Impaired neuromusculoskeletal response to training stimuli associated with low energy availability: a systematic review.

Abstract

Low energy availability (LEA) impairs musculoskeletal health, with emerging evidence of impaired neuromusculoskeletal adaptations to training. We aimed to synthesise the existing evidence examining neuromusculoskeletal responses to training stimuli among individuals with LEA. Systematic review (PROSPERO 603258). Six databases were searched on 4 November 2024 (total n=6399; duplicates n=2811; articles to screen n=3388). Search terms included the population and training-related exposures. Two blinded, independent reviewers screened articles using the Covidence web-based tool. Original articles written in English with any form of neuromusculoskeletal responses to training stimuli (premeasures and postmeasures) assessed among individuals aged ≥10 years with LEA were included. Study details, methodological quality (Physiotherapy Evidence Database, PEDro scale) and descriptive summaries with change percentages by time point and LEA status were extracted. 21 studies met inclusion criteria (total participants: 536; 44% males, 56% females; PEDro: 5±2). Inconsistencies in LEA thresholds and criteria, exercise exposures and follow-up time frames precluded pooled analyses. All studies examined changes in lean muscle or fat-free mass (FFM), with seven also examining functional or activity-specific performance, and fewer concurrently examining strength, limb circumference, cellular-level or subjective neuromusculoskeletal measures. 10 studies identified that those with LEA had impaired lean mass/FFM responses (-1% to -5%), and 10 found no substantial changes over time (<1%). Six studies identified functional/sport-specific impairments over time among those with LEA (-4% to -10%). All remaining primary adaptations (strength, limb circumference, cellular-level and subjective measures) were impaired with LEA. These findings are clinically meaningful to consider, particularly for LEA-related impaired responses to rehabilitation targeting muscle hypertrophy and strength. Coaches, athletes and clinicians should be aware of the evidence suggesting LEA impairs neuromusculoskeletal training responses.