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An Isokinetic Training Program for Reducing Falls in a Community-Dwelling Older Adult: A Case Report

Beebe, Justin A. PT, PhD1; Hines, Roger W. PT, DPT, OCS1,2; McDaniel, Laura T. PT, DPT, OCS1,2; Shelden, Brenda L. PT, DPT, ATC1,3

Journal of Geriatric Physical Therapy: July/September 2013 - Volume 36 - Issue 3 - p 146–153
doi: 10.1519/JPT.0b013e31826e73d5
Case Report

Background: With the population older than 65 years, projected to double by the year 2030, falls in older adults are a substantial health concern. Muscle strength deficits are one of the multifactorial components linked to increased fall risk, and decreasing these deficits has been one of the goals of interventions designed to decrease fall risk. These interventions have traditionally focused on improving peak torque; however, recent research suggests that exercise protocols that focus on the rate of torque development (RTD) may be more effective in decreasing fall risk.

Purpose: This case report examines clinical outcomes following implementation of an isokinetic strengthening protocol coupled with a balance program designed to reduce fall risk in a community-dwelling older adult.

Methods: The individual was a 70-year-old woman with a history of 3 falls over the past 8 months and no related medical etiology who had self-limited her activities because of fear of another fall. She was classified as having substantial risk for future falls because of fall history, increased fear of falling, and below age norms on the Berg Balance Scale (BBS), and the Timed Up and Go (TUG). The treatment program consisted of 12 weeks of high-intensity isokinetic knee extensor training, high challenge dynamic gait and balance activities, and core strengthening. The isokinetic protocol consisted of 4 sets of 10 concentric-only repetitions at speeds of 240°/sec and 300°/sec for a total of 8 work sets. Dynamic gait activities incorporating directional and obstacle drills, and rocker and balance boards were used for balance training activities. Progressive theraband exercises were used for core strengthening. As her home program, the participant was encouraged to return to line dancing twice per week. During the 12-week protocol, the participant completed two 90-minute therapy sessions and two 90-minute dance classes per week.

Results: After the 12 weeks of treatment, knee extensor peak torque at 150 ms improved on the right from 67.8 N to 107.1 N (57.9% increase), and on the left from 65.1 N to 97.6 N (49.9% increase). The BBS score improved from 45 to 52; and the TUG improved from 14.0 to 8.6 seconds. Both final scores exceeded fall risk cutoffs (BBS = 48; TUG = 13.5 seconds) and the change score exceeded minimal detectable change (BBS = 7; TUG 5.4 seconds).

Conclusions: The treatment program produced improvements in knee extensor peak torque and RTD, but more importantly, the final scores on the clinical outcome measures placed the participant above established fall-risk cutoff scores. Although future research with increased numbers of participants and a control group should be conducted to confirm this study's results, these findings support the use of isokinetic training to reduce fall risk in older adults.

1Department of Physical Therapy, University of South Dakota, Vermillion.

2Center for Industrial and Physical Therapy, New Bern, North Carolina.

3Mat-Su Regional Medical Center, Palmer, Alaska.

Address correspondence to: Justin A. Beebe, PT, PhD, Department of Physical Therapy, University of South Dakota, 414 E. Clark St, Vermillion, SD 57069 (

This study was approved by the University of South Dakota Human Research Protection Office (Project 2011.180). It was internally funded and there are no declared conflicts of interest for any author.

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Falls in older adults have become a substantial public health concern. It has been estimated that, in a given year, 1 in 3 adults aged 65 or older will fall,1 and a previous history of falls is one of the major risk factors for falling multiple times.2 Falls result in 90% of all hip fractures in older adults; with 1 in 4 previously community-dwelling older adults requiring a nursing home stay at least a year to return to prefracture levels of independence.3 Even in the absence of serious injury, a fall often initiates a downward cascade where fear of another fall leads to limited activity, resulting in functional impairments and increased fall risk.4

The costs associated with falls present a significant burden for the health system and the individual. Nationwide, yearly direct care costs as a result of falls have been estimated as high as $200 million for fatal falls, and $19 billion for nonfatal falls.5 These statistics take on even greater importance as the portion of the population older than 65 years is estimated to double by the year 2030.6

Physical therapists provide evaluation, fall risk reduction, and prevention interventions for individuals at risk for falls. Interventions often consist of some combination of strengthening, balance, and gait drills but are not prescribed with a standardized approach to program design or the exercise dosage, duration, or intensity required to produce successful outcomes. Recent research has identified specific program components, which include program dosage, duration, and exercise intensities associated with structured exercise interventions that decrease fall risk.7–10 In addition, other research has indicated that resistive exercise protocols that focus on improving the rate of torque development (RTD) rather than peak torque are more effective in preventing falls.11–14

