Resistance training has historically been used as a means to augment muscular hypertrophy, strength, and power for athletic performance. Recently, however, resistance training has become increasingly popular among nonathlete populations for its health benefits, including the prevention and management of osteoporosis (7,15), heart disease (2,4,11), diabetes (3,16), and overall well-being (5). Currently, the use of resistance exercise for health maintenance or improvement remains a novel area of research and one that has direct implication to untrained individuals.
Inevitably, as the benefits of resistance exercise are increasingly recognized, it is becoming more common for researchers and practitioners to test muscular fitness capacities among untrained populations in a field setting. These untrained individuals present a unique challenge to ascertaining reliable data due to an explicit lack of familiarity with testing procedures and experience with maximal effort physical exertion. Maximal strength testing is most often used for evaluating the effectiveness of a resistance training program or to assign loads for specific training objectives through exercise prescription. The 1 repetition maximum (1RM) test is the gold standard of strength measurement and is defined as the maximum amount of weight that can be lifted, pushed, or pulled 1 time (1). However, guidelines for the minimal number of trials needed for reliability in 1RM testing across various untrained populations have not yet been established.
For untrained individuals, single-session testing is not recommended due to the large potential variation between trials (17). As few as 2 trials (12) and as many as 8 trails (13) have been proposed as sufficient to achieve reliable results. The use of prior familiarization sessions before maximal testing has also been recommended to improve test reliability (12). However, in many situations, time and resources are limited, so extensive familiarization may not always be feasible.
In testing environments where time and resources are limited, it is advantageous to obtain a reliable measurement of maximal strength as expeditiously as possible. Unfortunately, if too few trials are employed, consistent measures may not be obtained, whereas with too many trials, resources can be wasted. Furthermore, especially among untrained individuals, although consistency may be enhanced by multiple repeated tests, the potential for a carryover training effect is also increased. It would therefore be of assistance to practitioners to identify the least number of trials needed to obtain a consistent measure of maximal strength for various populations. Thus, the purpose of this study was to evaluate differences between multiple 1RM chest and leg press trials in healthy previously untrained women to determine the minimal number of trials needed to obtain a reliable measurement of maximal strength. Our hypothesis was that 3 trials would be sufficient, with trial 1 serving as a familiarization session, and that a consistent measure of upper- and lower-body maximal strength would be obtained between trials 2 and 3.
Experimental Approach to the Problem
The present study was undertaken to evaluate the consistency of 1RM test results in untrained women without additional prior familiarization sessions. To do so, we analyzed data from 3 maximal strength trials that utilized a standardized testing procedure to ensure test-retest repeatability. Standardization of the test protocol was considered to be essential because participants lacked prior familiarity with either the chest or the leg press procedure. The test protocol recommended by Kraemer et al. (6) was identified as the most appropriate for this population because it allowed the tester to quantify load (i.e., 40 and 60% perceived maximum) after completion of the first trial.
Twenty women between the ages of 24 and 54 years volunteered to participate in the study. Body mass index (BMI) ranged from 21.1 to 39.5. All were in good health and denied heart disease, diabetes, or hypertension. Although some participants reported regular physical activity (Table 1), none engaged in a regular resistance exercise program, so all were considered “untrained” for the purposes of this study. One participant was excluded from the study during the testing process due to quadriceps muscle pain at trial 2 that prevented completion of the testing protocol. The remaining 19 participants (mean age 35.5 ± 2.1 years; mean BMI 28.3 ± 1.2 kg·m−2) (Table 1) completed all strength trials. There was no correlation between age and BMI (r = −0.32; p = 0.18). The study was approved by the Institutional Review Board of Arizona State University.
Maximal strength was measured using an adaptation of the 1RM procedure described by Kraemer et al. (6). A series of 3 1RM tests were scheduled at least 24 hours apart. During each trial, the greatest weight lifted or pressed for each exercise (chest press and leg press) was identified as the 1RM. Each repetition commenced from a position just short of full extension. Participants lowered the weight until a 90° angle of the elbow (chest press) or knee (leg press) was reached and then immediately raised it again to the starting position. Failure was identified as the participant's inability to lower the weight to a full 90° joint angle or return it successfully to the starting position.
