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To compare the acute responses to different set configurations (cluster [CLU] vs. traditional [TRA]) under distinct blood flow conditions (free vs. restricted) in full-squat (SQ). Twenty resistance-trained males performed 4 protocols that differed in the set configuration (TRA: continuous repetitions; vs. CLU: 30 seconds of rest every 2 repetitions) and in the blood flow condition (FF: free-flow; vs. blood flow restriction [BFR]: 50% of arterial occlusion pressure). The relative intensity (60% 1RM), volume (3 sets of 8 repetitions), and resting time (2 minutes) were equated. Mean propulsive force (MPF), velocity (MPV) and power (MPP), and electromyography (EMG) parameters were recorded during each repetition. Ten-siomyography (TMG), blood lactate, countermovement jump (CMJ) height, maximal voluntary isometric contraction, in SQ, and movement velocity against the load that elicited a 1 m⋅s-1 velocity at baseline (V1-load) in SQ were assessed at pre- and post-exercise. The CLU protocols allowed a better maintenance of MPF, MPV, MPP, and EMG median frequency during the exercise compared to TRA (clu-time interaction, p < 0.05). The TRA protocols experienced greater impairments post-exercise in TMG- and EMG-derived variables (clu-time interaction, p < 0.05) and SQ and CMJ performance (clu-time interaction, p = 0.08 andp < 0.05, respectively), as well as higher blood lactate concentrations (clu-time interaction, p < 0.001) than CLU. Moreover, BFR displayed decreases in TMG variables (bfr-time interaction, p < 0.01), but BFR-CLU resulted in the greatest reduction in twitch contraction time (p < 0.001). Cluster sets reduced fatigue during and after the training session and BFR exacerbated impairments in muscle mechanical properties; however, the combination of both could improve contraction speed after exercise. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: This study compared the effects of four different resistance training (RT) programs that differed in the set configuration (cluster vs. traditional) and the blood flow condition [free-flow (FF) vs. blood flow restriction (BFR)] on strength, neuromuscular and hypertrophic adaptations.Methods: Forty-two resistance-trained males were randomly assigned into four protocols that differed in the set configuration (TRA: without rest between repetitions vs. CLU: 30 s rest every 2 repetitions) and in the blood flow condition [FF vs. BFR (50% of arterial occlusion pressure)]. Subjects followed an 8-week RT program, twice per week, with similar intensity (55%-65% 1RM), sets (3), repetitions per set (10-6), and resting time (2 minutes) in the full-squat (SQ) exercise. Before and after the RT program, they were evaluated for: 1) muscle size of the vastus lateralis; 2) vertical jump; 3) maximal isometric contraction; 4) progressive loading test; and 5) fatigue test.Results: BFR-TRA and FF-CLU induced greater increases in 1RM, and velocity against submaximal loads than FF-TRA and BFR-CLU (BFR × time and CLU × time interactions, p = 0.02). The TRA protocols showed greater increases in maximal isometric force than CLU (CLU × time interaction, p = 0.03). BFR did not enhance jump performance unlike the FF protocols (p < 0.01). The TRA protocols induced greater hypertrophy in the distal region of the vastus lateralis than CLU protocols (CLU × time interaction, p = 0.04), with BFR-TRA producing the greatest gains in all vastus lateralis sections.Conclusions: The different combinations of set configurations and blood flow conditions resulted in highly specific adaptations that illustrate the potential of adaptation for each protocol. The divergent underlying mechanisms of CLU and BFR methodologies may offset each other when combined., Competing Interests: Conflict of Interest and Funding Source: This study has no conflicts of interest to declare. This study was funded by the Spanish Ministry of Science and Innovation (AEI/10.13039/501100011033; grant reference PID2020-117915RA-I00). Daniel Boullosa was supported by Grant RYC2021-031098-I funded by MCIN/AEI/10.13039/501100011033, by “European Union NextGenerationEU/PRTR”, and by a productivity research grant (PQ1D) from CNPq (Brazil). Mathias Wernbom gratefully acknowledges support by The Sports Research Network of the Swedish Olympic Committee., (Copyright © 2024 by the American College of Sports Medicine.)