Clint R. Bellenger

Improved heart rate recovery despite reduced exercise performance following heavy training: A within-subject analysis

OBJECTIVES The recovery of heart rate (HRR) after exercise is a potential indicator of fitness which has been shown to respond to changes in training. This study investigated the within-individual association between HRR and exercise performance following three different training loads. DESIGN 11 male cyclists/triathletes were tested after two weeks of light training, two weeks of heavy training and two days of rest. METHODS Exercise performance was measured using a 5-min maximal cycling time-trial. HRR was measured over 60s during supine recovery. RESULTS Exercise performance decreased 2.2±2.5% following heavy training compared with post-light training (p=0.01), and then increased 4.0±4.2% following rest (p=0.004). Most HRR indices indicated a more rapid recovery of heart rate (HR) following heavy training, and reverted to post light training levels following two days of rest. HRR indices did not differ between post-light training and after the rest period (p>0.6). There were inverse within-subject relationships between indices of HRR and performance (r=-0.6, p≤0.004). Peak HR decreased 3.2±5.1bpm following heavy training (p=0.06) and significantly increased 4.9±4.3bpm following recovery (p=0.004). There was a moderate within-subject relationship between peak HR and exercise performance (r=0.7, p≤0.001). Controlling for peak HR reduced the relationships between HRR and performance (r=-0.4-0.5, p<0.05). CONCLUSIONS This study demonstrated that HRR tracks short-term changes in exercise performance within-individuals, such that increases in HRR are associated with poorer exercise performance following heavy training. Peak HR can be compromised under conditions of fatigue, and needs to be taken into account in HRR analyses.

Contextualizing Parasympathetic Hyperactivity in Functionally Overreached Athletes with Perceptions of Training Tolerance

PURPOSE Heart-rate variability (HRV) as a measure of autonomic function may increase in response to training interventions leading to increases or decreases in performance, making HRV interpretation difficult in isolation. This study aimed to contextualize changes in HRV with subjective measures of training tolerance. METHODS Supine and standing measures of vagally mediated HRV (root-mean-square difference of successive normal RR intervals [RMSSD]) and measures of training tolerance (Daily Analysis of Life Demands for Athletes questionnaire, perception of energy levels, fatigue, and muscle soreness) were recorded daily during 1 wk of light training (LT), 2 wk of heavy training (HT), and 10 d of tapering (T) in 15 male runners/ triathletes. HRV and training tolerance were analyzed as rolling 7-d averages at LT, HT, and T. Performance was assessed after LT, HT, and T with a 5-km treadmill time trial (5TTT). RESULTS Time to complete the 5TTT likely increased after HT (effect size [ES] ± 90% confidence interval = 0.16 ± 0.06) and then almost certainly decreased after T (ES = -0.34 ± 0.08). Training tolerance worsened after HT (ES ≥ 1.30 ± 0.41) and improved after T (ES ≥ 1.27 ± 0.49). Standing RMSSD very likely increased after HT (ES = 0.62 ± 0.26) and likely remained higher than LT at the completion of T (ES = 0.38 ± 0.21). Changes in supine RMSSD were possible or likely trivial. CONCLUSIONS Vagally mediated HRV during standing increased in response to functional overreaching (indicating potential parasympathetic hyperactivity) and also to improvements in performance. Thus, additional measures such as training tolerance are required to interpret changes in vagally mediated HRV.

Monitoring athletic training status using the maximal rate of heart rate increase

OBJECTIVES Reductions in maximal rate of heart rate increase (rHRI) correlate with performance reductions when training load is increased. This study evaluated whether rHRI tracked performance changes across a range of training states. DESIGN Prospective intervention. METHODS rHRI was assessed during five min of cycling at 100W (rHRIcyc) and running at 8km/h (rHRIrun) in 13 male triathletes following two weeks of light-training (LT), two weeks of heavy-training (HT) and a two-day recovery period (RP). A five min cycling time-trial assessed performance and peak oxygen consumption (V˙O2peak). RESULTS Performance likely decreased following HT (Effect size±90% confidence interval=-0.18±0.09), then very likely increased following RP (0.32±0.14). rHRIcyc very likely decreased (-0.48±0.24), and rHRIrun possibly decreased (-0.33±0.48), following HT. Changes in both measures were unclear following RP. Steady-state HR was almost certainly lower (-0.81±0.31) during rHRIcyc than rHRIrun. A large correlation was found between reductions in performance and rHRIrun (r±90%; CI=0.65±0.34) from LT to HT, but was unclear for rHRIcyc. Trivial within-subject correlations were found between rHRI and performance, but the strength of relationship between rHRIrun and performance was largely associated with V˙O2peak following LT (r=-0.58±0.38). CONCLUSIONS Performance reductions were most sensitively tracked by rHRIrun following HT. This may be due to rHRIrun being assessed at a higher intensity than rHRIcyc, inferred from a higher steady-state HR and supported by a stronger within-subject relationship between rHRIrun and performance in individuals with a lower V˙O2peak, in whom the same exercise intensity would represent a greater physiological stress. rHRI assessed at relatively high exercise intensities may better track performance changes.

