Ikezoe, T, Kobayashi, T, Nakamura, M, and Ichihashi, N. Effects of low-load, higher-repetition vs. high-load, lower-repetition resistance training not performed to failure on muscle strength, mass, and echo intensity in healthy young men: A time-course study. J Strength Cond Res 34(12): 3439–3445, 2020—The aim of this study was to compare the effects of low-load, higher-repetition training (LLHR) with those of high-load, lower-repetition training (HLLR) on muscle strength, mass, and echo intensity in healthy young men. Fifteen healthy men (age, 23.1 ± 2.6 years) were randomly assigned to 1 of the 2 groups: LLHR or HLLR group. Resistance training on knee extensor muscles was performed 3 days per week for 8 weeks. One repetition maximum (1RM) strength, maximum isometric strength, muscle thickness, and muscle echo intensity on ultrasonography of the rectus femoris muscle were assessed every 2 weeks. Analysis of variance showed no significant group × time interaction, and only a significant main effect of time was observed for all variables. The 8-week resistance training increased 1RM, maximum isometric muscle strength, and muscle thickness by 36.2–40.9%, 24.0–25.5%, and 11.3–20.4%, respectively, whereas it decreased echo intensity by 8.05–16.3%. Significant improvements in muscle strength, thickness, and echo intensity were observed at weeks 2, 4, and 8, respectively. The lack of difference in time-course changes between LLHR and HLLR programs suggests that low-load training can exert similar effects on muscle mass and characteristics as high-load training by increasing the number of repetitions, even when not performed to failure.