Does overreaching from endurance-based training impair sleep: A systematic review and meta-analysis.

BACKGROUND: Overreaching is often linked to a deterioration in sleep quality, yet a comprehensive review is lacking. The aim of this systemic review and meta-analysis was to synthesise the literature and quantify the effect of overreaching from endurance-based training on sleep quality. METHOD: The review was conducted following the PRISMA guidelines. The final search was conducted in May 2023 using four electronic databases (Web of Science Core Collection, MEDLINE, Cochrane Central Database, SPORTDiscus). Studies were included for a qualitative review, while random-effects meta-analyses were conducted for objective and subjective sleep. RESULTS AND DISCUSSION: The search returned 805 articles. Fourteen studies were included in the systematic review; Three and eight articles were eligible for the meta-analyses (objective and subjective, respectively). On average, the overreaching protocols were sixteen days in length (6 to 28 days) and included exercise modalities such as cycling (number of studies [k] = 5), rowing (k = 4), triathlon (k = 3), running (k = 2), and swimming (k = 1). Actigraphy was the only form of objective sleep measurement used across all studies (k = 3), while various instruments were used to capture subjective sleep quality (k = 13). When comparing objective sleep quality following the overreaching intervention to baseline (or a control), there was a significant reduction in sleep efficiency (mean difference = -2.0%; 95% CI -3.2, -0.8%; Glass' Δ = -0.83; p < 0.01). In contrast, when comparing subjective sleep quality following the overreaching intervention to baseline (or a control), there was no effect on subjective sleep quality (Glass' Δ = -0.27; 95% CI -0.79, 0.25; p = 0.08). Importantly, none of the included studies were judged to have a low risk of bias. While acknowledging the need for more high-quality studies, it appears that overreaching from endurance-based training can deteriorate objective sleep without influencing the perception of sleep quality. PROTOCOL REGISTRATION: This protocol was registered in The International Prospective Register of Systematic Reviews (PROSPERO) on 21st November 2022, with the registration number CRD42022373204.

Implications of Heat Stress-induced Metabolic Alterations for Endurance Training.

Inducing a heat-acclimated phenotype via repeated heat stress improves exercise capacity and reduces athletes̓ risk of hyperthermia and heat illness. Given the increased number of international sporting events hosted in countries with warmer climates, heat acclimation strategies are increasingly popular among endurance athletes to optimize performance in hot environments. At the tissue level, completing endurance exercise under heat stress may augment endurance training adaptation, including mitochondrial and cardiovascular remodeling due to increased perturbations to cellular homeostasis as a consequence of metabolic and cardiovascular load, and this may improve endurance training adaptation and subsequent performance. This review provides an up-to-date overview of the metabolic impact of heat stress during endurance exercise, including proposed underlying mechanisms of altered substrate utilization. Against this metabolic backdrop, the current literature highlighting the role of heat stress in augmenting training adaptation and subsequent endurance performance will be presented with practical implications and opportunities for future research.

Patellar Tendon Adaptations to Downhill Running Training and Their Relationships With Changes in Mechanical Stress and Loading History.

ABSTRACT: Bontemps, B, Gruet, M, Louis, J, Owens, DJ, Miríc, S, Vercruyssen, F, and Erskine, RM. Patellar tendon adaptations to downhill running training and their relationships with changes in mechanical stress and loading history. J Strength Cond Res 38(1): 21-29, 2024-It is unclear whether human tendon adapts to moderate-intensity, high-volume long-term eccentric exercise, e.g., downhill running (DR) training. This study aimed to investigate the time course of patellar tendon (PT) adaptation to short-term DR training and to determine whether changes in PT properties were related to changes in mechanical stress or loading history. Twelve untrained, young, healthy adults (5 women and 7 men) took part in 4 weeks' DR training, comprising 10 sessions. Running speed was equivalent to 60-65% V̇O2max, and session duration increased gradually (15-30 minutes) throughout training. Isometric knee extensor maximal voluntary torque (MVT), vastus lateralis (VL) muscle physiological cross-sectional area (PCSA) and volume, and PT CSA, stiffness, and Young's modulus were assessed at weeks 0, 2, and 4 using ultrasound and isokinetic dynamometry. Patellar tendon stiffness (+6.4 ± 7.4%), Young's modulus (+6.9 ± 8.8%), isometric MVT (+7.5 ± 12.3%), VL volume (+6.6 ± 3.2%), and PCSA (+3.8 ± 3.3%) increased after 4 weeks' DR (p < 0.05), with no change in PT CSA. Changes in VL PCSA correlated with changes in PT stiffness (r = 0.70; p = 0.02) and Young's modulus (r = 0.63; p = 0.04) from 0 to 4 weeks, whereas changes in MVT did not correlate with changes in PT stiffness and Young's modulus at any time point (p > 0.05). To conclude, 4 weeks' DR training promoted substantial changes in PT stiffness and Young's modulus that are typically observed after high-intensity, low-volume resistance training. These tendon adaptations seemed to be driven primarily by loading history (represented by VL muscle hypertrophy), whereas increased mechanical stress throughout the training period did not seem to contribute to changes in PT stiffness or Young's modulus.