Isokinetic based strengthening exercises appear to be ideally suited to the higher intensity exercises required to improve RTD in older adults. A benefit of using an isokinetic dynamometer is that it does not allow the limb to accelerate beyond a preset angular velocity, thus maximal acceleration of an exercise load is possible without the danger of exceeding safe movement speeds due to the influence of momentum.15 Angular joint velocities of 325°/s to 380°/s have been reported during self-selected gait by healthy controls 64 to 75 years of age, and the range of angular velocities allowed by an isokinetic dynamometer is well suited to safely match these speeds.16 Also, unlike isotonic exercise where the load is limited by the strength at the weakest point in the range, isokinetic exercise allows for maximum loading throughout the range of motion.15 Research has also shown that isokinetic exercise at 240°/s and 300°/s maximized quadriceps muscle activation per unit of work, and that this mode of exercise can be particularly useful in emphasizing neural adaptations, motor unit recruitment, and firing rate and most closely approximates the maximal recruitment found with high isotonic loads without subjecting individuals to unnecessarily heavy training loads.17 A previous study utilizing isokinetic exercise to produce improvements in RTD in a population of older female participants with history of falls did not find significant improvement; however, that protocol utilized slower angular joint velocities, lower exercise work load, and protocol duration of 8 weeks.18

The purpose of this case report is to describe clinical outcomes following a structured exercise intervention, which utilized a new protocol for isokinetic strengthening, RTD; and which incorporated an evidence-based program design, dosage, duration, and intensities to reduce fall risk in a community-dwelling older adult. This study was approved by the University's Office of Human Subjects Protection.

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Participant History

The participant was a well-nourished 70-year-old white woman who lived alone at home. She was referred to physical therapy for evaluation because of complaints of unstable gait after a history of 3 falls over the last 8 months. A retired homemaker, she enjoyed water-painting, volunteering at a local library, and line dancing several times a week for exercise, but had reduced her volunteer activities and eliminated her dancing due to fear of another fall. She was a nonsmoker, rarely drank alcoholic beverages, and did not utilize an assistive device. All of her falls had occurred while ambulating indoors, once while stepping backwards and twice after losing her balance while walking in the home. The participant denied any consumption of alcoholic beverages concurrent with any of the falls. She sustained no serious injuries in her falls and had resisted previous attempts for referral to physical therapy.

The participant's relevant medical history included cardiac-related pathology, depression, gastrointestinal and genitourinary conditions, and age-related vision changes for which she had utilized bifocals for the past 5 years. The participant had recently undergone a cardiac workup and was cleared for participation in the treatment plan. The medications the participant was taking at the time of the initial evaluation are listed in Table 1. Though interactions between esomeprazole (Nexium) and diazepam can increase the risk of central nervous system depression, and metoprolol Succinate (Toprol) and bupropion (Wellbutrin) can interact to increase the risk of hypotension, she had no changes in her medication regimen in the previous 18 months and her physician did not feel her medications contributed to her falls.

Table 1

Table 1

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The participant's height was 160 cm, and she weighed 61.2 kg; thus, her body mass index was 23.9. At initial evaluation, her blood pressure was 116/68 mm Hg, heart rate was 68 beats per minute, and respiration rate was 16 breaths per minute while seated and 112/61 mm Hg, 73 beats per minute, and 16 breaths per minute, respectively, while standing. Active and passive range of motion were within normal limits and pain free for the trunk and all 4 extremities. Gross manual muscle testing per Kendall et al19 was used to assess the strength of the hip flexors, abductors, extensors, and the ankle dorsiflexors with a grade of 4/5 obtained throughout. Plantarflexion was tested with repeated standing heel raises20 with a grade of normal. Knee extensor strength was tested isometrically on a LIDO isokinetic dynamometer (Loredan Biomedical Incorporated, West Sacramento, California) with the participant seated and the knee joint angle set at 60° of flexion. Knee extensor strength was the focus of the isokinetic testing due to its close correlation to functional status, performance measures, and gait speeds in older adults.21–23 No deficits were noted in the lower extremities for light touch sensation,24 coordination,25 or proprioception.26

