A Biol Sci Med Sci 57: M683–M690, 2002.
65. Signorile JF, Sandler D, Kempner L, Stanziano D, Ma F, Roos BA. The ramp power test: A power assessment during a functional task for older individuals. J Gerontol A Biol Sci Med Sci 62: 1266–1273, 2007.
66. Signorile JF, Sandler D, Ma F, Bamel S, Stanziano D, Smith W, Sandals L, Roos BA. The gallon-jug shelf-transfer test: An instrument to evaluate deteriorating function in older adults. J Aging Phys Act 15: 56–74, 2007.
67. Slade JM, Miszko TA, Laity JH, Agrawal SK, Cress ME. Anaerobic power and physical function in strength-trained and non-strength-trained older adults. J Gerontol A Biol Sci Med Sci 57: M168–M172, 2002.
68. So CH, Siu TO, Chan KM, Chin MK, Li CT. Isokinetic profile of dorsiflexors and plantar flexors of the ankle—A comparative study of élite versus untrained subjects. Br J Sports Med 28: 25–30, 1994.
69. Strawbridge WJ, Camacho TC, Cohen RD, Kaplan GA. Gender differences in factors associated with change in physical functioning in old age: A 6-year longitudinal study. Gerontologist 33: 603–609, 1993.
70. Strotmeyer ES, de Rekeneire N, Schwartz AV, Resnick HE, Goodpaster BH, Faulkner KA, Shorr RI, Vinik AI, Harris TB, Newman AB; Health ABC Study. Sensory and motor peripheral nerve function and lower-extremity quadriceps strength: The health, aging and body composition study. J Am Geriatr Soc 57: 2004–2010, 2009.
71. Suzuki T, Bean JF, Fielding RA. Muscle power of the ankle flexors predicts functional performance in community-dwelling older women. J Am Geriatr Soc 49: 1161–1167, 2001.
72. Tamaki H, Kitada K, Akamine T, Sakou T, Kurata H. Electromyogram patterns during plantarflexions at various angular velocities and knee angles in human triceps surae muscles. Eur J Appl Physiol Occup Physiol 75: 1–6, 1997.
73. Thomas AC, Villwock M, Wojtys EM, Palmieri-Smith RM. Lower extremity muscle strength after anterior cruciate ligament injury and reconstruction. J Athl Train 48: 610–620, 2013.
74. Trappe SW, Trappe TA, Lee GA, Costill DL. Calf muscle strength in humans. Int J Sports Med 22: 186–191, 2001.
75. Webber SC, Porter MM. Reliability of ankle isometric, isotonic, and isokinetic strength and power testing in older women. Phys Ther 90: 1165–1175, 2010.
76. Westerterp KR, Meijer EP. Physical activity and parameters of aging: A physiological perspective. J Gerontol A Biol Sci Med Sci 56: 7–12, 2001.
77. Whipple RH, Wolfson LI, Amerman PM. The relationship of knee and ankle weakness to falls in nursing home residents: An isokinetic study. J Am Geriatr Soc 35: 13–20, 1987.
78. World Health Organization. Definition of an Older or Elderly Person. Health Statistics and Health Information Systems. 2012. Available at: http://www.who.int/healthinfo/survey/ageingdefnolder/en/index.html. Accessed December 10, 2014.
79. Young A, Stokes M, Crowe M. Size and strength of the quadriceps muscles of old and young women. Eur J Clin Invest 14: 282–287, 1984.
Keywords:

isokinetic; elderly; aging; strength

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