The reliability of the 1RM strength test for untrained middle-aged individuals

Summary

The one-repetition maximum (1RM) test is considered the gold standard for assessing muscle strength in non-laboratory situations. Since most previous 1RM reliability studies have been conducted with experienced young participants, it is unclear if acceptable test–retest reliability exists for untrained middle-aged individuals. This study examined the reliability of the 1RM strength test of untrained middle-aged individuals. Fifty-three untrained males (n = 25) and females (n = 28) aged 51.2 ± 0.9 years participated in the study. Participants undertook the first 1RM test (T1) 4–8 days after a familiarisation session with the same exercises. 1RM was assessed for seven different exercises. Four to eight days after T1, participants underwent another identical 1RM test (T2). Ten weeks later, 27 participants underwent a third test (T3). Intraclass correlation coefficients (ICC), typical error as a coefficient of variation (TEcv), retest correlation, repeated measures ANOVA, Bland–Altman plots, and estimation of 95% confidence limits were used to assess reliability. A high ICC (ICC > 0.99) and high correlation (r > 0.9) were found for all exercises. TEcv ranged from 2.2 to 10.1%. No significant change was found for six of the seven exercises between T1 and T2. Leg press was slightly higher at T2 compared to T1 (1.6 ± 0.6%, p = 0.02). No significant change was found between T2 and T3 for any exercise. 1RM is a reliable method of evaluating the maximal strength in untrained middle-aged individuals. It appears that 1RM-testing protocols that include one familiarisation session and one testing session are sufficient for assessing maximal strength in this population.

Introduction

Resistance training has been of great interest to exercise scientists and health professionals who study both healthy individuals, and those who suffer from chronic conditions including cardiovascular diseases,1, 2, 3 diabetes mellitus,4, 5 and overweight/obese individuals.⁶ Since an increase in muscle strength is the most common and important benefit of resistance training,7, 8 an accurate determination of muscle strength to properly evaluate the efficacy of the training is essential.⁹ Laboratory-based methods for evaluating maximal muscle strength include the use of isometric dynamometers10, 11 and isokinetic dynamometers.12, 13, 14 These two methods, however, usually require sophisticated laboratory equipment and personnel trained in their use. Furthermore, these tests are not very specific for the types of movement patterns commonly used in typical fitness regimes. In contrast, the one-repetition maximum (1RM) method, defined as the maximal weight that can be lifted once with correct lifting technique, is comparatively simple and requires relatively inexpensive non-laboratory equipment.⁹ Moreover, because the 1RM test can be performed using the same patterns as those undertaken by the exercising individuals during their normal training, it is increasingly gaining acceptance as the gold standard for assessing muscle strength.8, 9 Furthermore, previous studies have reported that the 1RM method to assess muscle strength is safe for healthy adults15, 16 and also for patients with cardiovascular disease.17, 18 The test–retest reliability of the 1RM demonstrates high intraclass correlation coefficients (ICC). However, as most 1RM reliability studies have been conducted with experienced healthy young participants (age 18–30 years),19, 20, 21 it is unclear whether this test–retest reliability is applicable to untrained middle-aged individuals who are increasingly the subject of exercise intervention studies. It has been suggested that the reliability of strength tests in older populations may be lower due to decreased muscle strength and joint stability.¹² To date, there is a lack of data on the test–retest reliability of 1RM tests performed by untrained middle-aged individuals for a range of different resistance exercises. Most studies that have examined the test–retest reliability of maximal strength in middle-aged and older populations have used isokinetic dynamometers12, 22, 23 and not isoinertial-based (gym) machines.

A familiarisation process prior to 1RM strength testing is essential for ensuring reliable test results24, 25 and minimize learning effect or systematic bias.²⁶ Furthermore, it has been shown that without a familiarisation process prior to strength testing, there is a significant increase in the expression of muscle strength between two consecutive strength tests performed a few days apart.24, 25 Some investigators have suggested that older individuals should undergo between 8–9 sessions of 1RM testing in order to increase the consistency of the 1RM measurements.²³ Multiple familiarisation sessions, however, may not be practical for training studies that examine strength changes for several different resistance exercises as well as numerous other functional parameters. This would unnecessarily increase the time requirement of each participant and extend the duration of the study, both of which might increase the likelihood of participant dropout. As such, the purpose of this study was to examine the test–retest reliability of the 1RM strength test of untrained middle-aged individuals following one familiarisation session.