An exponential model of isometric muscular fatigue as a function of age and muscle groups

Abstract

Despite the recommendations that an important design criterion is not to exceed 15% of an operator's maximum voluntary contraction (MVC) with any muscle that must be used for a long period of time, many tasks involve the exertion of much higher forces coupled with long-term contractions. Many studies have investigated the force-time relationship of isometric muscle contractions to determine the endurance time of a given relative force. To date, however, direct studies of muscle performance throughout fatiguing tasks have not been conducted to the same degree. This research was concerned with studying the effects of different muscle groups (biceps vs quadriceps) of subjects with different age groups (20-29 vs 50-59 years of age) on long-term muscular isometric contractions at different levels of %MVC (20%, 40%, 60%, 80%, and 100% MVC), and modelling the functional data to describe the time course of strength decrement. The data revealed that the time course of strength decrement was best modelled by the function: [formula: see text] An experiment, using 20 subjects with each subject performing 10 conditions (two muscle groups x five levels of %MVC), showed that this function accounted for over 95% of the variance of strength decrement. All parameter estimates were statistically significant.

Habitual level of physical activity and muscle fatigue of the elbow flexor muscles in older men

“…Generalization of such formulas for a population of older subjects therefore requires great caution. Although a direct comparison between young and old is not possible, as young subjects were not included in this study, our results support the findings of other studies reporting a longer endurance time in aged subjects (Bilodeau et al 2001b) and in particular at low contraction forces (Deeb et al 1992). The changes in muscle fibre composition (atrophy of type II fibres) with ageing, and the decreased ability of older subjects to activate their muscles voluntarily already mentioned, could help to explain the observation of longer endurance times (Bilodeau et al 2001b).…”

“…Using Rohmert's formula, the predicted endurance time would be 222 s, which is about half the value from our test results. This discrepancy between studies may be related to several factors including the age of the subjects and the different methodologies and equipment used (Deeb et al 1992). The results in Rohmert's study are based on young subjects, while in this study the participants were over the age of 55 years.…”

The time variation pattern of mechanical exposure and the reporting of low back pain

“…46 S. Krajcarski and R. Wells Similar trends have also been found in physiological responses to different types of mechanical exposures at work, e.g. Deeb et al (1992). The work of Kilbom (1990, 1991) on the effect of isometric handgrip contractions on physiological factors for fatigue provides some strong indications that it may be possible to model physiological responses to work using a first-order system.…”

Forearm torque strengths and discomfort profiles in pronation and supination

“…Different muscles comprise different proportions of slow twitch and fast twitch fibres. Slow twitch fibres are more difficult to fatigue than muscles comprising predominately fast twitch fibres (Deeb et al 1992). Unfortunately there does not appear to be information in the literature regarding muscle composition for the forearm rotation muscles, with the exception of the biceps.…”