Respiratory muscles play a fundamental role in sports performance. Fatigue of these muscles induces changes in maximal inspiratory pressure and autonomic nervous system activity, thereby compromising the athlete's recovery process. The primary aim of this study is to evaluate the specific effects of different inspiratory muscle activation modalities on post-exercise recovery in professional male football players. The study seeks to determine which of the three modalities-bilateral phrenic nerve electrical stimulation, a threshold loading device protocol, or inactivity-provides greater benefits for recovery. The effectiveness of these interventions will be assessed using two key outcome variables: maximal inspiratory pressure (MIP) and heart rate variability (HRV). This study is designed as a randomized clinical trial (RCT) in which participants will be allocated into three intervention groups: a bilateral phrenic nerve electrical stimulation group (EG1), in which involuntary diaphragmatic contractions will be induced using an electrotherapy device with current applied to the phrenic nerves; a threshold device group (EG2), in which participants will perform breathing against submaximal inspiratory loads equivalent to 40% of their MIP; and a control group (CG), which will remain seated for a period equivalent to the duration of the other interventions. Group allocation will be ensured through randomization using Microsoft Excel. Regarding statistical analysis, data normality will be assessed using the Shapiro-Wilk test. Comparisons of quantitative variables will be performed using Student's t test when normality assumptions are met, or the Mann-Whitney U test otherwise. A p value \< 0.05 will be considered statistically significant.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
30
Phrenic nerve stimulation using low-frequency symmetric biphasic current
Deep inspirations against submaximal inspiratory load
Hear rate variability
HRV will be assessed using a heart rate monitor (Polar H10; Polar Electro Oy, Kempele, Finland) with participants in the supine position in a quiet room (\~25 °C, dim lighting). Cardiac signals will be recorded for 3 minutes via a chest strap. Participants will avoid caffeine, alcohol, tobacco, and intense exercise for 12 h prior, and refrain from speaking or voluntary movements during recording. Analysis will be performed with Kubios HRV 3.1.0 (University of Kuopio, Finland), examining LF/HF ratio, LF (0.04-0.15 Hz) and HF (0.15-0.40 Hz) power in normalized units, SDNN, and RMSSD.
Time frame: Pre-match 24 hours before (baseline); Post-match 24 hours (pre-intervention); Immediately post-intervention; 15 minutes post-intervention; 30 minutes post-intervention
Maximal Inspiratory Pressure
Maximal inspiratory pressure (MIP) will be assessed with participants in a seated position using the Breathcare MIP/MEP device (Big Breathe®, GH Innotek Co., Ltd., Busan, Republic of Korea). The examiner will demonstrate the maneuver prior to its execution. To ensure proper airflow through the mouth, the nostrils will be occluded. Participants will perform up to six maneuvers per attempt, with a 1-minute rest between each. The most consistent and reproducible result from three attempts, with a variation of less than 5%, will be selected for analysis.
Time frame: Pre-match 24 hours before (baseline); Post-match 24 hours (pre-intervention); Immediately post-intervention; 15 minutes post-intervention; 30 minutes post-intervention
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