This study mainly aimed to assess the interactions between locomotion and ventilation during a roller-skiing time-trial on treadmill using the double poling technique, on a breath-by-breath and poling-by-poling basis. Methods: Six (2 women and 4 men) well trained cross-country skiers performed a time-trial test roller-skiing on a motor driven treadmill and using the double-poling technique. The treadmill slope was fixed at 4% and the speed corresponded to 90% of the maximal speed achieved during a previous incremental double-poling test to exhaustion. Ventilatory flow was continuously collected by directly acquiring the optoelectronic signal from the turbine flowmeter of a portable metabolic system. Poling signal were obtained using load cells inserted under the poles handgrips. Both signale were acquired at 100Hz and synchronized together. Instantaneous breathing frequency (IBF) for each breath was calculated as the inverse of the breath duration. Instantaneous poling frequency (IPF) was similarly calculated from the poling signal. Entrainment was assessed by calculating the ratio of each IBF to the corresponding IPF. Cycles were considered to be entrained when the computed ratio was ±10% of an integer value. The data were then divided into entrained and unentrained groups, irrespective of the subject. Results: A total number of around 1700 breathing and poling cycles were collected, of whom, 4% were considered unentrained. IBF/IPF ratio was always closed to the integer value one. An important variability (i.e., high standard-deviation value) in the difference between the time at the onset of expiration phase and the time at the peak poling force (PPF) has been observed for the unentrained cycles (0.07±0.37 sec) compared to the entrained cycles (0.07±0.12 sec). Non-parametric tests (Kruskal-Wallis followed by Dunn`s multiple comparisons) showed that the PPF, the mean poling force over the poling phase (MPF) and the tidal volume (VT) were significantly higher (P=0.014, P=0.004 and P=0.012, respectively) when breathing and poling rhythms were entrained (2.66±0.47 N/kg, 1.12±0.13 N/kg and 2.16±0.41 L, respectively) compared to when they were unentrained (2.49±0.57 N/kg, 1.07±0.17 N/kg and 1.99±0.57 L). IPF was not significantly different between the entrained and unentrained groups (0.87±0.13 Hz and 0.93±0.21 Hz, respectively, P=0.146) whereas IBF was lower (P=0.013) for the entrained group compared to the unentrained one (0.87±0.13 Hz and 0.96±0.30 Hz, respectively). Discussion: The evident coordination (i.e, IBF/IPF ratio closed to one and low % of unentrained cycles) observed between ventilation and locomotion rhythms in the present study confirmed the findings of a previous study with the skating technique (1). More interestingly, these results emphasized the negative influence of unlocked locomotor and ventilatory rhythms on both breathing and poling patterns.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Published by The Norwegian School of Sport Sciences. All rights reserved.