title: Monitoring high-intensity endurance training using neuromuscular excitability to recognize overtraining.
abstract: The minimal rectangular current pulse that produces a single contraction of reference muscles at different pulse durations has been recommended as a marker of the neuromuscular excitability (NME) of skeletal muscles. NME is improved in well-trained, non-fatigued endurance athletes and deteriorates after prolonged heavy exercise and high-volume overtraining. The hypothesis was tested that a deterioration in NME also indicates an early stage in the overtraining process during high-intensity endurance training. Six subjects participated for 40-60 min per day in a 6-week, 6-days-per-week, intensive, steady-state and interval training program using a cycle ergometer. Training was stopped each day on volitional exhaustion. On day 7 of each week training was of low intensity for about 30-40 min. Submaximum and maximum power output were significantly increased after 3 weeks, but there was no further improvement, rather a deterioration after week 6 compared to week 3. Even after 2 weeks of regeneration no supercompensation was evident, rather a decrease in maximum power output. NME was slightly improved after 3 weeks, but deteriorated after 6 weeks, and was again normalized after 2 weeks of regeneration. The discrepancy between normalization of NME and still-deteriorated performance ability after 2 weeks of regeneration reflects additional significant, and probably central mechanisms that explain persistent performance incompetence. Deterioration in NME may indicate an early stage in the overtraining process during high-volume as well as high-intensity endurance overtraining, but normalization does not necessarily indicate sufficient regeneration.
authors.affiliation: Department of Sports Medicine, Medical Hospital, University of Ulm, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Lehmann
authors.forename: S
authors.initials: S
authors.lastname: Baur
authors.forename: N
authors.initials: N
authors.lastname: Netzer
authors.forename: U
authors.initials: U
authors.lastname: Gastmann
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005221:Fatigue / Q000517:prevention & control*; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D013177:Sports / Q000502:physiology*