Author(s): ENGELBORGHS, S., DE SMET, S., Institution: KU LEUVEN, Country: BELGIUM, Abstract-ID: 2063

INTRODUCTION:
High-load exercise training not accompanied by adequate recovery may induce transient decline in exercise performance together with prolonged fatigue, a condition known as overreaching. Overreaching has also been linked to a broad range of physiological and psychological disturbances. However, this multidimensional phenotype has not yet been examined comprehensively within a single trial.
METHODS:
This preliminary analysis includes 19 participants from an ongoing RCT (target: n=45). 19 recreationally active men were randomly assigned to (i) control (CON, n=4), (ii) 8 weeks of moderate-load training with 4 supervised cycling training sessions a week (MOD, n=7), or (iii) 4 weeks of moderate-load (4 sessions/week) followed by 4 weeks of high-load (8 sessions/week) cycling training (HIGH, n=8) anticipated to induce overreaching. The study intervention is followed by a 10-day taper. Experimental assessments were conducted at baseline (T1), after 4 weeks (T2), after 8 weeks (T3), and after taper (T4). Assessments included evaluation of exercise performance (30-s sprint and 30-min time trial), maximum rate of blood lactate production (vLamax), maximal heart rate, heart rate variability (RMSSD), self-reported mood disturbances (POMS, lower score is favorable), self-reported recovery and stress (RESTQ, higher score is favorable), systemic inflammation (hsCRP), and glucose homeostasis (HOMA-IR: lower is favorable; Matsuda-index: higher is favorable). Overreaching was defined as reduced exercise performance (30-sec sprint or 30-min time trial) combined with decreased ‘Energy Index’ (POMS) between T2 and T3, with changes exceeding measurement error. Descriptive statistics (means +/- SD) with effects sizes (Cohen’s d) characterize intervention effects between T2 and T3.
RESULTS:
No participants in CON or MOD, but 4 participants in HIGH were classified as overreached. Mood disturbance in HIGH participants not categorized as overreached (NO, n = 4) decreased by 4 +/- 8 points (d=-0.6), whilst increased by 24 +/- 19 points (d=1.2) in HIGH participants categorized as overreached (O, n = 4). Similar trajectories were found for recovery-stress balance (NO: -21 +/- 40 points, d=-0.5; O: -54 +/- 55 points, d=-1.0), maximal heart rate (NO: +1 +/- 4 bpm, d=0.2; O: -2 +/- 1 bpm, d=-1.2), RMSSD (NO: -3 +/- 6 ms, d=-0.5; O: -39 +/- 53 ms, d=-0.7), and hsCRP (NO: +1.3 +/- 2.5 mg/L, d=0.5; O: +3 +/- 6.0 mg/L, d=0.5). Preliminary data did not suggest overreaching to impair vLamax (NO: -0.0 +/- 0.2 mmol/L/s, d=-0.18; O: -0.0 +/- 0.1 mmol/L/s, d=-0.37), HOMA-IR (NO: +0.0 +/- 0.2, d=1.6; O: -0.1 +/- 0.2, d=-1.0), or Matsuda-index (NO: -0.50 +/- 1.18, d=-1.2; O: -0.82 +/- 0.88 d=-0.1).
CONCLUSION:
Preliminary data of this ongoing trial indicate that overreaching may represent a complex multisystem phenomenon, but conclusions await study completion and further in-depth analyses of biosamples (blood, saliva, muscle, urine, stool) characterizing the multisystem phenotype and its underlying mediators.