CTRI

Muscle strength as well as endurance have been highlighted as important components associated with health-related fitness in individuals of all age groups. On one hand, muscle strength is the ability to exert maximal force whereas muscle endurance refers to the ability to perform prolonged muscular work at predetermined intensity without external signs of fatigue. These two indices, when taken together, have been shown to provide an almost complete measure of muscle performance. There has been an increasing focus on the interchangeability of muscle performance related tests in conditions of age-related, disease-related or resource-related constraints. Modified methods often need to be validated and correlated with the existing reliable methods in order to utilize these alternative testing options. The hand grip dynamometer is a simple instrument that has been used widely for evaluating muscle strength and in more recent times, muscle endurance. There is lack of a standard protocol for evaluating muscle endurance in these studies employing dynamometry. Moreover, these protocols have not been correlated with any existing methods used for upper limb endurance testing. Therefore, it has been planned to establish and validate a standard protocol for evaluating muscle endurance using hand grip dynamometer.

The aim of the present study is to evaluate whether hand grip dynamometer can be used to test muscle endurance in adults. Participants who meet the inclusion and exclusion criteria will be further screened before the main study. The general information, anthropometric measurements and physical examination findings will be recorded for each participant during the screening visit. The physical activity and cardiorespiratory fitness will also be evaluated for all eligible participants during this visit. Only those participants who fall in low or moderate category of physical activity and whose values of maximal oxygen uptake fall within a specified range (30-60 mL/kg/min) will be considered eligible for the main study. For the main study, after following adequate precautions, each participant will have to perform 3 tests for muscle endurance:

1. Six-minute walk test (6MWT): Participants will be asked to walk for 6 minutes at their own pace while being monitored closely. The distance walked will be taken as the endpoint.

2. Push-up test: Depending upon their gender, participants will be asked to perform push-ups according to the standard protocol (men) or modified protocol (women) till exhaustion. The number of push-ups will be taken as the endpoint.

3. Hand grip dynamometry: After explaining the testing position for electronic hand grip dynamometer, different protocols will be employed to assess the static as well as dynamic muscle endurance.

a) Static endurance: Duration for which the participant can maintained a desired target contraction (either 50% or 60% of maximum voluntary contraction) will be taken as endpoint.

b) Dynamic endurance: Two approaches for evaluating dynamic endurance will be used. First, each participant will be asked to repeatedly squeeze the dynamometer at a fixed rate till exhaustion (duration will be taken as endpoint). Second, participants will be instructed to squeeze the dynamometer will maximal effort for 8,10 or 12 repetitions at 15 second intervals (fatigue index will be taken as endpoint).

Adequate precautions will be taken during the conduct of each study and participants will be given sufficient rest period between different tests. The levels of perceived exertion (using Borg CR-10 scale) and muscle soreness (using visual analogue scale) will be evaluated before the start of and immediately after each test. For evaluating repeatability, all tests will be repeated twice in the same order in the following 4 weeks (ensuring at least one-week

interval between each visit).