Low-Load x High-Load Resistance Exercise: Greater Cell Swelling After a Training Session

Abstract

Cell swelling caused by resistance training is proposed to provide an anabolic stimulus for muscle growth and it is believed that these effects are heightened with the use of low loads. The purpose of this study was to compare the acute effects of two volume-equated resistance training (RT) protocols, low-load (LL) versus high-load (HL), on elbow flexor muscles thickness, arm circumference, and blood lactate concentration in well-trained individuals. Eight resistance-trained males performed the following two RT protocols involving unilateral elbow flexion of the dominant arm: i) LL, four sets with 50% 1 repetition-maximum [1 RM] and ii) HL, ten sets with 85% 1 RM until failure, and equated volume. Pre- and post-session measurements included muscle thickness of the elbow flexors (biceps brachii and brachialis), upper arm circumference, and blood lactate concentration. Significant pre- to post-session increases were found in both protocols for muscle thickness (F (1, 28) = 11.74, p = 0.0019), and blood lactate (F (1, 28) = 35.55, p < 0.0001); no statistically significant differences were observed between conditions, however, the magnitude of increases favored LL. Significant between-condition differences favoring LL were observed for total repetitions (p = 0.007), time under tension (p = 0.007), and training density (p = 0.007). These results suggest that LL training promotes superior post-session increases in muscle thickness, indicating that RT protocols with longer times under tension and densities are beneficial when the goal is to promote acute cell swelling.

Keywords: Muscle hypertrophy; muscle turgescence; skeletal muscle; ultrasound imaging.

Figure 1

Muscle thickness values of elbow flexors (biceps brachii and brachialis) before (pre) and after (post) intervention for low-load and high-load, mean (± SD). Values expressed in millimeters (mm). * Significantly greater than the pre-training value (p < 0.05).

Figure 2

Arm circumference values of exercised arm before (pre) and after (post) intervention for low-load and high-load, mean (±SD). Values expressed in millimeters (mm).

Figure 3

Blood lactate concentration values before (pre) and after (post) intervention for low-load and high-load, mean (± SD). Values expressed in mmol/l. * Significantly greater than the pre-training value (p < 0.05).