Muscle Oxygenation and Autonomic Recovery After Repeated Sprint in Competitive Soccer Players

This study uses a single-group repeated-measures design to investigate muscle oxygenation, cardiac autonomic recovery, and neuromuscular performance responses following repeated sprint exercise in competitive male soccer players.

A total of 48 licensed male soccer players participate in the study. Participants regularly train and compete in soccer and have at least four years of soccer training experience.

During the measurement session, demographic and anthropometric characteristics are recorded first. Baseline measurements include heart rate variability, muscle oxygen saturation, blood lactate concentration, and countermovement jump performance. After a standardized 10-minute warm-up, participants complete an 8 × 30 m repeated sprint protocol. Each sprint is performed with maximal effort, and a 25-second active/light jogging recovery period is provided between sprints. Sprint times are recorded using an electronic timing gate system.

Muscle oxygenation is continuously assessed using portable near-infrared spectroscopy sensors placed on the vastus lateralis and biceps femoris muscles of the dominant leg. The evaluated muscle oxygenation variables include baseline muscle oxygen saturation, minimum muscle oxygen saturation, desaturation difference, 30-second reoxygenation muscle oxygen saturation, and reoxygenation rate.

Cardiac autonomic recovery is evaluated using heart rate variability derived from R-R interval recordings obtained with a Polar H10 chest strap. Five-minute HRV recordings are obtained at baseline, 5 minutes after the repeated sprint protocol, 30 minutes after the protocol, and 24 hours after the protocol. RMSSD and SDNN are used as the primary time-domain HRV parameters.

Neuromuscular performance is evaluated using countermovement jump height before the repeated sprint protocol, 10 minutes after the protocol, and 24 hours after the protocol. Blood lactate concentration is measured before the protocol and at 3 minutes after the protocol. Rating of perceived exertion is recorded after completion of the sprint protocol using the Borg CR10 scale.

The study is designed to characterize the time course of recovery following repeated sprint exercise and to examine relationships among sprint performance, muscle oxygenation, cardiac autonomic recovery, and neuromuscular performance. Because the study uses a single-group design without a control group, the findings are interpreted as recovery-related associations rather than evidence of causal effects.

Inclusion criteria

• Licensed male competitive soccer player
• Age between 18 and 26 years
• Regularly participating in soccer training within a club
• Actively participating in official competitions
• At least 4 years of soccer training experience
• Physically able to complete the repeated sprint protocol
• No acute injury or illness on the measurement day
• Voluntary agreement to participate and provision of written informed consent

Exclusion criteria

• Acute lower-extremity injury
• Acute illness on the measurement day
• Inability to complete the repeated sprint protocol
• Missing data at any required measurement time point
• Failure to complete the 24-hour follow-up measurements