Controlled Frequency Breathing Reduces Inspiratory Muscle Fatigue

Controlled frequency breathing (CFB) is a common swim training modality involving holding one's breath for about 7 to 10 strokes before taking another breath. We sought to examine the effects of CFB training on reducing respiratory muscle fatigue. Competitive college swimmers were randomly divided into either the CFB group that breathed every 7 to 10 strokes, or a control group that breathed every 3-4 strokes. Twenty swimmers completed the study. The training intervention included 5-6 weeks (16 sessions) of 12x50-m repetitions with breathing 8-10 breaths per 50m (control group), or 2-3 breaths per 50-m (CFB group). Inspiratory muscle fatigue was defined as the decrease in maximal inspiratory mouth-pressure (MIP) between rest and 46s after a 200 yard free-style swimming race [115s (SD 7)]. Aerobic capacity, pulmonary diffusing capacity, and running economy were also measured pre and post-training. Pooled results demonstrated a 12% decrease in MIP at 46s post-race [-15 (SD 14) cm H2O, Effect size = -0.48, p < 0.01]. After four weeks of training, only the CFB group prevented a decline in MIP values pre to 46 s post-race [-2 (13) cm H2O, p> 0.05]. However, swimming performance, aerobic capacity, pulmonary diffusing capacity, and running economy did not improve (p> 0.05) post-training in either group. In conclusion, CFB training appears to prevent inspiratory muscle fatigue yet no difference was found in performance outcomes.