The Interaction of Treadmill Type and Incline Slope on Biomechanics and Muscle Activation During Human Locomotion

To investigate the effects of differing treadmills on impact acceleration and muscle activation.

15 males and 7 females (27.8 ± 7.7yrs), engaged in two sessions of high-incline walking (HIW), and low-incline jogging (LIJ) on different deck systems (cushioned) treadmills (TM1 and TM2). Sessions lasted 5-minutes, and participants maintained a self-selected pace matched for each session. EMG markers were placed over the Tibialis Anterior (TA), Soleus (SOL), Lateral Gastrocnemius (LG), Biceps Femoris (BF), Gluteus Maximus (GM), Anterior Deltoid (AD), Vastus Lateralis (VL), and the Erector Spinae (ES). Trident Inertial Measurement Units (IMU) were attached to the foot and sacrum. EMG activity, impact accelerations, heart rate, and RPE were collected at the 4-minute 30-seconds mark.

Peak EMG was higher for LG (p = 0.005), SOL (p = 0.010), and BF (p < 0.001) on TM1 compared to TM2, while AD exhibited lower peak activation during HIW compared to LIJ on TM2 (p = 0.010). The integral EMG activity increased for AD, ES, VL, SOL, LG, and GM only during HIW for both TM1 and TM2. However, only integral EMG activation of BF and LG differed between TM1 and TM2 during HIW. Foot and sacrum resultant acceleration was notably lower during HIW compared to LIJ on both TM1 and TM2. HR was significantly higher on TM1 (171.2 ± 24.8bpm) compared to TM2 (164.62 ± 23.7 bpm, p < .05) during HIW (p < .001), and RPE also differed between TM1 (13.96 ± 1.96) and TM2 (13.09 ± 1.97) during HIW (p < .05).

At the same speed (correspond to an RPE of 11) and grade, treadmill design may impact peak and integral muscle EMG patterns, RPE, and HR responses.