Ageing does not affect flexion relaxation of erector spinae.

Erector spinae (ES) activity during trunk flexion in 22 young (20-25 years) and 16 older (60-92 years) normal females was examined with surface EMG. The trunk movements and simultaneous EMG oscillograph of ES were recorded with two synchronised video cameras. The ES relaxed at the critical position (CP) which was 67 and 82 per cent of full trunk flexion for young and older subjects respectively. The vertebral movements to the CP were not different between groups, but the older subjects demonstrated more hip movement to the CP and less full trunk flexion range. The implications of these age related changes in trunk kinematics are yet to be developed with further clinical studies.