Electromyographic Activity During Nordic Hamstring Exercise in Male Soccer Players

Participants complete a single standardized assessment session. Baseline sociodemographic and anthropometric characteristics are recorded before testing. The Nordic Hamstring Exercise is performed from a kneeling position while an evaluator or training partner stabilizes the participant's ankles and lower legs. The participant maintains the trunk and thighs aligned and controls the forward descent primarily through eccentric hamstring action. The descent is paced at approximately 3 seconds. The hands and arms are used to arrest the fall and assist the return to the initial position in order to minimize concentric loading.

Six valid maximal-effort Nordic Hamstring Exercise repetitions are recorded, with recovery between repetitions. Surface electromyographic activity is collected throughout the assessment from the biceps femoris and gluteus maximus.

Surface electromyography is recorded using the mDurance® system (mDurance Solutions SL, Granada, Spain), based on a portable Shimmer3 EMG unit with two surface EMG channels, a sampling frequency of 1024 Hz, 24-bit signal resolution, and an overall amplification range of 100-10,000 V/V. The recorded signals are processed using the mDurance methodology, including a fourth-order Butterworth band-pass filter with cut-off frequencies of 20-450 Hz and root mean square smoothing with a 0.025-second window and 0.0125-second overlap. Skin preparation and electrode placement follow standardized surface electromyography procedures.

Electromyographic amplitude is normalized to a maximal voluntary isometric contraction reference and expressed as a percentage of MVIC (%MVIC). The main variables are the peak normalized RMS amplitude of the biceps femoris and gluteus maximus during the six repetitions, together with pre-exercise and immediately post-exercise normalized activation. Comparisons are performed between 11-a-side soccer and futsal players.

Inclusion criteria

• Male soccer or futsal player aged 18 years or older.
• Regular participation in 11-a-side soccer or futsal.
• Previous physician-diagnosed hamstring muscle injury classified as type 2b according to the Munich Consensus during the previous 12 months, but not within the month preceding assessment.
• Absence of current lower-limb pain or active musculoskeletal injury at the time of assessment.
• Ability to understand and perform the study procedures.
• Voluntary agreement to participate and provision of written informed consent.

Exclusion criteria

• Participation in an organized hamstring stretching program that could interfere with the assessment.
• Current pain, musculoskeletal injury, or recent surgery involving the lumbar spine, abdominal region, or lower limbs.
• Evidence or history of a neurological disorder affecting lower-limb function.
• Skin lesions or dermatological conditions preventing placement of surface electromyography electrodes.
• Moderate-to-vigorous physical activity within the 72 hours preceding testing.