Two clinical outcome measures were used to objectively quantify the participant's functional abilities before and after the physical therapy intervention: the Berg Balance Scale (BBS) and the Timed Up and Go (TUG). The BBS, which has established reliability27–30 and validity,27–30 was selected because the included items test postural control and balance, and the results can be used to predict fall risk in older adults. The BBS utilizes 14 tasks, which are scored on a 0 to 4 scale with a maximum score of 56 and a cutoff score of 48, below which it identifies those at risk for falls (84% sensitivity, 78% specificity).29 The reported minimal detectable change (MDC), or the amount of improvement required to distinguish true change from measurement error, for the BBS is 5.31 Upon initial evaluation, the participant scored a 45/56 and demonstrated difficulty with 6 items: (1) safely stand unsupported with her eyes closed for 10 seconds; (2) stand with her feet together for 1 minute; (3) reach forward 25 cm while standing; (4) pick an object from the ground; (5) stand with one foot in front of the other for 30 seconds; or (6) stand on 1 leg for greater than 10 seconds. Complete details of BBS scoring can be found in Table 2.

Table 2

Table 2

The TUG was selected for testing mobility and is valid and reliable for use with community-dwelling older adults.32–35 The TUG is a timed test which requires a subject to stand up, walk 3 meters, turn around, walk back and sit down. The cutoff score for being considered a participant a faller is taking 13.5 seconds or longer to complete the test (87% sensitivity, 87% specificity).33 The reported MDC for the TUG is 4 seconds.36 Upon initial evaluation, the participant's TUG time was 14.0 seconds.

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Clinical Impression

On the basis of the Guide to Physical Therapist Practice,37 the participant was classified in Practice Pattern 5A: Primary Prevention/Risk Reduction for Loss of Balance and Falling, and based upon examination findings was given a diagnosis of abnormality of gait due to decreased postural stability, decreased lower quarter strength, and impaired balance reactions. Recent meta-analyses,7,8 a systematic review,9 and a Cochrane review10 suggest that multifactorial programs that incorporate strengthening, dynamic gait drills, and functional balance training elements are effective in decreasing fall risk for community-dwelling older adults. This participant was a candidate for physical therapy intervention and she agreed to participate in a multifactorial program, which included the above elements to address her strength deficits and attempt to reduce her risk of falling.

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As with the initial strength testing, the strengthening protocol developed for this participant focused on improving knee extensor strength due to its close correlation to functional status, performance measures, and gait speed in older adults21–23 but utilized a new protocol for isokinetic strengthening. Although improved maximal strength or peak torque has traditionally been the focus of such protocols, the time required to generate peak torque, or RTD, in the quadriceps muscles, even in a young, athletic population, can be greater than 350 ms.38 The timeframe to initiate a compensatory step to prevent a fall can be as short as 250 ms.39–41 Newly emerging evidence has identified the RTD as having greater impact on fall prevention than peak torque11–14 as RTD determines the degree of acceleration during the initial phase of a movement, and therefore, also influences movement velocity.42–44 Research suggests that older adults utilize a compensatory step as their preferred method of recovery in response to a balance disturbance.39–41 Therefore, a high RTD would enable the individual to adequately react within the limited time frame and range of motion of a compensatory step and produce a robust response to a loss of balance.39–41 Alternatively, a low RTD, even in the presence of a high peak torque, may negate the ability to utilize that peak torque in response to the loss of balance.42

To measure change in RTD, a baseline was established during the second treatment where the participant performed four 3-second maximal isometric repetitions with three 1-minute rest intervals. The data generated were displayed on a time versus torque graph and RTD was determined by the torque reading 150 ms after the point of departure from the zero torque baseline. The 150-ms window was chosen because during gait, quadriceps activation begins late in the swing phase and rapidly increases to a peak during the loading response requiring rapid generation of force within 150 ms.45 The repetition producing the highest peak torque was utilized for the measurement of RTD. Final RTD testing was performed in the same manner as the initial measures.

