Why do we transition from walking to running? Energy cost and lower leg muscle activity before and after gait transition under body weight support

Abstract

BackgroundMinimization of the energetic cost of transport (CoT) has been suggested for the walk-run transition in human locomotion. More recent literature argues that lower leg muscle activities are the potential triggers of the walk-run transition. We examined both metabolic and muscular aspects for explaining walk-run transition under body weight support (BWS; supported 30% of body weight) and normal walking (NW), because the BWS can reduce both leg muscle activity and metabolic rate.MethodsThirteen healthy young males participated in this study. The energetically optimal transition speed (EOTS) was determined as the intersection between linear CoT and speed relationship in running and quadratic CoT-speed relationship in walking under BWS and NW conditions. Preferred transition speed (PTS) was determined during constant acceleration protocol (velocity ramp protocol at 0.00463 m·s−2 = 1 km·h−1 per min) starting from 1.11 m·s−1. Muscle activities and mean power frequency (MPF) were measured using electromyography of the primary ankle dorsiflexor (tibialis anterior; TA) and synergetic plantar flexors (calf muscles including soleus) before and after the walk-run transition.ResultsThe EOTS was significantly faster than the PTS under both conditions, and both were faster under BWS than in NW. In both conditions, MPF decreased after the walk-run transition in the dorsiflexor and the combined plantar flexor activities, especially the soleus.DiscussionThe walk-run transition is not triggered solely by the minimization of whole-body energy expenditure. Walk-run transition is associated with reduced TA and soleus activities with evidence of greater slow twitch fiber recruitment, perhaps to avoid early onset of localized muscle fatigue.

Economical and preferred walking speed using body weight support apparatus with a spring-like characteristics

“…As explained before, patients after heart surgery or prosthesis users prefer a slower PWS than their 'calculated' ES [ 3 ]. However, a use of BWS apparatus can reduce the metabolic rate during walking [ 13 ] and running [ 14 , 17 ] on the treadmill. Given these previous findings and our current results (Fig.…”

“…Another potential limitation was that only 30% BWS was tested. As far as we know, a short-stroke spring-like BWS was used only once in the past [ 17 ]. In association with the installed spring characteristics, more studies are necessary to understand physiological responses if more and/or less than 30% BW was supported by the spring-type BWS apparatus.…”

“…Forty healthy young males including 13 recently tested participants [ 17 ] were involved in this study. They are recreationally trained with some previous walking experiences on a treadmill.…”

“…A body suspension apparatus that lifts the participants’ torso by an elastic harness was installed surrounding a motor-driven treadmill (Fig. 1 a; Well Load 200E, Takei Scientific Instruments Co., Ltd., Niigata, Japan) [ 17 ]. A force transducer (TSA-110, Takei Scientific Instruments Co., Ltd., Japan) was situated between a controller and a spring (30 cm free length with a spring constant of 5.7 kg cm − 1 ).…”

Role of sex and stature on the biomechanics of normal and loaded walking: implications for injury risk in the military

“…The strength and significance of associations are mixed between the preferred walk-to-run transition speed and anthropometry (stature, sitting height, leg length, lower leg length, thigh girth and calf girth) [17,18,36,38]. Greater variability in stride length, frequency and duration is also observed at speeds near the preferred walk-to-run transition speed, suggesting a loss of stability in the movement pattern [39], increased rate of perceived effort [15,40] and increased muscle activity [40,41]. These findings are relevant and important to a military population marching 'in-step'.…”