This uncorrected galley proof reports an 8‑week randomized controlled trial investigating how three cluster‑training (CL) protocols, differing in intra‑set rest intervals (RIntra) and repetition‑block sizes (BK), affect lower‑limb fat‑free mass (FFM), squat strength, and countermovement jump (CMJ) performance in 29 resistance‑trained men who maintained a high‑protein diet. Participants were allocated to (1) CL1: 20 s RIntra, 3 RM blocks (n=8), (2) CL2: 40 s RIntra, 3 RM blocks (n=7), (3) CL3: 20 s RIntra, 6 RM blocks (n=7), or (4) control (CG, n=7). All groups trained twice weekly on lower‑limb exercises (squat, deadlift, leg press) for 8 weeks, with volume load equated across CL groups. Body composition was measured by DXA, squat 1RM was assessed with a Smith machine, and CMJ height was recorded on a jump mat. Results showed significant increases in lower‑limb FFM for all CL groups (CL1 + 0.9 kg, CL2 + 0.6 kg, CL3 + 0.6 kg; p ≤ 0.011) but not for CG. Squat strength improved markedly in CL1 (+14.5 kg, ES 0.80) and moderately in CL2 (+10.1 kg, ES 0.60) and CL3 (+9.5 kg, ES 0.45); CG showed a non‑significant trend (+9.0 kg, ES 0.55). CMJ performance did not change significantly in any group. The authors conclude that a ~20 s intra‑set rest with 3 RM blocks is sufficient to elicit meaningful hypertrophic and strength adaptations, while longer rests confer no additional benefit. Practical recommendations emphasize using short intra‑set rests for efficiency, monitoring fatigue, and suggest future work on varying block sizes and perceived‑exertion‑based training.
Topics
Randomized Controlled Trial Design with Four Distinct Training Arms
A parallel‑group RCT allocated 29 male participants to three cluster‑training protocols varying intra‑set rest (20 s vs 40 s) and block repetitions (3 RM vs 6 RM), plus a non‑supervised control group.
Cluster Training Protocols: Intra‑Set Rest and Repetition Block Configurations
Detailed description of CL1 (20 s RIntra, 3 RM blocks), CL2 (40 s RIntra, 3 RM blocks), CL3 (20 s RIntra, 6 RM blocks), including exercise selection, set/rep scheme, volume‑load matching, and supervision.