Andre Nyberg1*, Britta Lindström1, Nils Aronsson1, Magnus Näslund1 and Karin Wadell1,2
1Department of Community Medicine and Rehabilitation, Physiotherapy. Umeå University, Umeå, Sweden
2Department of Public Health and Clinical Medicine, Division of Medicine, Umeå University, Umeå, Sweden
Received: 12 April, 2016; Accepted: 27 April, 2016; Published: 28 April, 2016
Andre Nyberg, Department of Community Medicine and Rehabilitation, Physiotherapy. Umeå University, 90187 Umeå, Sweden, Tel: + 46 90 786 6639; Fax: + 46 90 786 9267; E-mail:
Nyberg A, Lindström B, Aronsson N, Näslund M, Wadell K, et al. (2016) Validity of using Elastic Bands to Measure Knee Extension Strength in Older Adults. J Nov Physiother Phys Rehabil 3(1): 016-021. DOI: 10.17352/2455-5487.000030
© 2016 Nyberg A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Elastic bands; Knee extension; Maximal strength; Older adults; One-repetition maximum; Validity
1-RM: One-Repetition Maximum; ICC: Intraclass Correlation Coefficient; LoA; Limits of Agreement; R: Pearson’s Correlation; Rc: Concordance Correlation Coefficients
Background and objectives: Maximal strength assessment of knee extensors in older adults using elastic resistance bands have rarely been addressed even though resistance training using elastic bands have shown large effects on muscle strength in this group of people. We therefore aim to determine the validity of maximal knee extension strength assessment using elastic resistance bands in older women and men.
Methods: Twenty-four participants (12 women and 12 men; 61.8 ± 6.0 years; 173.5 ± 10.2 cm; 71.9 ± 15.7 kg) were included. To assess maximal knee extension strength, participants performed one-repetition maximum testing of concentric knee extension using elastic resistance bands as well as a maximal concentric knee extension isokinetic test at 60°/s using a stationary isokinetic dynamometer. Concurrent validity of the two measurement techniques were assed using intraclass correlation coefficient (ICC2.1), Pearson correlations (R), concordance correlations (Rc) and by determining variations on an individual level using 95% limits of agreement (LoA) with isokinetic dynamometry measurement as the reference standard.
Results: Validity analysis showed good to excellent agreement and relationships but wide 95% LoA between elastic one-repetition maximum and isokinetic peak torque for all participants (ICC = 0.88; R = 0.90; Rc = 0.85, LoA = 10.5 kg), for women (ICC = 0.67; R = 0.77; Rc = .62, LoA = 7.7 kg) and for men (ICC = 0.80; R = 0.85; Rc = 0.78, LoA = 13.1 kg), respectively.
Conclusion: One-repetition maximum testing using elastic resistance bands provides valid measurements of maximal knee extension strength in older women and men but with wide variations on an individual level.
Knee extension strength is an important component of physical fitness, it has an independent role in the prevention of chronic diseases and muscle weakness is strongly related to functional limitations and physical disabilities. Knee extension strength is also inversely associated with all-cause mortality, independent of confounding factors such as level of physical activity and cardiorespiratory fitness in both elderly as well as in people suffering from chronic diseases [1,2]. If the goal is to improve knee extension strength, resistance training programs are one of the most popular forms of exercise . Resistance training is also recommended before other available exercise modalities as it is considered the most effective way to improve muscle strength and can be performed using a variety of exercise equipment .
One such exercise alternative is elastic resistance equipment such as elastic bands and tubing which has been found effective in increasing muscle strength in older adults [3,5,6] offering an inexpensive and portable exercise equipment that is easy to use. It is also more accessible than other exercise equipment’s such as isokinetic dynamometers or weight machines [7-9]. In a similar way as resistance training could be performed using different exercise equipment, evaluation of resistance training programs can be performed using a variety of measurement equipment, from uncomplicated functional tests to advanced laboratory tests [10-12]. Of importance is that the assessment of muscle function, in addition to being muscle group-specific, also is heavily dependent on the type of contraction, velocity of movement and equipment used . In a similar way as exercise training adaptations are specific to the stimulus applied, the most sensitive method of assessing exercise induced adaptations has been found when the method of assessment is as comparable as possible to the exercise modality used. Thus, the most sensitive method of assessing the effects of resistance training performed using elastic bands is an assessment method that also employs elastic bands . In the assessment of muscle strength, the 1-repetition maximum (1-RM) test has been described as the “gold standard” for isotonic maximal muscle strength measurements  and is considered a reliable and valid measurement technique to evaluate knee extension strength in older adults using weight machines [15,16]. The validity of using elastic resistance bands to evaluate muscle strength in older adults has rarely been addressed, especially including a component of maximal effort such as a 1-RM test. It could be argued that the increase in the length of an elastic band, which occurs in any dynamic movement, will result in a progressive increase in resistance making accurate evaluations of 1-RM difficult [17,18]. However, the definition of 1-RM has previously been adopted with the use of elastic resistance bands  and our group have previously found that 1-RM using elastic bands is a valid method to measure shoulder flexion strength in older women and men .