All strength testing was conducted by the principle investigator. Participants were requested to report to the physical activity center having eaten a regular meal no more than 2 hours prior to testing. If they had not eaten a meal, they were instructed to eat a light snack of approximately 150 cal, including some protein, within 30-60 minutes of the test session. None of the participants were familiar with the 1RM test procedure. Familiarization was incorporated into the first 1RM trial and was reviewed as needed during the second trial. By the third trial, all participants demonstrated understanding and comfort with the exercises and the test procedure. Appropriate breathing technique was emphasized during all testing to avoid the Valsalva maneuver.
Following 2 warm-up sets of 5-10 repetitions at 40% of the estimated 1RM and 3-5 repetitions at 60% of the estimated 1RM, participants were asked to lift their perceived maximum weight 1 time. If the lift was completed successfully, a small amount of weight (chest press: 5-10%; leg press: 10-20%) was added and the participant was asked to attempt to lift the additional weight 1 time. A rest period of 2-3 minutes was provided between all maximal attempts with the goal being to achieve the 1RM within 3-5 attempts (6). For the first trial, it was necessary to estimate an appropriate weight for calculation of the warm-up sets and first maximal attempt. However, for subsequent trials, the 1RM identified in the previous trial was used. To better gauge intensity in these untrained individuals, participants were asked to rate each lift using a rating of perceived exertion (RPE) on a scale of 1-10 as suggested by McGuigan and Foster (8). For purposes of testing, a maximal attempt was defined as actual failure or an RPE of 9-10 with a statement by the participant that another attempt could not be achieved.
Data were analyzed using SPSS version 14.0. Differences in maximal strength between individual trials were analyzed for significance using repeated measures analysis of variance. Paired t-tests were performed to identify specific differences between trials 1-2, 2-3, and 1-3. An alpha level was set at p < 0.05. Intraclass correlation (ICC) analysis was used to evaluate test-retest reliability, and Pearson correlations were analyzed for age, BMI, and strength outcomes.
To promote familiarization, the goal was to complete all testing sessions within 1 week, including weekend days. The average number of days was 2.6 ± 0.4 (SE) between trials 1 and 2, and 3.1 ± 0.4 (SE) between trials 2 and 3 (Table 2). For the 1RM leg press, significant increases in maximal strength were seen between all trials, although no significant changes were seen between any trials for the 1RM chest press. Maximal strength increases between trials 1-2 and 2-3 were 6.9 ± 0.6 kg (p = 0.05) and 7.3 ± 0.4 kg (p = 0.01), respectively, for the leg press, while the difference between trials 1-3 was 14.2 ± 1.0 kg (p < 0.01) (Table 2). For the chest press, maximal strength increases between trials 1-2 and 2-3 were 1.2 ± 0.3 kg (p = 0.13) and 1.3 ± 0.4 kg (p = 0.18), respectively, while the increase between trials 1 and 3 was 2.5 ± 0.7 kg (p = 0.06) (Table 2). Although significant differences between trials were found, test-retest reliability for both upper- and lower-body maximal strength testing was strong. The calculated ICC and 95% confidence interval (CI) for both 1RM chest press (r = 0.95; CI: 0.90-0.98) and 1RM leg press (r = 0.95, CI: 0.89-0.98) were highly significant (p < 0.0001).
No correlation was found between age and maximal strength changes in leg press (r = −0.25, p = 0.30) or chest press (r = −0.12, p = 0.64), nor was there a correlation between BMI and strength changes in leg press (r = 0.13, p = 0.60) or chest press (r = 0.19, p = 0.43). In addition, there was no correlation between age or BMI and absolute 1RM scores for either the leg press (age: r = −0.32, p = 0.18; BMI: r = 0.38, p = 0.11) or the chest press (age: r = −0.29, p = 0.22; BMI: r = 0.42, p = 0.07).
Reliability has not been well studied in relation to maximal strength testing. When working with athletic populations who are highly familiar with the test exercises, a presumption of accuracy with 1 or 2 trials may be appropriate. However, as more interest is given to untrained nonathletic populations, obtaining a consistent measure of maximal strength as efficiently as possible will be of great importance. Too few trials may not produce a true value of muscular strength, which could negatively affect research findings or training program results, while too many trials will inevitably waste valuable time and resources.
