Validity and Reliability of Measurements of Elbow Flexion Strength Obtained from Older Adults Using Elastic Bands

Journal of Geriatric Physical Therapy, 2006 by Manor, Brad, Topp, Robert, Page, Phil

ABSTRACT

Purpose: This study determined the validity and reliability of measurements of elbow flexion strength obtained from older adults using elastic bands. Methods: Forty-eight community-dwelling older adults with documented functional limitations completed 3 assessments of elbow flexion strength: a 30-second test using elastic bands to generate resistance, a similar test using dumbbells, and a test using an isokinetic dynamometer. One week later, subjects repeated the 30-second elbow flexion test using elastic bands. Results: The 30-second elbow flexion test using elastic bands was significantly correlated with both the 30-second elbow flexion test using dumbbells (r = 0.62, P

Key Words: Theraband�, muscle strength, measurement, aging

INTRODUCTION

Normal biological aging is accompanied by losses in functional ability and independence.1 These age-related reductions have been linked to numerous interconnected factors,2 and are responsible for a host of clinically important problems such as falls3,4 and osteoarthritis.5 Precipitating the age-related decline in functional ability is a concomitant decline in skeletal muscle mass and voluntary strength,2 which has been shown to be mitigated by resistance training.6-8

The influence that muscular strength has on functional ability in later life has resulted in the development of a variety of methods for measuring strength. For instance, the American College of Sports Medicine9 describes one repetition maximum (1RM) and 6-8 RM isotonic protocols using machines as well as free weights. However, these methods of assessing strength lack portability and may be inappropriate with some groups of functionally limited older adults. Isokinetic dynamometer systems such as the KinCom (Chattecx, Chattanooga, Tenn) or Biodex (Biodex Medical, Shirley, NY) provide a detailed description of isometric and or isokinetic strength parameters;6,10 however, these dynamometers are often impractical for testing or training in the community and may pose a health risk to older adults presenting with cardiovascular disease.11

In response to these challenges in documenting gains in muscular strength in older adults, Rikli and Jones12 developed an assessment of upper body muscular strength based on the number of times a dumbbell of standard weight can be curled through full range of motion over a 30-second time period (dumbbell weighted elbow flexion). While this assessment does not involve a single maximal effort and therefore incorporates a component of muscular endurance, it nevertheless validly and reliably assesses upper limb strength among older adults. Further, it may be more sensitive to training-related improvements, as dumbbells or other hand weights are frequently employed as a mode of generating resistance during resistance training among older adults.13

Recently, the utilization of elastic bands as a mode of generating resistance during resistance training has gained popularity in the clinical and research settings. This form of resistance training has proven beneficial in older adults,14-16 and the inherent properties of the elastic band material may better accommodate the length-tension characteristics of normal joint and muscle actions.17 Therefore, the development of a method of assessing muscular strength using elastic bands may be more sensitive to gains resulting from this type of training. The purpose of this study was to determine the validity and reliability of measurements of elbow flexion strength obtained from older adults using elastic bands. The researchers hypothezised that performance in the 30-sec band test (elastic band resisted elbow flexion) would be significantly correlated with performance measured using the dumbbell weighted arm curl test and the isokinetic dynamometer, and that it would demonstrate high test-retest reliability.

METHODS

Participants

Adults over the age of 65 (40 women, 8 men; age = 73.0 � 6.7 years), who provided informed consent prior to participating in the study, were recruited from an ongoing study approved by the human research committee at The University of Toledo. Inclusion criteria for this study included being 'functionally limited/as defined by: (1) scoring below the population segment average on the Physical Functioning Subscale of the MOS Short Form (SF) -36,18 and (2) performing below the population segment mean for climbing 26 stairs.19 All subjects were also screened by a physician for the presence of any condition that would contraindicate their participation in a program of regular physical exercise.9

Design

Initially, all subjects underwent 3 assesssments of elbow flexion strength during a single visit to the exercise laboratory of a midwest university. All testing procedures were conducted by a single, trained administrator. Prior to testing procedures, subjects performed a warm-up consisting of walking 1 lap around an indoor track (approximately 175 meters) at a selfselected pace, and 25 unweighted elbow flexion movements against gravity. The first 2 assessments were the Rikli & Jones test of elbow flexion strength using a dumbbell (males = 3.6 kg, females=2.3 kg), and the elastic bands test using Thera-Band� (The Hygenic Corporation, Akron, Ohio) [males = blue (3.2 kg), females = green (2.3 kg)].20 The final assessment consisted of maximal-effort elbow flexion using a KIN-COM 500H isokinetic dynamometer. These assessments were administered on the same day and in the same order to all subjects. In order to minimize the effects of fatigue, at least 15 minutes were provided between each assessment.21 One week following the first session, subjects (n = 38) again performed the elastic band resisted elbow flexion protocol using the same color elastic band to generate resistance. During the intervening time period, subjects were instructed to maintain current levels of daily activity.