The mechanisms underpinning the slow component of [Formula: see text] in humans.
Eur J Appl Physiol
; 124(3): 861-872, 2024 Mar.
Article
em En
| MEDLINE
| ID: mdl-37775591
ABSTRACT
PURPOSE:
When exercising above the lactic threshold (LT), the slow component of oxygen uptake ([Formula see text]) appears, mainly ascribed to the progressive recruitment of Type II fibers. However, also the progressive decay of the economy of contraction may contribute to it. We investigated oxygen uptake ([Formula see text]) during isometric contractions clamping torque (T) or muscular activation to quantify the contributions of the two mechanisms.METHODS:
We assessed for 7 min T of the leg extensors, net oxygen uptake ([Formula see text]) and root mean square (RMS) from vastus lateralis (VL) in 11 volunteers (21 ± 2 yy; 1.73 ± 0.11 m; 67 ± 14 kg) during cyclic isometric contractions (contraction/relaxation 5 s/5 s) (i) at 65% of maximal voluntary contraction (MVC) (FB-Torque) and; (ii) keeping the level of RMS equal to that at 65% of MVC (FB-EMG).RESULTS:
[Formula see text] after the third minute in FB-Torque increased with time ([Formula see text] = 94 × t + 564; R2 = 0.99; P = 0.001), but not during FB-EMG. [Formula see text]/T increased only during FB-Torque ([Formula see text]/T = 1.10 × t + 0.57; R2 = 0.99; P = 0.001). RMS was larger in FB-Torque than in FB-EMG and significantly increased in the first three minutes of exercise to stabilize till the end of the trial, indicating that the pool of recruited MUs remained constant despite [Formula see text].CONCLUSION:
The analysis of the RMS, [Formula see text] and T during FB-Torque suggests that the intrinsic mechanism attributable to the decay of contraction efficiency was responsible for an increase of [Formula see text] equal to 18% of the total [Formula see text].Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Músculo Esquelético
/
Contração Isométrica
Limite:
Humans
Idioma:
En
Revista:
Eur J Appl Physiol
Assunto da revista:
FISIOLOGIA
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Itália