Tracking Performance Changes With Running-Stride Variability When Athletes Are Functionally Overreached

PURPOSE 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 HT14 and 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.

Training loads in typical junior-elite tennis training and competition: implications for transition periods in a high-performance pathway

ABSTRACT The purpose of this study was to describe the differences in training and competition loads at three distinct development levels in a junior-elite tennis academy. A total of 39 junior-elite tennis players were recruited from three squads; U/12, U/15 and U/18. Metrics of global positioning systems, accelerometer microtechnology and hitting demands were quantified to determine the external load. Ratings of perceived exertion (RPE) were used to quantify internal training and competition loads. Two training sessions and one competition match were quantified. The results showed an increase in training hitting demands as age increased from the U/15–U/18 squad (p < 0.05). Serve loads were greater in competition compared to training across all squads (p < 0.05). Perceptions of exertion were greater in competition for the U/12 males (p < 0.01) with the U/15 males showing higher RPE in training (p < 0.05). No differences in perceptions of exertion were seen between female groups in training however, the U/15 females found competition less demanding than training (p < 0.05). Overall, the findings suggest practitioners be aware that the U/15–U/18 transition involves significant increases in hitting loads.

Optimization of Maximal Rate of Heart Rate Increase Assessment in Runners

ABSTRACT Purpose: Correlations between fatigue-induced changes in exercise performance and maximal rate of heart rate (HR) increase (rHRI) may be affected by exercise intensity during assessment. This study evaluated the sensitivity of rHRI for tracking performance when assessed at varying exercise intensities. Method: Performance (time to complete a 5-km treadmill time-trial [5TTT]) and rHRI were assessed in 15 male runners following 1 week of light training, 2 weeks of heavy training (HT), and a 10-day taper (T). Maximal rate of HR increase (measured in bpm·s−1) was the first derivative maximum of a sigmoidal curve fit to HR data recorded during 5 min of running at 8 km·h−1 (rHRI8km·h−1), and during subsequent transition to 13 km·h−1 (rHRI8–13km·h−1) for a further 5 min. Results: Time to complete a 5-km treadmill time-trial was likely slower following HT (effect size ± 90% confidence interval = 0.16 ± 0.06), and almost certainly faster following T (–0.34 ± 0.08). Maximal rate of HR increase during 5 min of running at 8 km·h−1 and rHRI8–13km·h−1 were unchanged following HT and likely increased following T (0.77 ± 0.45 and 0.66 ± 0.62, respectively). A moderate within-individual correlation was found between 5TTT and rHRI8km·h−1 (r value ± 90% confidence interval = –.35 ± .32). However, in a subgroup of athletes (n = 7) who were almost certainly slower to complete the 5TTT (4.22 ± 0.88), larger correlations were found between the 5TTT and rHRI8km·h−1 (r = –.84 ± .22) and rHRI8–13km·h−1 (r = –.52 ± .41). Steady-state HR during rHRI assessment in this group was very likely greater than in the faster subgroup (≥ 1.34 ± 0.86). Conclusion(s): The 5TTT performance was tracked by both rHRI8km·h−1 and rHRI8–13km·h−1. Correlations between rHRI and performance were stronger in a subgroup of athletes who exhibited a slower 5TTT. Individualized workloads during rHRI assessment may be required to account for varying levels of physical conditioning.

Detrended fluctuation analysis detects altered coordination of running gait in athletes following a heavy period of training

OBJECTIVES To investigate whether functional overreaching affects locomotor system behaviour when running at fixed relative intensities and if any effects were associated with changes in running performance. DESIGN Prospective intervention study. METHODS Ten trained male runners completed three training blocks in a fixed order. Training consisted of one week of light training (baseline), two weeks of heavy training designed to induce functional overreaching, and ten days of light taper training designed to allow athletes to recover from, and adapt to, the heavy training. Locomotor behaviour, 5-km time trial performance, and subjective reports of training status (Daily Analysis of Life Demands for Athletes (DALDA) questionnaire) were assessed at the completion of each training block. Locomotor behaviour was assessed using detrended fluctuation analysis of stride intervals during running at speeds corresponding to 65% and 85% of maximum heart rate (HRmax) at baseline. RESULTS Time trial performance (effect size ±95% confidence interval (ES): 0.16±0.06; p<0.001), locomotor behaviour at 65% HRmax (ES: -1.12±0.95; p=0.026), and DALDA (ES: 2.55±0.80; p<0.001) were all detrimentally affected by the heavy training. Time trial performance improved relative to baseline after the taper (ES: -0.16±0.10; p=0.003) but locomotor behaviour at 65% HRmax (ES: -1.18±1.17; p=0.048) and DALDA (ES: 0.92±0.90; p=0.045) remained impaired. CONCLUSIONS Locomotor behaviour during running at 65% HRmax was impaired by functional overreaching and remained impaired after a 10-day taper, despite improved running performance. Locomotor changes may increase injury risk and should be considered within athlete monitoring programs independently of performance changes.

Correction to: The effect of functional overreaching on parameters of autonomic heart rate regulation

The original version of this article unfortunately contained a mistake. The presentation of Equation was incorrect.