Abstract
While post-exercise heart rate (HR) variability (HRV) has been shown to increase in response to training leading to improvements in performance, the effect of training leading to decrements in performance (i.e., overreaching) on this parameter has been largely ignored. This study evaluated the effect of heavy training leading to performance decrements on sub-maximal post-exercise HRV. Running performance [5 km treadmill time-trial (5TTT)], post-exercise HRV [root-mean-square difference of successive normal R-R intervals (RMSSD)] and measures of subjective training tolerance (Daily Analysis of Life Demands for Athletes “worse than normal” scores) were assessed in 11 male runners following 1 week of light training (LT), 2 weeks of heavy training (HT) and a 10 day taper (T). Post-exercise RMSSD was assessed following 5 min of running exercise at an individualised speed eliciting 85% of peak HR. Time to complete 5TTT likely increased following HT (ES = 0.14 ± 0.03; p < 0.001), and then almost certainly decreased following T (ES = −0.30 ± 0.07; p < 0.001). Subjective training tolerance worsened after HT (ES = −2.54 ± 0.62; p = 0.001) and improved after T (ES = 2.16 ± 0.64; p = 0.004). In comparison to LT, post-exercise RMSSD likely increased at HT (ES = 0.65 ± 0.55; p = 0.06), and likely decreased at T (ES = −0.69 ± 0.45; p = 0.02). A moderate within-subject correlation was found between 5TTT and post-exercise RMSSD (r = 0.47 ± 0.36; p = 0.03). Increased post-exercise RMSSD following HT demonstrated heightened post-exercise parasympathetic modulation in functionally overreached athletes. Heightened post-exercise RMSSD in this context appears paradoxical given this parameter also increases in response to improvements in performance. Thus, additional measures such as subjective training tolerance are required to interpret changes in post-exercise RMSSD.
Highlights
The ability of coaches and sport science practitioners to readily and accurately predict athletic training status would assist in optimising training, since this information could be used to adjust training loads (Buchheit, 2014)
Three of the 14 completed participants were diagnosed as acutely fatigued, but not overreached, as they did not experience a decline in 5 km treadmill time trial (5TTT) performance that was greater than the natural variability in this test [i.e., CV = 1.3% (Fuller et al, 2015)] (Le Meur et al, 2014), and were excluded from further analysis so as not to
The primary finding in this study was heightened post-exercise parasympathetic modulation in functionally overreached athletes. This heightened parasympathetic modulation was able to be detected over a period of time shorter than that previously assessed, which may aid the practical application of post-exercise HR variability (HRV) assessment for monitoring athletes
Summary
The ability of coaches and sport science practitioners to readily and accurately predict athletic training status would assist in optimising training, since this information could be used to adjust training loads (Buchheit, 2014). Numerous psychological and physiological markers of training status have been evaluated over the years, their validity and/or practicality has yet to be fully established (Borresen and Lambert, 2009; Meeusen et al, 2013) Psychological measures such as the Profile of Mood Status questionnaire (McNair et al, 1971) and the Daily Analysis of Life Demands for Athletes questionnaire (Rushall, 1990) have been investigated extensively, the subjective nature of these assessments means that they are susceptible to manipulation for competition or training gain (Urhausen and Kindermann, 2002), are influenced by age and cognitive development (Groslambert and Mahon, 2006) and may be unreliable as a result of their reliance on memory recall (Shephard, 2003). Physiological parameters, including sub-maximal blood lactate concentrations, hormones and neuromotor control of movement have been shown to be altered by heavy overload training (Jacobs, 1986; Lehmann et al, 1992; Fuller et al, 2017; Greenham et al, 2018; Bellenger et al, 2019), their practicality and/or validity remains to be established as a result of either variable results, invasive assessment techniques or need for specialised/expensive equipment (Urhausen and Kindermann, 2002; Borresen and Lambert, 2009; Greenham et al, 2018)
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