Internal Loads, but Not External Loads and Fatigue, Are Similar in Young and Middle-Aged Resistance-Trained Males during High Volume Squatting Exercise †

Little is known about the internal and external loads experienced during resistance exercise, or the subsequent fatigue-related response, across different age groups. This study compared the internal (heart rate, OMNI ratings of perceived exertion (RPE), session RPE) and external loads (peak velocity and power and volume load) during high volume squatting exercise (10 × 10 at 60% one-repetition maximum (1RM)) and the fatigue-related response (maximal voluntary contraction (MVC), voluntary activation (VA), resting doublet force, peak power, and blood lactate) in young (n = 9; age 22.3 ± 1.7 years) and middle-aged (n = 9; age 39.9 ± 6.2 years) resistance-trained males. All internal load variables and peak velocity illustrated unclear differences between groups during exercise. Peak power and volume load were likely higher in the young group compared to their middle-aged counterparts. The unclear differences in MVC, VA and blood lactate between groups after exercise were accompanied by very likely greater decrements in resting doublet force and peak power at 20 and 80% 1RM in the middle-aged group compared to the young group. These data indicate that internal load is not different between young and middle-aged resistance-trained males, though certain external load measures and the fatigue response are.