Abstract
Purpose
When exercising above the lactic threshold (LT), the slow component of oxygen uptake (\(\dot{V}{\text{O}}_{{{\text{2sc}}}}\)) 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 (\(\dot{V}{\text{O}}_{{2}}\)) 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 (\(\dot{V}{\text{O}}_{{{\text{2net}}}}\)) 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
\(\dot{V}{\text{O}}_{{{\text{2net}}}}\) after the third minute in FB-Torque increased with time (\(\dot{V}{\text{O}}_{{{\text{2net}}}}\) = 94 × t + 564; R2 = 0.99; P = 0.001), but not during FB-EMG. \(\dot{V}{\text{O}}_{{{\text{2net}}}}\)/T increased only during FB-Torque (\(\dot{V}{\text{O}}_{{{\text{2net}}}}\)/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 \(\dot{V}{\text{O}}_{{{\text{2sc}}}}\).
Conclusion
The analysis of the RMS, \(\dot{V}{\text{O}}_{{2}}\) and T during FB-Torque suggests that the intrinsic mechanism attributable to the decay of contraction efficiency was responsible for an increase of \(\dot{V}{\text{O}}_{{{\text{2net}}}}\) equal to 18% of the total \(\dot{V}{\text{O}}_{{{\text{2sc}}}}\).
Similar content being viewed by others
Data availability
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.
Abbreviations
- [Cr]:
-
Free creatine concentration
- EMGon :
-
Onset of the sEMG signal during contraction
- EMGoff :
-
Offset of the sEMG signal during contraction
- FB-EMG:
-
Test performed maintaining the muscular activation constant
- FB-Torque:
-
Test performed maintaining the muscular strength constant
- F on :
-
Time of onset of strength signal during contraction
- F off :
-
Time of offset of strength signal during contraction
- iEMG:
-
Integrated sEMG
- [La]m :
-
Muscle lactate concentration
- [La]b :
-
Blood lactate concentration
- LT:
-
Lactic threshold
- MF:
-
Median frequency of sEMG
- MUs:
-
Motor units
- MVC:
-
Maximal voluntary contraction
- MVCpre:
-
Preliminary MVC test
- MVCpost:
-
Final MVC test
- RMS:
-
Root mean square
- sEMG:
-
Surface electromyography
- T :
-
Torque
- VL:
-
Vastus lateralis muscle
- \(\dot{V\mathrm{C}}\)O2 :
-
Carbon dioxide production
- \(\dot{V}\) E :
-
Minute pulmonary ventilation \(\dot{V}\)O2max: maximal oxygen uptake
- \(\dot{V}\)O2net :
-
Net oxygen uptake
- \(\dot{V}\)O2rm :
-
Oxygen consumption due to the work of the respiratory muscles
- \(\dot{V}\)O2sc :
-
Slow component of oxygen uptake
- \(\dot{V}\)O2ss :
-
Oxygen uptake at steady state
- \(\dot{V}\)O2net/T:
-
The ratio between net oxygen uptake and torque
- \(\dot{V}\)O2net/RMS:
-
The ratio between net oxygen uptake and RMS
References
Barstow TJ, Jones AM, Nguyen PH, Casaburi R (1996) Influence of muscle fiber type and pedal frequency on the oxygen uptake kinetics of heavy exercise. J Appl Physiol 81:1642–1650
Cannon DT, Kolkhorst FW, Cipriani DJ (2007) Electromyographic data do not support progressive recruitment of muscle fibers during exercise exhibiting a V O2 slow component. J Physiol Anthropol 26:541–546
Cannon DT, White AC, Andriano MF, Kolkhorst FW, Rossiter HB (2011) Skeletal muscle fatigue precedes the slow component of oxygen uptake kinetics during exercise in humans. J Physiol 589:727–739
Capelli C, Antonutto G, Zamparo P, Girardis M, di Prampero PE (1993) Effects of prolonged cycle ergometer exercise on maximal muscle power and oxygen uptake in humans. Eur J Appl Physiol 66:189–195
Cheng AJ, Place N, Westerblad H (2017) Molecular basis for exercise-induced fatigue: the importance of strictly controlled cellular Ca2+ handling. In: Zierath JR, Joyner MJ, Hawley JA (eds) The biology of exercise. Cold Spring Harbor Laboratory press, New York, pp 169–199
Coast JR, Rasmussen SA, Krause KM, O’Kroy JA, Rhodes J (1993) Ventilatory work and oxygen consumption during exercise and hyperventilation. J Appl Physiol 74:793–798
D’Agostino RB (1986) Tests for normal distribution. In: D’Agostino RB, Stepenes MA (eds) Goodness-of-fit techniques. Macel Decker, New York, p 1986
di Prampero PE (1981) Energetics of muscular exercise. Rev Physiol Biochem Pharmacol 89:143–222
Gandevia SC (2001) Spinal and supraspinal factors in human muscle fatigue. Physiol Rev 81:1725–1789
