Effects of strength training on muscle fatigue mapping from surface EMG and blood metabolites.
OBJECTIVE
this study examined the effects of heavy resistance training on the relationships between power loss and surface EMG (sEMG) indices and blood metabolite concentrations on dynamic exercise-induced fatigue with the same relative load as in pretraining.


METHODS
twelve trained subjects performed five sets consisting of 10 repetitions in the leg press, with 2 min of rest between sets before and after a strength training period. sEMG variables (the mean average voltage, the median spectral frequency, and the Dimitrov spectral index of muscle fatigue) from vastus medialis and lateralis muscles and metabolic responses (i.e., blood lactate, uric acid, and ammonia concentrations) were measured.


RESULTS
the peak power loss after the posttraining protocol was greater (61%) than the decline observed in the pretraining protocol (46%). Similar sEMG changes were found for both protocols, whereas higher metabolic demand was observed during the posttraining exercise. The linear models on the basis of the relations found between power loss and changes in sEMG variables were significantly different between pretraining and posttraining, whereas the linear models on the basis of the relations between power loss and changes in blood metabolite concentrations were similar.


CONCLUSIONS
linear models that use blood metabolites to map acute exercise-induced peak power changes were more accurate in detecting these changes before and after a short-term training period, whereas an attempt to track peak power loss using sEMG variables may fail after a strength training period.
Izquierdo
Mikel
M
Studies, Research and Sport Medicine Center, Government of Navarra, Pamplona, Navarra, SPAIN. izquierdo@gmail.com
González-Izal
Miriam
M
Navarro-Amezqueta
Ion
I
Calbet
Jose A L
JA
Ibañez
Javier
J
Malanda
Armando
A
Mallor
Fermin
F
Häkkinen
Keijo
K
Kraemer
William J
WJ
Gorostiaga
Esteban M
EM
D000328:Adult; D000641:Ammonia / Q000097:blood; D004576:Electromyography; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*; D014527:Uric Acid / Q000097:blood
D014527:Uric Acid; D019344:Lactic Acid; D000641:Ammonia