Inter-limb co-ordination in incline walking

The presence of two distinct patterns of inter-limb co-ordination while walking has shown a transition from a double to single arm swing per stride occurring as stride frequency increased from super slow to faster speeds (Craik et al, 1976; Wagenaar and Van Emmerik, 1994). The purpose of this experiment was to explore whether changes in incline (while holding stride frequency constant) would elicit the same type of transition in inter-limb co-ordination. Four (4) college-aged participants walked at a constant velocity (0.8mph) on a treadmill while the incline was increased from 0-9% in six incremental steps of 1.5%. The participants walked at each incline for 30 seconds with arm swing and stride frequency assessed for the final 5 strides at each of the seven inclines. The results revealed stride frequency changes within the 5 strides and across the inclines. These results support previous literature that demonstrated the 2:1 frequency relation. The change in incline also caused a shift in inter-limb co-ordination pattern. Participants did not exhibit a switch to another stable mode (e.g. 1:1), however phase drifting in frequency ratios below 2:1 and above 1:1 was observed instead. A strong negative correlation between the frequency ratio and the variability of the arm swing revealed that lower arm swing variability values were associated with the 2:1 frequency ratio. We interpret these data as supporting modulation of the humeral extension component of the arm swing in order to facilitate functional compensations for incline walking.