Gandevia SC, Allen GM, Butler JE, Taylor J (1996) Supraspinal factors in human muscle fatigue: evidence for suboptimal output from the motor cortex. J Physiol 490:529–536
Grassi B, Rossiter HB, Zoladz JA (2015) Skeletal muscle fatigue and decreased efficiency: two sides of the same coin? Exerc Sport Sci Rev 43:75–83
Hunter SK (2017) Performance fatigability: mechanisms and task specificity. In: Zierath JR, Joyner MJ, Hawley JA (eds) The biology of exercise. Cold Spring Harbor Laboratory press, New York, pp 200–225
Li X, Zhou P, Aruin AS (2007) Teager-Kaiser energy operation of surface EMG improves muscle activity onset detection. Ann Biomed Eng 35:1532–1538. https://doi.org/10.1007/s10439-007-9320-z
Mahler M (1985) First-order kinetics of muscle oxygen consumption and an equivalent proportionality between QO2 and phosphorylcreatine leve. J Gen Physiol 30:135–165
Poole DC, Jones AM (2012) Oxygen uptake kinetics. Compar Physiol 2:933–996
Poole DC, Ward SA, Gardner GW, Whipp BJ (1988) Metabolic and respiratory profile of the upper limit for prolonged exercise in man. Ergonomics 31(9):1265–1279. https://doi.org/10.1080/00140138808966766. (PMID: 3191904)
Poole DC, Schaffartzik W, Knight DR, Derion T, Kennedy B, Guy HJ, Prediletto R, Wagner PD (1991) Contribution of excising legs to the slow component of oxygen uptake kinetics in humans. J Appl Physiol 71:1245–1260
Rowell LB (1993) Cardiovascular adjustments to isometric contractions. Human cardiovascular control. Oxford University Press, Oxford, pp 302–325
Scheuermann BW, Hoelting BD, Larry Noble ML, Barstow TJ (2001) The slow component of O2 uptake is not accompanied by changes in muscle EMG during repeated bouts of heavy exercise in humans. J Physiol 531:245–256
SENIAM (2021) Recommendations for sensor locations in lower leg or foot muscles. http://www.seniam.org. Accessed 1 Oct 2021.
Shinohara M, Moritani T (1992) Increase in neuromuscular activity and oxygen uptake during heavy exercise. Ann Physiol Anthropol 11:257–262
Solnik S, Rider P, Steinweg K, DeVita P, Hortobágyi T (2010) Teager-Kaiser energy operator signal conditioning improves EMG onset detection. Eur J Appl Physiol 110:489–498. https://doi.org/10.1007/s00421-010-1521-8
Stienen GJ, Kiers JL, Bottinelli R, Reggiani C (1996) Myofibrillar ATPase activity in skinned human skeletal muscle fibres: fibre type and temperature dependence. J Physiol 493:299–307
Tonkonogi M, Sahlin K (2002) Physical exercise and mitochondrial function in human skeletal muscle. Exer Sports Sci Rev 30:129–137
Willis WT, Jackman MR (1994) Mitochondrial function during heavy exercise. Med Sci Sports Exerc 26:1347–1353
Zar JH (2010) Biostatistical analysis, 5th edn. Pearson, Upper Saddle River, pp 363–378
Zoladz J, Korzeniewski B (2001) Physiological background of the change point in V O2 and the slow component of oxygen uptake kinetics. J Physiol Pharmacol 52:167–184
Zoladz J, Gladden LB, Hogan MC, Nieckarz Z, Grassi B (2008) Progressive recruitment of muscle fibers is not necessary for the slow component of V ̇O2 kinetics. J Appl Physiol 105:575–580
Acknowledgements
The authors heartily thank the volunteers who accepted to participate in the study.
Funding
The study was funded by the funds for basic research allocated to the investigators by the Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona.
Author information
Authors and Affiliations
Contributions
ET, CC, and MB: conception and design of the experiment; MB, ET, MN: data collection; MB, MN; ET, CC: analysis of data; CC; ET; MB: interpretation of the data; MB, ET, CC: writing the first draft. All authors—revising the manuscript. All authors read and approved the final version of the manuscript.
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
Communicated by Guido Ferretti.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Tam, E., Nardon, M., Bertucco, M. et al. The mechanisms underpinning the slow component of \(\dot{V}{\text{O}}_{{2}}\) in humans. Eur J Appl Physiol 124, 861–872 (2024). https://doi.org/10.1007/s00421-023-05315-z
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00421-023-05315-z