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Aerobic fitness, muscle efficiency, and motor unit recruitment during ramp exercise

Jan Boone (UGent) , Katrien Koppo (UGent) , Thomas Barstow and Jacques Bouckaert (UGent)
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Abstract
Purpose: The purpose of this study was to test whether the higher slope of the oxygen uptake/work rate relationship (Delta(V) over dotO(2)/Delta W) in aerobically trained subjects compared with less trained counterparts during a ramp protocol is related to changes in muscle fiber activation. Methods: Ten cyclists and 10 physically active (PA) students performed two ramp exercises (ramp 25 protocol and relative ramp protocol, leading to exhaustion in 12 min) and a step protocol (20-60-100-140-180-220 W). Pulmonary gas exchange was measured, and muscle fiber activity was recorded with surface EMG of the musculus vastus lateralis. (V) over dot O-2 and integrated EMG (iEMG) were described as functions of work rate up to the gas exchange threshold, and linear regression analysis was used to determine the Delta(V) over dotO(2)/Delta W and the slope of the iEMG/W relationship (Delta iEMG/Delta W). Results: The statistical analysis revealed a higher Delta(V) over dotO(2)/Delta W in cyclists compared with PA students in ramp exercises (ramp 25 = 9.98 +/- 0.51 vs 9.18 +/- 0.59 mL.min(-1).W-1; relative ramp = 9.87 +/- 0.30 vs 9.16 +/- 0.33 mL.min(-1).W-1 in the cyclists and PA students, respectively; P < 0.05) but not in step exercise (9.97 +/- 0.32 and 9.83 +/- 0.37 mL.min(-1).W-1 in cyclists and PA students, respectively; P > 0.05). In addition, cyclists demonstrated a higher Delta iEMG/Delta W in ramp exercises (0.96 +/- 0.14%.W-1 and 0.98 +/- 0.14%.W-1 in ramp 25 and relative ramp, respectively) compared with step exercise (0.75 +/- 0.12%.W-1, P < 0.05), whereas in the PA students, Delta iEMG/Delta W did not differ between the ramp protocol (0.75 +/- 0.10%.W-1 and 0.70 +/- 0.12%.W-1 in ramp 25 and relative ramp, respectively) and the step protocol (0.77 +/- 0.17%.W-1, P > 0.05). Conclusions: The present study reveals that trained cyclists demonstrate reduced mechanical efficiency in the ramp protocol and that this phenomenon is associated with an "overactivation" of muscle fibers.
Keywords
FIBER TYPE, HIGH-POWER OUTPUTS, WORK RATE INCREMENT, MODERATE-INTENSITY EXERCISE, VO2-POWER OUTPUT RELATIONSHIP, CHRONIC HEART-FAILURE, OXYGEN-UPTAKE KINETICS, MUSCLE FIBER, CYCLING, SURFACE EMG, OXYGEN UPTAKE, CYCLING EFFICIENCY, HUMANS, VO2

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Chicago
Boone, Jan, Katrien Koppo, Thomas Barstow, and Jacques Bouckaert. 2010. “Aerobic Fitness, Muscle Efficiency, and Motor Unit Recruitment During Ramp Exercise.” Medicine and Science in Sports and Exercise 42 (2): 402–408.
APA
Boone, Jan, Koppo, K., Barstow, T., & Bouckaert, J. (2010). Aerobic fitness, muscle efficiency, and motor unit recruitment during ramp exercise. MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 42(2), 402–408.
Vancouver
1.
Boone J, Koppo K, Barstow T, Bouckaert J. Aerobic fitness, muscle efficiency, and motor unit recruitment during ramp exercise. MEDICINE AND SCIENCE IN SPORTS AND EXERCISE. 2010;42(2):402–8.
MLA
Boone, Jan, Katrien Koppo, Thomas Barstow, et al. “Aerobic Fitness, Muscle Efficiency, and Motor Unit Recruitment During Ramp Exercise.” MEDICINE AND SCIENCE IN SPORTS AND EXERCISE 42.2 (2010): 402–408. Print.
@article{949369,
  abstract     = {Purpose: The purpose of this study was to test whether the higher slope of the oxygen uptake/work rate relationship (Delta(V) over dotO(2)/Delta W) in aerobically trained subjects compared with less trained counterparts during a ramp protocol is related to changes in muscle fiber activation. Methods: Ten cyclists and 10 physically active (PA) students performed two ramp exercises (ramp 25 protocol and relative ramp protocol, leading to exhaustion in 12 min) and a step protocol (20-60-100-140-180-220 W). Pulmonary gas exchange was measured, and muscle fiber activity was recorded with surface EMG of the musculus vastus lateralis. (V) over dot O-2 and integrated EMG (iEMG) were described as functions of work rate up to the gas exchange threshold, and linear regression analysis was used to determine the Delta(V) over dotO(2)/Delta W and the slope of the iEMG/W relationship (Delta iEMG/Delta W). Results: The statistical analysis revealed a higher Delta(V) over dotO(2)/Delta W in cyclists compared with PA students in ramp exercises (ramp 25 = 9.98 +/- 0.51 vs 9.18 +/- 0.59 mL.min(-1).W-1; relative ramp = 9.87 +/- 0.30 vs 9.16 +/- 0.33 mL.min(-1).W-1 in the cyclists and PA students, respectively; P {\textlangle} 0.05) but not in step exercise (9.97 +/- 0.32 and 9.83 +/- 0.37 mL.min(-1).W-1 in cyclists and PA students, respectively; P {\textrangle} 0.05). In addition, cyclists demonstrated a higher Delta iEMG/Delta W in ramp exercises (0.96 +/- 0.14\%.W-1 and 0.98 +/- 0.14\%.W-1 in ramp 25 and relative ramp, respectively) compared with step exercise (0.75 +/- 0.12\%.W-1, P {\textlangle} 0.05), whereas in the PA students, Delta iEMG/Delta W did not differ between the ramp protocol (0.75 +/- 0.10\%.W-1 and 0.70 +/- 0.12\%.W-1 in ramp 25 and relative ramp, respectively) and the step protocol (0.77 +/- 0.17\%.W-1, P {\textrangle} 0.05). Conclusions: The present study reveals that trained cyclists demonstrate reduced mechanical efficiency in the ramp protocol and that this phenomenon is associated with an {\textacutedbl}overactivation{\textacutedbl} of muscle fibers.},
  author       = {Boone, Jan and Koppo, Katrien and Barstow, Thomas and Bouckaert, Jacques},
  issn         = {0195-9131},
  journal      = {MEDICINE AND SCIENCE IN SPORTS AND EXERCISE},
  keyword      = {FIBER TYPE,HIGH-POWER OUTPUTS,WORK RATE INCREMENT,MODERATE-INTENSITY EXERCISE,VO2-POWER OUTPUT RELATIONSHIP,CHRONIC HEART-FAILURE,OXYGEN-UPTAKE KINETICS,MUSCLE FIBER,CYCLING,SURFACE EMG,OXYGEN UPTAKE,CYCLING EFFICIENCY,HUMANS,VO2},
  language     = {eng},
  number       = {2},
  pages        = {402--408},
  title        = {Aerobic fitness, muscle efficiency, and motor unit recruitment during ramp exercise},
  url          = {http://dx.doi.org/10.1249/MSS.0b013e3181b0f2e2},
  volume       = {42},
  year         = {2010},
}

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