Age does not influence erector spinae muscle activity during treadmill walking and running in healthy adults

Introduction
Changes in motor control patterns [1] and muscle synergies [2] are known to occur with ageing. Although the activation of trunk musculature during walking and running has been evaluated previously [3], the effect of ageing on muscle activity during locomotion has primarily focussed on the lower limb muscles. Therefore, the purpose of this study was to report activation of the spinal extensor muscles during walking and running in a group of young and a group of mature male and female healthy adults.

Methods
Twelve young (age 18-25 years) and 12 mature (age 45-60 years) adults were recruited. Kinematic data were collected using a 10-camera motion capture system and surface electromyography (sEMG) was obtained from the Erector Spinae longissimus muscle (left and right sides). sEMG and kinematic data were collected synchronously during treadmill walk and run (three trials of 10s each). sEMG data were full-wave rectified, de-meaned and re-sampled to match kinematic data. A 4th order 20Hz low pass Butterworth filter was applied to obtain linear envelopes. sEMG data were normalised to the dynamic peak EMG. Data were cut into motion cycles and maximum, minimum, range, and mean normalised sEMG amplitude were obtained and the two groups compared using independent t-tests.

Results
Mean, maximum and minimum muscle activity was greater in the mature group, but no significant differences were found.

Table 1Average (± standard deviation) of the Maximum, minimum, range, and mean normalised erector spinae muscle activity (%)

Discussion
Changes in muscle activity often observed with ageing were not identified in the spinal extensors in healthy mature adults in this study. Future work should assess whether this finding applies to adults older than 65 years.

Acknowledgements
Austrian Science Fund (P24020).