Uphill Race Walking At Iso-Efficiency Speed

ABSTRACT: The aim of this study was to investigate the effects of gradients (0, 2 and 7%) on biomechanical parameters during race walking (RW) at Iso-Efficiency Speed (IES). During the experiment twelve high level athletes performed at IES on different slopes. The parameters studied were: surface muscular activity (sEMG) of five muscles of the leg using Muscle Lab; kinematic parameters were collected using a high speed camera (210 Hz) analyzed with Dartfish 5.5Pro and heart rate was monitored with a Cardio Polar. The results showed step length (SL), step frequency (SF) and internal work (WINT) decreased with increased treadmill gradient: SL= [(0-2%= 3.48%, p= 0.158), (0-7%= 12.17%, p< 0.001)]; SF= [(0-2%= 2.38%, p= 0.173), (0-7%= 6.07%, p< 0.01)]; WINT= [(0-2%= 8.34%, p< 0.001), (0-7%= 22.81%, p< 0.0001)]. Conversely contact time (CT) and heart rate (HR) increased less significantly with the increased gradients: CT= [(0-2%= 2.46%, p= 0.198), (0-7%= 6.56%, p< 0.01)]; HR= [(0-2%= 0.62%, p= 0.652), (0-7%= 3.25%, p< 0.05)]. The knee angle (KE) increased, while ankle angle (AK) and hip angle (HP) decreased with the increased gradients. AK= [(0-2%= 1.69%, p< 0.001), (0-7%= 1.13%, p< 0.01)]; HP= [(0-2%= 0.22%, p< 0.03), (0-7%= 0.16%, p= 0.456)]; KE= [(0-2%= 1.01%, p< 0.001), (0-7%= 1.60%, p< 0.001)]. EMG significantly decreased with the increased gradients in the: tibialis anterior [(0-2%= 22.49%, p< 0.0001), (0-7%= 41.18%, p< 0.0001)] and rectus femoris [(0-2%= 15.35%, p< 0.0001), (0-7%= 29.13%, p< 0.0001]. In contrast, EMG activity was significantly increased in the vastus lateralis [(0-2%= 22.95%, p< 0.0001), (0-7%= 31.15%, p< 0.0001)], gastrocnemius medialis [(0-2%= 21.40%, p< 0.001), (0-7%= 48.37%, p< 0.0001] and biceps femoris [(0-2%= 190.78%, p< 0.0001), (0-7%= 201.37%, p< 0.0001]. The results indicate that increasing the gradient to 2% did not elicit an increased heart rate in race walkers, however at a 7% gradient greater muscle activity was required.