Changes in athletes' brain network connections during isometric muscle contractions after sleep restriction

The quality of sleep influences brain function and motor performance negatively. This study established models for sleep restriction (SR) and muscle isometric contraction. By analyzing changes in brain network connectivity, key factors were identified that link alterations in brain network connections to decreased motor performance following SR.

Thirty-five participants underwent a randomized protocol comparing normal sleep (>7 h) and SR (< 4 h), followed by a movement task involving an isometric right biceps contraction at 30% MVC until exhaustion. Resting-state and task-related electroencephalography (EEG) and electromyography (EMG) signals were recorded. Preprocessed EEG data were analyzed using Brainstorm software for functional connectivity via phase locking value (PLV) across sensorimotor network (SMN), central executive network (CEN), default mode network (DMN), and salience network (SN). Gretna software computed connectivity strength and network efficiency in theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz) and gamma-1 (30-59 Hz) frequency bands. Principal component analysis identified key factors correlating with contraction duration.

SR significantly reduced the duration of sustained contraction to exhaustion of the biceps brachii muscle (p < 0.001). EMG analysis revealed a significant decrease in both the median frequency (MF) and average power frequency (MPF) values before exhaustion, indicating the onset of muscle fatigue. Brain network analysis results showed that during rest, connectivity in the theta, beta and gamma-1 was generally enhanced, particularly in CEN. Conversely, during the motor task, network connectivity strength in the theta, alpha and beta was generally decreased. Principal Component Analysis (PCA) further identified functional connections centered around DMN and network efficiency as representative neural markers. Correlation analysis indicated that SR altered the relationship between key brain network connections during the motor task and muscle performance. Under normal sleep conditions, the strength of connections within SMN and between SMN-DMN in the theta frequency band was negatively correlated with the duration of muscle contraction. However, following SR, this correlation weakened or reversed. The alteration in the SMN-DMN connection in the theta frequency band emerged as the most critical indicator for dissecting the impact of SR on motor performance.

SR significantly impaired the endurance performance of isometric contractions of the biceps brachii and specifically reconstructs the brain functional network: enhancing the connections of the theta, beta and gamma bands at rest. Under dynamic conditions, it weakens the connection of the theta, alpha and beta frequency bands, disrupting the integration of sensation and movement. The functional integration of the DMN and the connection mode of the SMN are the key neural markers that SR affects motor performance.