To our knowledge, no previous study has investigated the use of 1-RM testing with elastic resistance bands to determine the maximal knee extension strength in older adults. The purpose of this study was to investigate the concurrent validity of a 1-RM test with elastic resistance bands in the measurement of knee extension maximal strength by evaluating the intraclass correlation coefficient (ICC) absolute agreement, correlations, and variations at an individual level using 95% limits of agreement (LoA) with isokinetic dynamometry testing as the reference standard. It was hypothesized that the elastic 1-RM test would demonstrate good validity for the assessment of knee extension strength (ICC > 0.61).
Material and Methods
Twenty-four participants (61.8 ± 6.0 years; 173.5 ± 10.2 cm; 71.9 ± 15.7 kg; 12 women) were included in the study. Tests were performed in our exercise lab at the Department of Community Medicine, Physiotherapy, Umeå University, Umeå, Sweden.
To be eligible for participation in the study, participants had to be 50 years of age or older, without any current musculoskeletal disorders that would prevent them from performing a maximal concentric contraction during knee extension using their dominant (preferred) leg. The participants were asked not to perform strength training or any other activity that would physically exert their lower extremities within 24 hours leading up to the tests. The regional ethics board, Umeå, Sweden, approved the study (Reg. No. 2012-60-32M), and participants gave written informed consent prior to participation.
Isokinetic dynamometry testing is thought to provide the most accurate assessment of muscular strength and has previously been used to determine the validity of using elastic resistance bands to measure muscle strength [10,20,21]. The participants performed concentric maximal contractions in an isokinetic dynamometer (Kin-Com ®, Chattanoga Group, Inc) and 1-RM (that is, the maximum weight that could be lifted by a person in a single bout in the whole-range of movement) using elastic resistance bands (Thera-Bands, The Hygenic Corporation, Akron, OH, USA). At first, the participants were informed on the procedures of the tests. Thereafter, a five minute warm-up on an electronically braked cycle ergometer (Monark 818E, ergomedic, Sweden ®) at a submaximal load and cadence was performed. The Borg Scale of perceived exertion , was used and the participants were instructed to adjust the load between 11 and 13 on the scale with a cadence of 60 RPM, automatically controlled by the cycle ergometer.
The starting point of the two tests was set to 90° of knee flexion, the end point for both tests was set to approximately five degrees below the maximum point of active knee extension for each participant. Standardized instructions and standardized verbal encouragement were given during both tests to facilitate a maximal effort , no visual feedback was provided. The same two test administrators (both male) conducted all tests, and both tests were performed during a single 60 minute visit for each participant (time of day: between 09:00-18:00). A pre-specified percentage of the peak torque value of 80% from the isokinetic test was used to determine the starting load for the 1-RM elastic band test. This meant that no randomization of exercise order was possible, resulting in each test session starting with the isokinetic test.
Isokinetic assessment of knee extension strength was performed with the dominant leg using a stationary dynamometer (Kin-Com ®, Chattanoga Group Inc) at an angular velocity of 60°/s. Data were acquired using a PC and Kin-Com ® software and digitally stored (12 bits, Mysas, Department of Biomedical Engineering & Informatics, University Hospital, Umeå, Sweden). Isokinetic measurements of knee extension strength using a Kin-Com at 60°/s have previously demonstrated excellent test-retest, intra- and inter-rater reliability (ICC = 0.90, 0.98 and 0.93, respectively) . The test administrator performed a demonstration of the test before the participants were placed in the isokinetic dynamometer. The participants were fixated at the trunk, hip and distally on the tested leg with straps to minimize any compensatory body movements. The movement center of the isokinetic dynamometer was aligned with the lateral condyle (femur) of the tested leg. The participants were seated in the chair with the back rest at an angle of 100°. The seat was adjusted to a slight upward angle. The chair and dynamometer were positioned for knee extension movement assessment according to the specifications of the manufacturer with a standardized starting position (the starting point of the isokinetic dynamometer) of 90° flexion of the knee joint (Figure 1 A). The angular velocity was set to 60°/s for both the concentric (knee extension) and eccentric phase (knee flexion) of the movement. The participants then performed two sets of five submaximal repetitions to familiarize themselves with the equipment and testing procedure and to acquire additional warm up [10,24]. At the time of the test the participants were instructed to exert themselves maximally during the concentric phase and to relax during the eccentric phase. The test consisted of five maximal repetitions performed consecutively as previously used to measure 1-RM using elastic resistance bands in older adults . The maximum value out of the five contractions were used to determine isokinetic peak torque.
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