The current study contributes to the literature in several ways. First, these data provide support for the incorporation of familiarization into an initial testing session, rather than utilizing resources for exclusive familiarization sessions prior to actual strength testing. Second, the study highlights potential differences in upper- and lower-body test results. For untrained women, there appears to be a significant difference in upper- and lower-body responses to testing. Further, as there was no relationship found between either age or BMI and strength changes between trials, differences do not appear to be dependent on individual characteristics.
Our findings are consistent with those of Phillips et al. (12) who also found no significant difference in maximal upper-body strength but a statistically significant difference in lower-body strength across 3 trials of 1RM chest press and leg press in untrained elderly women. However, Phillips et al. (12) conducted at least 3 familiarization sessions prior to testing. This is a time-consuming and potentially costly process that, based on our present findings, does not achieve a greater degree of test-retest reliability than integration of familiarization into the first 1RM trial.
Conversely, our study does not support the findings of Ploutz-Snyder and Giamis (13) that older women require a greater number of trials for consistent measurement of lower-body strength than younger women. Although both our study and that of Ploutz-Snyder and Giamis support the need for greater than 3 trials to achieve consistent measures of lower-body strength, we did not find any relationship between age and strength changes for either lower or upper body. This may be due to the fact that Ploutz-Snyder and Giamis (13) evaluated changes in leg extension strength, an exercise that isolates a single muscle group, rather than the more complex multi-joint leg press used in the current study that activates multiple muscle groups. This may have provided some benefit for younger women that influenced the significant age difference identified by Ploutz-Snyder and Giamis. However, because the criterion for retesting was ≥1-kg increase in strength from the prior test, it is difficult to truly evaluate the significance of the difference between trials, as 1 kg represents approximately 1% of the final 1RM obtained for older women and 0.7% of the final 1RM obtained for young women. Furthermore, in young women, an average of 3.6 trials resulted in an overall 12% increase in strength, while in older women, an average of 8.8 trials resulted in a 21% increase in strength. While a 1-kg increase may or may not be significant, it is possible that a similar number of trials would have resulted in similar overall increases in strength for both young and old women. If so, this would be consistent with our present findings that 3 trials of maximal lower-body strength testing resulted in approximately a 14% increase in strength for all participants, regardless of age.
Recently, Schroeder et al. (14) evaluated 2 trials of 1RM chest and leg press in untrained elderly men and found no change in maximal strength between trials for either upper or lower body. These are unique findings and are not consistent with any of the earlier research in this area. This may be due to the use of pneumatic equipment for testing that recorded strength as Newtons rather than more traditional measurement of resistance in pounds or kilograms. In addition, Schroeder et al. (14) scheduled trials 7-10 days apart, whereas in the current study, rest days between trials were limited to 2-3 (±0.4). It is our belief that either the prolonged rest between trials or the use of pneumatic equipment to quantify strength may have served as a confounder for the study of Schroeder et al. (14) that eliminated strength differences between trials as well as between upper- and lower-body muscle groups.
Although further work is needed in this area, there is general agreement between our study and that of previous research (12). For upper-body maximal strength testing in untrained women, 3 trials are sufficient to achieve a consistent measurement. However, for lower-body testing, with or without prior familiarization, 3 trials are not sufficient for consistency. Furthermore, our results and that of Phillips et al. (12) are in agreement with Ploutz-Snyder and Giamis (13) that, at least for lower-body strength measurement in women, a minimum of 4 and possibly as many as 8 trials may be needed.
Although no mechanism for the difference between upper- and lower-body testing has been clearly identified, Phillips et al. (12) proposed a delayed learning effect for the leg press, which resulted in a significant difference between trials. This may be related to the larger absolute muscle mass of the lower body compared with that of the upper body, especially in women (9). Although both the chest press and the leg press are complex, multi-joint exercises, the absolute muscle mass activated by the leg press is greater than that of the chest press. Neural adaptation (10) may occur more rapidly when smaller numbers of muscle fibers are engaged, resulting in less change between trials in the chest press than the leg press.
When testing untrained women, 3 trials of upper-body maximal strength testing are sufficient to obtain a reliable measurement of strength. Furthermore, familiarization can be effectively incorporated into trial 1 to increase efficiency. However, 3 trials regardless of prior familiarization sessions may not be sufficient to obtain a reliable measure of lower-body maximal strength in untrained women. If feasible, successive trials of strength measurement should be compared and adjusted so as to achieve consistent values prior to developing training protocols. To date, research in this area has been limited, especially with untrained individuals. Further work is needed to establish the appropriate number of trials needed for efficient and accurate maximal strength testing for both lower- as well as upper-body musculature. Until such time as that work has been done, researchers and practitioners should routinely report the number of trials used for maximal strength measurement to allow others to appropriately evaluate their findings.
