Abstract
The purpose of this study was to assess whether the electromyographic (EMG) activity of the lower limb muscles - rectus femoris, vastus medialis, bicep femoris and gastrocnemius - during running is affected by different running environments and varied slope gradients. Data collected from this study would be useful for specific training programs adopted from different style runners. Ten male recreational runners participated in the current study. Each of the ten participants, was assessed in two different running conditions, treadmill running and over-ground running, which was consisted of a 20m distance running at a velocity of 11±1km/h at each of the following slope gradients -8%, -4%, 0%, 4%, 8% - in a randomized order. Findings revealed that when over-ground running EMG activity of the lower limb muscles was 16.54% higher compared to treadmill running. Treadmill running is characterized by reduced metabolic cost, which is related to lower muscle activation requirements. Varied slope gradients found to affect muscle activation. During uphill running, lower limb muscle activation was significantly higher compared to level and downhill running, independently of running environment. However, running at negative slope gradients was associated with significantly greater muscle activation compared to level running, only on the treadmill condition.
Highlights
The physical activity of running is a key element in most conditioning programs
The purpose of this study was to assess whether the electromyographic (EMG) activity of the lower limb muscles during running is affected by a) different running environments and b) varied slope gradients
Downhill running is characterized by greater knee flexion angle which is associated with an increased vertical displacement of the centre of mass and an increased maximal vertical force value [3]
Summary
The physical activity of running is a key element in most conditioning programs. Running at different slope gradients (positive and negative) and varied environments (overground and treadmill running) is a commonly used method in training programs for distance runners.Inclined support surfaces affect the control of movement in terms of the maintenance of an upright posture, the foot strike patterns and the related centre of pressure in anteriorposterior direction during stance, and the corresponding muscle activity. Uphill running is characterized by a reduction in vertical displacement of the centre of mass with a simultaneous decrease in maximal vertical force components, compared to level and downhill running. The proportion of contact time during the step cycle was grater at increased gradients (from +3% to +11%) [3, 4, 7], while flight time and American Journal of Sports Science 2019; 7(1): 20-25 step length were decreased [4, 5]. These changes in spatiotemporal parameters caused by varied gradients interact with the work performed by muscle groups during running. Greater activation of the muscle groups surrounding the hip joint (hamstrings and iliopsoas) and the muscles surrounding the knee joint (vastii muscles and rectus femoris) was observed during uphill running at a high speed (5m/sec), compared to level running [9]
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