Effect of stride length on symptoms of exercise‐induced muscle damage during a repeated bout of downhill running

Abstract

The purpose of this study was to assess the effects of changes in stride length on the symptoms of exercise-induced muscle damage (EIMD) during a repeated bout of downhill running in a group of 18 men and women. Muscle tenderness, plasma creatine kinase activity (CK) and maximal voluntary isometric force were measured before and after two downhill runs, with each run separated by 5 weeks. The first downhill run was at the preferred stride frequency (PSF). Participants were then randomly allocated to one of three sex-balanced groups with equal numbers of men and women: overstride (-8% PSF), understride (+8% PSF) and normal stride frequency for the second downhill run. Stride length had no effect (P>0.05) on muscle tenderness, CK or isometric peak force. Increases in muscle tenderness (P<0.001) and CK were lower (P<0.05) following the second downhill run, although there was no difference in the pattern and extent of the strength decrement between the two runs. There were also no differences (P>0.05) in muscle tenderness, CK or the relative strength loss between the men and the women. Results suggest that the symptoms of EIMD are unaffected by gender and small alterations to the normal stride pattern during constant velocity downhill running. The observation that muscle tenderness and CK were reduced following a repeated bout of similar eccentric exercise is consistent with the phenomenon known as the 'repeated bout effect' of muscle damage.

The effect of glycogen reduction on cardiorespiratory and metabolic responses during downhill running

“…Blind selection was used to randomly allocate run order (NORM first, n = 5; RED first, n = 7), and only the first run was preceded by familiarisations. A repeat bout of the downhill running protocol has been shown not to affect knee extensor strength in a similar cohort 5 weeks later (Eston et al 2000 ). Similarly, we found no order effect between downhill runs for maximal force loss (P = 0.12, d = 0.11).…”

“…After a 5 min warm up (1 % gradient at 8 km h ), participants performed five, 8 min stages of downhill running, separated by 2 min recovery periods (1 % gradient at 8 km h ). Previously used with young individuals, at a fixed running speed (11.3 km h ), the protocol was effective in inducing knee extensor soreness and maximal force loss up to 72 h later (Eston et al 2000 ). Expired gas was sampled in the final 60 s of each stage, and HR, RPE and fingertip blood in the final 30 s. Between conditions, the same footwear and treadmill were used in a temperature controlled laboratory (19-21 °C).…”

Changes in neutrophil count, creatine kinases and muscle soreness after repeated bouts of downhill running

“…10 So differences in mode of exercise could induce differences in the target of injury. 5 Whether this could induce differences in aspects of inflammation, such as differences in neutrophilia, is currently unknown.…”

“…With regard to repeated bouts of eccentrics, CK has consistently been shown to be significantly lower after the second bout of eccentrics. 3,8,14,18,21 However, in previous downhill running studies 3,5,21 CK was only measured at 24-h intervals; whether differences in serum CK are evident at an earlier time point after downhill running has not been investigated. Thus, an additional purpose of this study was to assess total circulating CK at 3-h intervals during the initial 12 h, as well as at 24-h intervals for 6 d, following both downhill runs.…”

Gender Differences after Downhill Running for Voluntary Isometric Contractions of Knee Extensor Muscles using Surface EMG

“…Speed and gradient of the treadmill for the downhill run was set at 60%V max and -12%, respectively. Subjects ran 5 bouts of 8 min separated by a 2 min recovery (31) in which subjects remained standing on the non-moving part of the treadmill.…”