Cluster Training With Blood Flow Restriction in Competitive 200-m Freestyle Swimmers (BFR-CLUSTER-SW)

Blood flow restriction (BFR) training is a training method in which pneumatic cuffs are applied proximally to the limbs to partially restrict vascular flow during exercise. Cluster training divides traditional exercise sets into smaller clusters of repetitions separated by short intra-set recovery periods. Combining these two approaches may increase the physiological stimulus of training while allowing repeated high-quality exercise efforts.

This controlled, non-randomized matched-intervention study included 20 competitive 200-m freestyle swimmers. Participants were matched according to baseline 200-m freestyle performance, sex, and standing long jump distance and were assigned to one of two groups. The experimental group completed cluster training combined with BFR, whereas the control group completed cluster training without BFR.

The training intervention lasted 8 weeks and consisted of five 90-minute training sessions per week. Sessions included a standardized warm-up, a main training component, and a cool-down. Overall cardiovascular training intensity was prescribed relative to individual maximal heart rate, and cluster-based resistance exercises incorporated short intra-set recovery intervals.

BFR was applied only in the experimental group during selected dry-land cluster exercises using pneumatic cuffs positioned proximally on the upper arms and thighs. The cuffs remained inflated during exercise execution and short intra-set recovery periods and were deflated during the main inter-set recovery periods.

The primary outcome was change in 200-m freestyle performance time from baseline to the end of the 8-week intervention. Secondary outcomes included serum FGF-2 and VEGF-A concentrations, standing long jump distance, mean 50-m split time during a maximal 150-m swimming test, and performance in a cadence-controlled Burpee test. Blood samples were collected under standardized resting conditions to assess serum FGF-2 and VEGF-A concentrations.

The main objective was to determine whether the addition of BFR to cluster training was associated with greater improvements in swimming performance, selected physical-performance outcomes, and serum angiogenesis-related biomarkers compared with cluster training alone.