Following the initial evaluation, the participant completed a 12-week program consisting of a 10-minute warm up on a NuStep T5XR (NuStep Inc, Ann Arbor, Michigan) seated stepper followed by the isokinetic strengthening protocol. The protocol consisted of 4 sets of 10 concentric only repetitions at speeds of 240°/s and 300°/s for a total of 8 work sets, each separated by 3-minutes rest. During the first 4 treatments, only 2 sets at each speed were performed to allow for accommodation to the exercise load. The physical therapy program also included dynamic gait drills, functional balance training, and core strengthening (Table 3). Dynamic gait drills included activities such as marching, sidestepping, change of direction on command, obstacle courses, and dual task gait. As the participant progressed, these tasks were progressed in difficulty by intensifying the challenge to balance, and increasing the number of tasks per treatment session. Functional balance training utilized rocker and balance boards for static balance and weight shifting drills. Balance training was progressed by reducing upper extremity support (2 hands to 1 hand to no hands), narrowing the base of support, and incorporating dual task drills. Core strengthening was performed using theraband resistance. Table 3 presents a sample treatment session, including time, and rules for progression. The duration and mix of activities was purposefully varied at each treatment session to minimize practice effect and maximize the participant's ability to respond to unexpected balance challenges. Obtaining the minimum effective dose of 50 hours of exercise required to produce improvements in fall risk7 would be difficult utilizing solely clinic based exercise, but because this individual had previously enjoyed line dancing she was encouraged to return to this activity. Line dancing involves specific steps, exaggerated weight shifts, and changes of direction in time with music and in close quarters with other dancers. The participant returned to line dancing twice per week, considering it her home exercise program.

Table 3

Table 3

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Following the isokinetic strengthening protocol, both peak torque and RTD had marked increases. Peak torque improved by 28.5% and 37.4% (right and left, respectively), and RTD improved by 57.9% and 49.9% (right and left, respectively; Figure 1). The results of both clinical outcome measures are summarized in Table 4. The participant's BBS score increased by 7 points, above the MDC of 5,31 and one which placed her above the fall-risk cutoff score.29 The BBS item which demonstrated the greatest improvement was her ability to pick up a shoe from the floor that she was unable to do during baseline testing. The following BBS items also demonstrated improvement: standing unsupported with eyes closed for 10 seconds, standing unsupported with feet together for 1 minute, and reaching forward 25 cm while standing. Scores for the BBS items of standing unsupported with 1 foot in front of the other for 30 seconds, and single leg stance for greater than 10 seconds had improved but were still difficult (Table 2). The participant's TUG time decreased by 5.4 seconds, a change also above the MDC of 4 seconds,33 and one which placed her below the fall-risk cutoff score.36 Pre- and postintervention item scores for the BBS and pre- and postintervention TUG times are presented in Table 4.

Figure 1

Figure 1

Table 4

Table 4

Subjectively, the participant reported improvements in walking, balance, and confidence with daily activities with no falls reported during the course of the intervention. She reported an increase in line dancing participation and that she no longer “sat out” faster or more involved/challenging dances but viewed them as a challenge. In terms of motivation to continue exercise, she reported she realized the importance of exercise and no longer viewed it as “something that worked for other people.”

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The purpose of this study was to document the effect of a 12-week, structured exercise program on clinical outcome measures in an older female participant with history of falls. While the exercise program included dynamic gait drills and high challenge functional balance activities, the primary intervention of interest was an isokinetic protocol designed to improve the participant's knee extensor RTD to allow her to respond more rapidly to balance challenges. Although it is not possible to infer a causal relationship with a case report, it is evident that the participant's strength and function improved after this intervention. As noted in Figure 1B, RTD improved nearly 50% bilaterally. It is interesting to note that after the 12-week intervention, the RTD at the 150 ms time point was roughly the same as the peak torque generated prior to the intervention. This finding suggests that our participant should be able to initiate a compensatory step in a sufficient amount of time to produce a strong response to a loss of balance.39–41 And, although designed to produce improvements in RTD, the strengthening protocol also produced peak isometric torque scores that were 2 standard deviations more than age- and sex-graded normative values.46

After the intervention, scores on both the BBS and TUG exceeded the MDC and placed the participant's performance above, in the case of the BBS, and faster than, in the case of the TUG, the cutoff score for identifying individuals at risk for falls. According to Shumway-Cook et al, “In the range of 54 to 46, a 1-point change in the Berg Balance Scale scores led to a 6% to 8% increase in fall risk.”47 (p817) Using this relationship, the participant's 7-point increase in BBS score approximates a 42% to 56% reduction in fall risk. Previous research on the TUG demonstrated a not unexpected age-related trend toward slower performances for both men and women in the 60- to 90-year-old age range.34 This suggests the utility of using age- and gender-graded data in addition to the absolute fall cutoff time when making clinical judgments with individuals in that age range. After the intervention, the participant's performance on the TUG was not only faster than the cutoff time for identifying individuals at risk for falls but her time was also faster than age- and gender-graded normative values34 for community-dwelling older adults.

