Effect Of Strength And Body Composition On Upper- And Lower-body Work Capacity In Adult Men

Abstract

Heavy resistance training may enhance low-intensity work capacity (load x repetitions) but reduce high-intensity work capacity in both competitive and recreational individuals. However, most research has focused on upper-body work capacity with little information available for lower-body work capacity. PURPOSE: The purpose of this study was to assess the effects of strength level and body composition on upper- and lower-body work capacity in adult men. METHODS: From 295 adult men, low-strength (LS, n = 72) and high-strength (HS, n = 66) samples were selected based on one-repetition maximum (1RM) bench press (BP) and leg strength (LP). Group limits were determined using the lower and upper 40% of the sample. Work capacity was determined from repetition weight (RepWt = 79.5 ± 2.5% of 1RM) multiplied by maximum repetitions-to-fatigue (RTF). Body composition was measured using DXA. RESULTS: HS group was significantly greater in body mass and lean mass than LS, but not different in age, height, fat mass, or %fat. LS and HS groups were not significantly different in the RTF for either BP (8.7 ± 3.1 vs 8.3 ± 1.9) or LP (15.6 ± 7.6 vs 17.0 ± 6.3), which made the ratio of LP-RTF to BP-RTF nonsignificantly different between the LS (2.0 ± 1.0) and HS (2.2 ± 0.9) groups. RTF in the BP and LP were significantly correlated in the LS group (r = 0.31) but not in the HS group (r = 0.11). Significantly greater RepWt in the HS group resulted in greater (p<0.001) absolute and relative work capacities for both BP (818 ± 207 and 9.1 ± 2.6) and LP (4,354 ± 2,086 and 48.4 ± 23.2) vs. the LS group (522 ± 183 and 6.8 ± 2.3; 1,856 ± 1,029 and 24.2 ± 13.9). RTF explained a larger percent contribution explaining BP and LP work capacities in the LS group (79% and 85%, respectively) than did RepWt (21% and 15%, respectively). In the HS group, RTF (81%) contributed more than RepWt (19%) to explaining BP work capacity, while the two components were more similar in explaining LP work capacity (60% and 40%, respectively). CONCLUSION: When work is determined using the same %1RM load, LS and HS individuals produce equivalent muscular endurance values when evaluated by RTF, but HS individuals have greater work capacity when the criterion is determined as load × RTF. Controlling for body composition among strength groups does not eliminate the difference in work capacity.