Aging and Performance in Manual Carrying Activities: An Experimental Investigation

Abstract

This paper presents a research study on the dynamic psychophysical strengths of the older population for manual carrying activities (maximum acceptable weight of carry - MAWC). 10 males and 10 females in each of two age groups — 55 to 74 years, and 18 to 35 years, participated in the manual carrying activities. A questionnaire was used to identify carrying activities routinely performed in and around the home and workplace. Three of these activities were simulated in laboratory settings, and included a two-handed carrying task, a one-handed carrying task, and bag carrying. All carrying activities were performed over a carrying distance of 6 m, and carrying frequencies of once and twice per minute and once every 5 minutes. The psychophysical approach was used to determine MAWC. Heart rate (HR), oxygen uptake (VO₂), and category-ratio ratings of perceived exertion (CRRPE) at the MAWC were also recorded. Results indicated that MAWC for two-handed tasks was significantly influenced by age for males - younger males carried 26% more weight than older males. Males, even though carrying less weight in two hands, were subjected to higher physiological burden (elevated heart rate). Females performing two-handed carrying tasks, on the other hand, exhibited no age effect. MAWC for males and females for one-handed carrying tasks and bag carrying were not affected by age or frequency. None of the other responses (HR, VO₂, and CRRPE) for one-handed carrying and bag carrying tasks were affected by either age or frequency. Although not directly compared, MAWC for all three activities were different.