In terms of intervention design, the recent meta-analyses by Sherrington et al7,8 identified 3 characteristics of successful structured balance interventions: (1) a total exercise dose of 50 hours, (2) incorporation of moderate- or high-challenge balance exercises, and (3) absence of a walking component. To achieve the 50-hour dosage as rapidly as possible while keeping in mind the limitation of Medicare's therapy treatment cap, the physical therapy intervention for our participant was partnered with line dancing classes. Research has supported dancing as exercise to produce improvements in aerobic power, muscular endurance, dynamic balance, and gait speed in older adults.48 The combination of two 90-minute clinic-based sessions per week, and two 90-minute line dancing sessions per week allowed the participant to easily surpass the 50-hour dose. Also, in keeping with the findings of the meta-analysis, this physical therapy program incorporated dynamic balance drills using progressive decreases in upper extremity support and base of support as well as incorporating dual tasks into the drills. That walking as part of an intervention was not associated with a reduction in fall risk has been interpreted not as a condemnation of walking as exercise, but rather as an understanding that when undertaking fall reduction efforts, the focus of limited training time should initially be on strengthening and balance exercises versus activities like walking which require a lower level of muscular force.49 Pursuant to this, the participant's intervention focused on higher intensity strengthening and balance exercises. The literature does not provide an optimal treatment frequency associated with effective interventions but does suggest that effective programs utilize a standardized format with progressive increases in exercise difficulty to continually challenge the individual.49

A systematic review by Orr et al9 found that strengthening programs for older adults that resulted in improved balance and reduced fall risk utilized a progression from moderate- to high-intensity exercise; however, these programs also resulted in increased risk of injury. The intervention used with this participant utilized isokinetic exercise with angular velocities shown to maximize muscle activation and closely approximate the maximal recruitment found with high isotonic loads, without the injury risk associated with heavy training loads.17 Because of the nature of isokinetic exercise, the exercise resistance was directly proportional to the force-generating capacity of the individual, so that as the individual became stronger, the resistance was concomitantly increased.18 This approach allowed for higher exercise intensity at each treatment session and even within a treatment session than could be accomplished with isotonic exercise progressed at regular intervals.

A number of limitations are inherent in this case. First, the fact that the same physical therapist evaluated, treated, and re-evaluated the participant, provided the opportunity for a positive bias in reporting the outcomes. However, with the possible exception of some individual tasks on the BBS, this limitation is minimized because all other data were objective time or torque measures. Second, as this is a case report documenting the intervention with a single participant, no conclusions can be drawn from the outcomes, and the outcomes cannot be directly generalized to other individuals. It is clear, however, that the participant did in fact benefit from the treatment and measurable improvement was produced by the intervention. Third, not every clinic or practitioner has access to isokinetic equipment, making replication of the resistive protocol difficult. Fourth, the use of a standardized scale such as the Activities-specific Balance Confidence Scale would have provided a more objective measure of the change in the participant's confidence while performing daily tasks. That said, inclusion of the Activities-specific Balance Confidence Scale would not have provided any additional quantification of the participant's fall risk beyond that already provided by the BBS and TUG. Fifth, though the participant had a history of falls, she was diagnosed with nonspecific balance dysfunction so it is impossible to identify the specific mechanisms by which this intervention produced improvement. In addition, the physical therapy program developed for this individual included many aspects beyond isokinetic training. It is possible that the improvements in the outcome measures were due to additional balance training rather than isokinetic training alone. Further research is needed in this area to shed light on the benefits of improving RTD to reduce fall risk.

In conclusion, the individual in this case report had the desire to reduce her fall risk and improve participation in activities of her daily life. She demonstrated changes on the BBS and TUG above that which are considered minimally detectable and which placed her above the fall risk cutoffs for these clinical outcome measures. This individual's peak torque-generating capacity and the rate at which this torque is developed increased by nearly 50% and reported greater confidence with daily activities and improved walking balance.

This case report utilized components, dosages, and intensities obtained from current evidence, coupled with clinical expertise to improve clinical outcomes and reduce fall risk. Clinically, the isokinetic strengthening protocol designed to focus on improving peak torque, and maybe more importantly on improving RTD, led to improvements in clinical outcomes, and the BBS and TUG clinical outcome measures provided reliable and valid measures of function for use in evaluation of the participants and assessing change in response to physical therapy interventions. The results of this case study support the importance of future studies, with a larger sample size to determine the effects of isokinetic training to improve RTD and reduce fall risk in older adults.

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balance and falls; functional outcomes; interventions

Copyright © 2013 the Section on Geriatrics of the American Physical Therapy Association