The Development of Functional Overreaching Is Associated with a Faster Heart Rate Recovery in Endurance Athletes

Purpose The aim of the study was to investigate whether heart rate recovery (HRR) may represent an effective marker of functional overreaching (f-OR) in endurance athletes. Methods and Results Thirty-one experienced male triathletes were tested (10 control and 21 overload subjects) before (Pre), and immediately after an overload training period (Mid) and after a 2-week taper (Post). Physiological responses were assessed during an incremental cycling protocol to exhaustion, including heart rate, catecholamine release and blood lactate concentration. Ten participants from the overload group developed signs of f-OR at Mid (i.e. -2.1 ± 0.8% change in performance associated with concomitant high perceived fatigue). Additionally, only the f-OR group demonstrated a 99% chance of increase in HRR during the overload period (+8 ± 5 bpm, large effect size). Concomitantly, this group also revealed a >80% chance of decreasing blood lactate (-11 ± 14%, large), plasma norepinephrine (-12 ± 37%, small) and plasma epinephrine peak concentrations (-51 ± 22%, moderate). These blood measures returned to baseline levels at Post. HRR change was negatively correlated to changes in performance, peak HR and peak blood metabolites concentrations. Conclusion These findings suggest that i) a faster HRR is not systematically associated with improved physical performance, ii) changes in HRR should be interpreted in the context of the specific training phase, the athletes perceived level of fatigue and the performance response; and, iii) the faster HRR associated with f-OR may be induced by a decreased central commandand by a lower chemoreflex activity

The reliability and usefulness of an individualised submaximal shuttle run test in elite rugby league players

Purpose: The aim of the present study was to examine the reliability and usefulness of a proposed 4-min individualised submaximal shuttle run test (SSR) in elite rugby league players. Materials and methods: Twenty-two elite rugby league players competing in the National Rugby League competition (23.2\ua0±\ua03.4\ua0years, 186.8\ua0±\ua05.4\ua0cm, 100.2\ua0±\ua08.5\ua0kg) performed the SSR twice, seven days apart (test–retest design). The SSR was prescribed as 75% of the average speed during a 1500-m time trial. Exercise heart rate was calculated as the average heart rate (HR) over the final 30 s (HRex). Seated HR recovery (HRR) was recorded at 1- (HRR) and 2-min (HRR) post-exercise. Data were analysed with magnitude-based inferences. Results: Test–retest typical errors were moderate for HRex (1.2 percentage points; 90% confidence limits: 1.0–1.7), HRR (3.4; 2.7–4.6) and HRR (2.9; 2.3–3.9). Intraclass correlation coefficients were extremely high for HRex (0.91; 0.78–0.94) and very high for both HRR (0.80; 0.61–0.90) and HRR (0.84; 0.69–0.92). Thresholds for an individual change that would be likely small and greater than the typical error were ±1.8 (percentage points), ±4.6 and ±4.1 for HRex, HRR and HRR, respectively. Conclusions: The SSR demonstrates acceptable reliability in the assessment of HRex and HRR, thus demonstrating its potential usefulness for monitoring fitness and fatigue in elite rugby league players