Abstract
This pilot study investigated whether a 10-week running program (10wkRP), which reduced the oxygen cost of running, affected resultant ground reaction force (GRF), leg axis alignment, joint moment characteristics, and gear ratios. Ten novice, female runners completed a 10wkRP. Running kinematics and kinetics, in addition to oxygen consumption ( V ˙ O 2 ) during steady-state running, were recorded pre- and post-10wkRP. V ˙ O 2 decreased (8%) from pre-10wkRP to post-10wkRP. There was a better alignment of the resultant GRF and leg axis at peak propulsion post-10wkRP compared with pre-10wkRP (10.8 ± 4.9 vs 1.6 ± 1.2°), as the resultant GRF vector was applied 7 ± 0.6° (P = 0.008) more horizontally. There were shorter external ankle moment arms (24%) and smaller knee extensor moments (23%) at peak braking post-10wkRP. The change in V ˙ O 2 was associated with the change in alignment of the resultant GRF and leg axis (rs = 0.88, P = 0.003). As runners became more economical, they exhibited a more aligned resultant GRF vector and leg axis at peak propulsion. This appears to be a self-optimization strategy that may improve performance. Additionally, changes to external ankle moment arms indicated beneficial low gear ratios were achieved at the time of peak braking force.
Highlights
Lowering the oxygen cost of running has been associated with improved running performance (Conley and Krahenbuhl, 1980)
There was a positive relationship between the change in VO2 and the change in alignment of the resultant ground reaction force (GRF) and leg axis at peak propulsive force
VO2, when these participants were removed from the dataset the positive relationship was still identifiable (Figure 2b). This pilot study examined whether changes in running economy were associated with changes in alignment of the resultant GRF and leg axis and consequent changes in joint moment characteristics after a 10wkRP
Summary
Lowering the oxygen cost of running has been associated with improved running performance (Conley and Krahenbuhl, 1980). It is well known that generating muscular force requires energy, and incurs an oxygen cost (Kram and Taylor, 1990; Taylor, Heglund, McMahon and Looney, 1980). Alterations to lower limb running mechanics that affect muscular force-generating requirements are likely to influence the oxygen cost of running and running performance. Studies have identified certain mechanical characteristics of running that are associated with the oxygen cost of running (Moore, Jones and Dixon, 2012; Moore, Jones and Dixon, 2014; Scholz, Bobbert, Van Soest, Clark and Van Heerden, 2008; Williams and Cavanagh, 1987). Some are modifiable and can be changed, such as kinetics (Moore et al, 2012), and others are an interaction of both, such as ‘gear ratios’
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