Tracking Performance Changes With Running-Stride Variability When Athletes Are Functionally Overreached.
OBJECTIVE
Stride-to-stride fluctuations in running-stride interval display long-range correlations that break down in the presence of fatigue accumulated during an exhaustive run. The purpose of the study was to investigate whether long-range correlations in running-stride interval were reduced by fatigue accumulated during prolonged exposure to a high training load (functional overreaching) and were associated with decrements in performance caused by functional overreaching.


METHODS
Ten trained male runners completed 7 d of light training (LT7), 14 d of heavy training (HT14) designed to induce a state of functional overreaching, and 10 d of light training (LT10) in a fixed order. Running-stride intervals and 5-km time-trial (5TT) performance were assessed after each training phase. The strength of long-range correlations in running-stride interval was assessed at 3 speeds (8, 10.5, and 13 km/h) using detrended fluctuation analysis.


RESULTS
Relative to performance post-LT7, time to complete the 5TT was increased after HT14(+18 s; P < .05) and decreased after LT10(-20 s; P = .03), but stride-interval long-range correlations remained unchanged at HT14and LT10(P > .50). Changes in stride-interval long-range correlations measured at a 10.5-km/h running speed were negatively associated with changes in 5TT performance (r -.46; P = .03).


CONCLUSIONS
Runners who were most affected by the prolonged exposure to high training load (as evidenced by greater reductions in 5TT performance) experienced the greatest reductions in stride-interval long-range correlations. Measurement of stride-interval long-range correlations may be useful for monitoring the effect of high training loads on athlete performance.
Joel T
JT
Fuller
Clint R
CR
Bellenger
Dominic
D
Thewlis
John
J
Arnold
Rebecca L
RL
Thomson
Margarita D
MD
Tsiros
Eileen Y
EY
Robertson
Jonathan D
JD
Buckley
D000328:Adult; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D064797:Physical Conditioning, Human / Q000379:methods*; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*
fatigue; long-range correlation; nonlinear dynamics; overreaching; overtraining syndrome