Maximum Weights of Handling Acceptable to People Aged 55–74 Years: Part II. Carrying

Abstract

Part I dealt with dynamic psychophysical strengths of the older population for manual lifting activities. Part II deals with dynamic psychophysical strengths of the older population for manual carrying activities (maximum acceptable weight of carry—MAWC). Subject population that participated in the manual carrying activities was the same that participated in manual lifting activities (ten males and ten females in each of the two age groups—55–74 years of age and 18–35 years of age). A questionnaire was used to identify carrying activities routinely performed in and around the home and workplace. Three of these activities were simulated in the 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 frequency of once and twice per minute and once every 5 minutes. As in the case of manual lifting, 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. The 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 either by age or frequency. None of the other responses (HR, VO₂, and CRRPE) for one-handed carrying and bag-carrying tasks were effected by either age or frequency. Although not directly compared, MAWC for all three activities were different.