Shock accelerations and attenuation in downhill and level running

Objective. A study was conducted to investigate the possible effects of fat igue on the heel strike-initiated shock accelerations and on attenuation of these shocks along the body during eccentric muscle contractions. Design. Level and decline running on a treadmill were used to acquire the e xperimental data on the foot strike-initiated shock accelerations. Background. Eccentric contractions of the lower limb muscles in combination with shock generation and propagation during downhill running and muscle f atigue may diminish their ability to dissipate and attenuate loading on the system. Methods. Fourteen young healthy males ran on a treadmill at a speed exceedi ng their anaerobic threshold by 5% for 30 min, as follows: (a) level runnin g and (b) downhill running with a decline angle of -4 degrees. The foot str ike-induced shock accelerations were recorded every five minutes on the tib ial tuberosity and sacrum. Fatigue was monitored by means of the respirator y parameters. Results. The downhill running related with eccentric muscle contractions wa s associated with increased shock propagation from the tibial tuberosity to the sacrum levels, even though fatigue did not develop. Conclusions. Shock propagation from the tibial tuberosity to the sacrum is augmented due to the eccentric action of the muscles, without metabolic fat igue development.