Abstract

Inspiratory muscle training (IMT) is widely recognized as an effective strategy to improve cardiorespiratory efficiency, increase functional capacity, and modulate the autonomic nervous system in both healthy individuals and those with chronic conditions. In the field of sports, IMT has gained growing interest in its potential to optimize physical performance and enhance recovery following intense physical efforts. Therefore, this study aimed to evaluate the effects of a short IMT protocol on relevant physiological parameters in amateur runners. Forty recreational runners (20 men and 20 women; 35.33 +/- 6.13 years; 69.77 +/- 11.02 kg; 168.70 +/- 8.86 cm; 24.43 +/- 2.55 kg/m(2)) were randomly assigned to an intervention group (n = 20) or a control group (n = 20). The intervention consisted of 5 minutes of daily training at 50% maximal inspiratory pressure (MIP) for 10 consecutive days. Maximal Oxygen Consumption (VO(2)max), Second Ventilatory Threshold (VT2), MIP, and heart rate variability (HRV), specifically the root mean square of successive differences (RMSSD), were assessed. Baseline characteristics did not differ significantly between groups, except for age (p = 0.012). Significant time group interactions were found for VO(2)max, VT2, RMSSD, and MIP (all p < 0.001). Compared with the control group, the IMT group showed greater improvements in VO(2)max (+2.87 ml/kg/min ; d = 0.59), VT2 (+2.61 ml/kg/min; d = 0.68), RMSSD (+5.69 ms; d = 0.58), and MIP (+15.48 cmH(2)O; d = 1.71). Increases in MIP correlated positively with changes in VO(2)max (rho = 0.74), VT2 (rho = 0.77), and RMSSD (rho = 0.71; all p < 0.001). These findings support the efficacy of short-duration IMT as a complementary tool to improve cardiorespiratory performance and autonomic modulation in recreational athletes, without requiring long periods of intervention.