Power distribution, performance changes and bioelectrical impedance properties during the preparation period of professional cyclists

Abstract

Introduction Athletic training improves exercise performance and modifies body composition. The influence of training volume and intensity during the general preparation period on performance and body composition has not been extensively studied in cyclists. Thus, this study aimed to investigate performance changes as well as changes in the body composition and bioelectrical impedance properties during a three-month training period with varying training volume and intensity.  Methods Eight professional road cyclists participated in the study. After a one-month off season and before starting with their seasonal preparation period, bioelectrical impedance vector analyses (BIVA) and skinfold thickness measurements (9 sites) were performed at T0, T10 (after a month from T0), T40, T68. The bioelectrical values analyzed were Reactance/height (Xc/h), Impedance(IMP). Training volume and intensity (4 zones: 500, Metcalfe et al. 2016) as well as the Training Stress Score (TSS) were monitored at T10, T40, T68. Detailed data acquisition was done only for the last ten days during the first period. We used training data with the Training Peaks Software (Peaksware LLC, Lafayette, CO, USA) and determined the functional threshold power (FTP), the functional reserve capacity (FRC) and the peak power during 5 s (P5s), 5 min (P5min), 20 min (P20min) and 60 min (P60min).  Results Total training volume decreased from T40 to T68(distance: 2,720±270 km to 2,060±200 km; climbing: 30,400±9324 m to 16,560±6,690 m; time: 6,142±1100 min to 3,890±90 min; external work: 63,035±10,385 J to 42,628±4,338 J; p 500 watts training was completed. The phase angle and the reactance that are biomarkers of muscle function (Norman et al. 2012) improved over the 68 days of training period. Interestingly, at T10, vector length tended to increase which indicates that body water content declined (Lukaski 2013; Piccoli et. 1994) while body weight decreased. Conversely, at T40, vector length slightly decreased that indicates body water volume was restored, whereas no significant changes in body weight occurred. We hypothesize that the body fluid and weight losses from T0 are due to a negative energy balance (hypocaloric diet + increased energy expenditure). Heydenreich et al. (2017) noted that during the preparation phase the athletes often reduce their energy intake to reduce their body weight. After increasing training volume and intensity (T40), body fluid increased which is in accordance with reports showing that intensified training and increasing physical strain leads to body fluid gains (Pollastri et al. 2016; Sawka et al. 2000). We conclude that bioelectrical impedance is a practical method to monitor body water changes in response to physical training.