Effect of fatigue on spontaneous velocity variations in human middle-distance running: use of short-term Fourier transformation

Abstract

Best performances in middle-distance running are characterized by coefficients of variation of the velocity ranging from 1% to 5%. This seems to suggest that running at constant velocity is a strain inducing an increase in physiological variables such as oxygen uptake. This study tested three questions. (l) Does velocity variability during a middle-distance all-out run increase with fatigue? (2) Does velocity variability alter the slow phase of the oxygen kinetic because of small spontaneous recoveries, compared with the same distance run at constant velocity? (3) Is a maintained average velocity over a given distance enhanced by a variable-pace rather than by a constant-pace? Ten long-distance runners performed two series of all-out runs over the distance (previously determined) which they could cover maintaining a velocity equal to 90% of that eliciting maximal oxygen consumption. In the first series ( free-pace) the subjects were asked to run as fast as possible, without any predetermined velocity profile. In the second series, the same distance was covered at a constant velocity (equal to the average in the previous free-pace run), set by a cyclist preceding the runner. Short-term Fourier transform was used to analyse velocity oscillations. Our results show that: (1) for all subjects, the mean energy spectrum did not change throughout the free-pace runs, suggesting that velocity variability did not increase with fatigue (2-way ANOVA, P=0.557); (2) the kinetic of oxygen uptake and its asymptote were not changed during the free-pace runs compared to the constant-velocity run; (3) performance was not significantly improved by free-pace average velocity [mean (SD) 4.22 (0.47) compared to 4.25 (0.52) m x s(-1) for constant and free-pace respectively, t=-0.58, P=0.57]. These results indicate that during middle-distance running, fatigue does not increase variations in velocity, and free-pace changes neither performance nor the oxygen kinetic.

Energetics of Middle-Distance Running Performances in Male and Female Junior Using Track Measurements

“…It is well known, however, that VO 2 max is lower in cycling compared with a running exercise [6] and that the energy cost of running on a treadmill is not similar to running on a track [7,8]. Since this study was performed 10 years ago [5], technological progresses have made it possible to measure all the factors in field experiments by using breath-by-breath portable oxygen analyzers [8][9][10][11][12][13]. Elite athletes, who generally are not available for testing in laboratory conditions, are often more open to field tests.…”

Nonlinear Dynamics of Heart Rate and Oxygen Uptake in Exhaustive 10,000 m Runs: Influence of Constant vs. Freely Paced

“…They used Fast Fourier transform to analyze the run speed and the physiological response ( and heart rate) variations. That study [3] suggested that an athlete might unconsciously modify his velocity to maintain a physiological steady state. In all subjects, no apparent systematization in running-speed changes was reported.…”

“…The analysis of the adaptations of the autonomic nervous system activity has been widely studied through heart rate variability with Fourier transform to appreciate the autonomic control of heart rate variability during and after exercise [31][32][33]. Only one study [3] addressed spontaneous velocity changes with fatigue in all-out runs over the distance limit (dlim) at free spontaneous velocity or the same average, but constant, velocity (the minimal velocity that elicits max in an incremental test (v max ). They used Fast Fourier transform to analyze the run speed and the physiological response ( and heart rate) variations.…”

“…Although the concept of even pacing is well accepted in athletics, the best performances in middle-distance running (800-10,000 m) are actually characterized by a speed variability. If one considers the most recent three world records for middle-and long-distance running, within-race velocity varies by up to 5% [2][3][4]. There is some evidence of a continual negotiation carried out by the athlete designed to exhaust anaerobic energetic reserves just at the end of the race to reach critically low values for muscle glycogen and/or to reach critical levels of homeostatic disturbances only at the end [5][6][7].…”

“…Indeed, most studies have described and HR dynamics with classical linear models [10], but the impact on the physiological functions can be completed by a possible modification of the regularity of signals as heart rate (HR) for the cardiac function [3]. The main interest of such nonlinear dynamics analysis has been to appreciate the response to unpredictable stimuli and stresses [11].…”