1. American College of Sports Medicine. Physical fitness testing and interpretation. In: ACSM's Guidelines for Exercise Testing and Prescription
. 6th ed. Franklin, BA, Whaley, MH, and Howley, ET (eds.). Baltimore: Lippincott Williams & Wilkins, 2000. pp. 57-90.
2. Benton, MJ. Safety and efficacy of resistance training in patients with chronic heart failure: Research-based evidence. Prog Cardiovasc Nurs
20: 17-23, 2005.
3. Cohen, ND, Dunstan, DW, Robinson, C, Vulikh, E, Zimmet, PZ, and Shaw, JE. Improved endothelial function following a 14-month resistance exercise
training program in adults with type 2 diabetes. Diabetes Res Clin Pract
79: 405-411, 2008.
4. Dejong, AT, Womack, CJ, Perrine, JA, and Franklin, BA. Hemostatic responses to resistance training in patients with coronary artery disease. J Cardiopulm Rehabil
26: 80-83, 2006.
5. Dionigi, R. Resistance training and older adults' beliefs about psychological benefits: The importance of self-efficacy and social interaction. J Sport Exerc Psychol
29: 723-746, 2007.
6. Kraemer, WJ, Ratamess, NA, Fry, AC, and French, DN. Strength training: Development and evaluation of methodology. In: Physiological Assessment of Human Fitness
(2nd ed). P.J. Maud and C. Foster, eds. Champaign, IL: Human Kinetics, 2006. pp. 115-138.
7. Martyn-St James, M and Carroll, S. High-intensity resistance training and postmenopausal bone loss: A meta-analysis. Osteoporos Int
17: 1225-1240, 2006.
8. McGuigan, MR and Foster, C. A new approach to monitoring resistance training. Strength Cond J
26: 42-47, 2004.
9. Miller, AE, Macdougall, JD, Tarnopolsky, MA, and Sale, DG. Gender differences in strength and muscle fiber characteristics. Eur J Appl Physiol Occup Physiol
66: 254-262, 1993.
10. Moritani, T and Devries, HA. Neural factors versus hypertrophy in the time course of muscle strength gain. Am J Phys Med
58: 115-130, 1979.
11. Olson, TP, Dengel, DR, Leon, AS, and Schmitz, KH. Moderate resistance training and vascular health in overweight women. Med Sci Sports Exerc
38: 1558-1564, 2006.
12. Phillips, WT, Batterham, AM, Valenzuela, JE, and Burkett, LN. Reliability of maximal strength testing
in older adults. Arch Phys Med Rehabil
85: 329-334, 2004.
13. Ploutz-Snyder, LL and Giamis, EL. Orientation and familiarization to 1RM strength testing in old and young women. J Strength Cond Res
15: 519-523, 2001.
14. Schroeder, ET, Wang, Y, Castaneda-Sceppa, C, Cloutier, G, Vallejo, AF, Kawakubo, M, Jensky, NE, Coomber, S, Azen, SP, and Sattler, FR. Reliability of maximal voluntary muscle strength and power testing in older men. J Gerontol A Biol Sci Med Sci
62: 543-549, 2007.
15. Shackelford, LC, Leblanc, AD, Driscoll, TB, Evans, HJ, Rianon, NJ, Smith, SM, Spector, E, Feeback, DL, and Lai, D. Resistance exercise
as a countermeasure to disuse-induced bone loss. J Appl Physiol
97: 119-129, 2004.
16. Sigal, RJ, Kenny, GP, Boule, NG, Wells, GA, Prud'homme, D, Fortier, M, Reid, RD, Tulloch, H, Coyle, D, Phillips, P, Jennings, A, and Jaffey, J. Effects of aerobic training, resistance training, or both on glycemic control in type 2 diabetes: A randomized trial. Ann Intern Med
147: 357-369, 2007.
17. Symons, TB, Vandervoort, AA, Rice, CL, Overend, TJ, and Marsh, GD. Reliability of a single-session isokinetic and isometric strength measurement protocol in older men. J Gerontol A Biol Sci Med Sci
60: 114-119, 2005.