Assessment of Muscular Fatigue with Electromyography on Lower Back and Leg Muscles during Continuous Uphill and Downhill Load Carriage Task

Abstract

Soldiers of Indian Army need to carry moderate to heavy load in complex terrain conditions as their routine activity, which may prove to be highly tiring for leg and back muscles. Soldiers’ regular movement at hilly area was simulated in a study consisting of a continuous uphill (UH) and downhill (DH) load carriage task to monitor state of fatigue at back and lower limb muscles. Twelve Indian soldiers walked at a fixed speed on five UH and five DH gradients with three loads (0, 10.7 kg and 21.4 kg). Electromyographic (EMG) recording was carried out throughout the experimentation on four groups of muscles- left and right Erector spinae (ESR and ESL), Vastus medialis (VMR and VML), Gastrocnemius medialis (GMR and GML), and Soleus (SOR and SOL) muscles. Median frequency (MDF) responses of tested muscles were derived from raw (EMG) data. Higher level of muscle fatigue was observed at highest UH inclination as the MDF response in GMR, GML and VMR was lowest at this point. The MDF response were found to be lower at DH gradients as the physical demand of that stage is less than the UH gradients.