Measurement of Low Back Muscle Fatigue and Recovery Time During and After Isometric Endurance Test

The aim of this study was to examine the relationship between myoelectrical manifestation and muscle oxygenation level by surface electromyography (EMG) and Near-infrared spectroscopy (NIRS), respectively. As well as the recovery time based on tissue oxygenation index (TOI) after isometric exercise on erector spinae muscle (ESM). Eleven healthy females (age = 18.8 +/- 0.7 years, height = 1.59 +/- 0.0 m, BMI = 20.1 +/- 1.8; mean +/- SD) performed an isometric back trunk extension (Biering-Sorensen Muscle Endurance test-BSME) of their 40 % of their mean maximal voluntary contraction (MVC) until exhaustion. Muscle oxygenation decreased immediately at the beginning of exercise. Maximal deoxygenation occurred at 100 % BSME time, and decreased about 15 % from the resting value. A strong correlation between frequency content of the EMG signal and TOI was established, r = 0.78 (right) and r = 0.90 (left). These findings suggest that the fatigue resulting from sustained isometric exercise are related to a decrease in oxygenation level following by the increasing time of contraction of the ESM.