Academic journal article Research Quarterly for Exercise and Sport

Characteristics of the Vertical Ground Reaction Force Component Prior to Gait Transition. (Biomechanics)

Academic journal article Research Quarterly for Exercise and Sport

Characteristics of the Vertical Ground Reaction Force Component Prior to Gait Transition. (Biomechanics)

Article excerpt

The purpose of the study was to examine the vertical ground reaction force component when approaching the gait transition point from either a walk-to-run or run-to-walk perspective. The vertical ground reaction forces (VGRF) of five steps before gait transitions for both walk-to-run and run-to-walk were collected on a motor driven treadmill with embedded force plates. Transition specific characteristics of the VGRF were observed for both types of gait transition. Running peak force and time to peak force reduced dramatically in a quadratic fashion as approaching to the run-to-walk transition. The walking VGRF first peak increased linearly, and the second peak decreased quadratically prior to walk-to-run transition. Walking VGRF appearing to be more sensitive to acceleration than the running VGRF.

Key words: biomechanics, locomotion, run, walk

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People walk at lower speeds and run at greater speeds. Within each type of locomotion, minimal energetic cost has been suggested as the primary factor for selecting preferred speeds among either humans or animals (e.g., Holt, Hamill, & Andres, 1991, for human walking; Hoyt & Taylor, 1981, for horse walking and trotting). Naturally, energetic cost has been proposed as a trigger for gait transition, as walking affords a lower energy cost at lower speeds, while running affords a lower energy cost at higher speeds (Margaria, Cerretelli, Aghemo, & Sassi, 1963). Hreljac (1993) observed differences between energetically optimal transition speed and preferred transition speed between human walking and running. Subsequently, Hreljac (1995) observed that the maximum ankle joint acceleration changed dramatically during walk-to-run transition and a kinematic trigger was suggested. Using an equine model, Farley and Taylor (1991) proposed that lower extremity muscle stress could trigger the trot-to-gallop transition with i ncreased locomotion speed. All the proposed gait transition mechanisms can only provide a partial explanation for the nature of the gait transition. Based on dynamic systems theory, Diedrich and Warren (1995) examined the variability of the discrete relative phases, as collective measure to reflect the system's behavior, during gait transition. Increased variability observed as approaching to gait transition. The study of ground reaction forces, the only external contact force during locomotion and interpreted as comprehensive reflection of the locomotory system, may enhance our understanding regarding the mechanism of gait transition.

Hamill, Bates, and Knutzen (1984) conducted comparisons of ground reaction forces during walking (1.36 m/s) and running (4.87 m/s), and reported significant differences between the two gait patterns. To differentiate between the influence of speed and the influence of gait type on locomotion ground reaction forces, Nilsson and Thorstensson (1989) investigated walking and running ground reaction forces at different locomotion speeds. The participants were required to walk at five different speeds, ranging from 1.0 to 3.6 m/s, and run at seven speeds, ranging from 1.5 to 6.0 m/s. The locomotion speed was held constant during each condition. The authors observed that locomotion speed influenced the ground reaction force patterns of walking and running.

Due to technological constraints, the aforementioned researchers did not provide information on how the ground reaction forces changed during the steps preceding the gait transitions. Both Hamill et al. (1984) and Nilsson and Thorstensson (1989) collected data using a single-force platform fixed Within an overground walkway. As a result, the ground reaction forces were only collected with constant velocities. Although unable to determine shear forces, a treadmill with an imbedded force platform provides a means with which to monitor the vertical ground reaction force continuously (White, Yack, Tucker, & Lin, 1998). The purpose of the study was to examine the vertical ground

reaction force component when approaching the gait transition point from either a walk-to-run or run-to-walk perspective. …

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