title: Non-invasive assessment of muscle fiber conduction velocity during an incremental maximal cycling test.
abstract: Muscle fiber conduction velocity (MFCV) gives critical information on neuromuscular control and can be considered a size principle parameter, being suggestive of motor unit recruitment strategies. MFCV has been recently measured during constant-load sub-maximal cycling exercise and was found to correlate positively with percentage of type I myosin heavy chain. The aim of this study was to test the hypothesis that MFCV measured during an incremental cycling test using surface electromyography (sEMG), can be sensitive to the different metabolic requests elicited by the exercise. In particular, the relationship between ventilatory threshold (T-vent), V(')O(2max) and MFCV was explored. Eleven male physically active subjects (age 30+/-9 years) undertook a 1-min incremental cycling test to exhaustion. T-vent and V(')O(2max) were measured using an open circuit breath by breath gas analyzer. The sEMG was recorded from the vastus lateralis muscle with an adhesive 4-electrodes array, and the MFCV was computed on each sEMG burst over the last 30-s of each step. The mean V(')O(2max) obtained during the maximal test was 53.32+/-2.33 ml kg(-1) min(-1), and the T-vent was reached at 80.77+/-3.49% of V(')O(2max). In all subjects reliable measures of MFCV were obtained at every exercise intensity (cross correlation values >0.8). MFCV increased linearly with the mechanical load, reaching a maximum value of 4.28+/-0.67 ms(-1) at an intensity corresponding to the T-vent. Thereafter, MFCV declined until maximal work intensities. This study demonstrates that MFCV can be used as non-invasive tool to infer MUs recruitment/derecruitment strategies even during dynamic exercise from low to maximal intensities.
authors.affiliation: Department of Human Movement and Sport Sciences, IUSM University of Rome Foro Italico, 00194 Rome, Italy. paola.sbriccoli@iusm.it
authors.forename: Paola
authors.initials: P
authors.lastname: Sbriccoli
authors.forename: Massimo
authors.initials: M
authors.lastname: Sacchetti
authors.forename: Francesco
authors.initials: F
authors.lastname: Felici
authors.forename: Leonardo
authors.initials: L
authors.lastname: Gizzi
authors.forename: Mauro
authors.initials: M
authors.lastname: Lenti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Scotto
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Vito
mesh_terms: D015308:Anaerobic Threshold / Q000502:physiology*; D004576:Electromyography / Q000379:methods*; D005080:Exercise Test / Q000379:methods; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*