Is the V˙o 2 slow component dependent on progressive recruitment of fast-twitch fibers in trained runners?

2001 ◽  
Vol 90 (6) ◽  
pp. 2212-2220 ◽  
Author(s):  
F. Borrani ◽  
R. Candau ◽  
G. Y. Millet ◽  
S. Perrey ◽  
J. Fuchslocher ◽  
...  
Keyword(s):  
Slow Component ◽  
Vastus Lateralis ◽  
Classical Model ◽  
Average Frequency ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Lower Limb Muscles ◽  
Motor Unit Discharge ◽  
Gastrocnemius Muscles ◽  
Fast Twitch

The goal of this study was to use spectral analysis of EMG data to test the hypothesis that the O2 uptake (V˙o 2) slow component is due to a recruitment of fast fibers. Thirteen runners carried out a treadmill test with a constant speed, corresponding to 95% of the velocity associated with maximal V˙o 2. TheV˙o 2 response was fit with the classical model including three exponential functions. Electrical activity of six lower limb muscles (vastus lateralis, soleus, and gastrocnemius of both sides) was measured using electromyogram surface electrodes. Mean power frequency (MPF) was used to study the kinetics of the electromyogram discharge frequency. Three main results were observed: 1) a common pattern of the MPF kinetics in the six muscles studied was noted; 2) MPF decreased in the first part of the exercise, followed by an increase for all the muscles studied, but only the vastus lateralis, and gastrocnemius muscles of both sides increased significantly ( P < 0.05); and 3) the beginning of the MPF increase of the four muscles mentioned above corresponded with the beginning of the slow component. Our results suggest a progression in the average frequency of the motor unit discharge toward the high frequencies, which coheres with the hypothesis of the progressive recruitment of fast-twitch fibers during the V˙o 2 slow component. However, this interpretation must be taken with caution because MPF is the result of a balance between several phenomena.

scholarly journals Effects of prior heavy exercise onV˙o 2 kinetics during heavy exercise are related to changes in muscle activity

2002 ◽  
Vol 93 (1) ◽  
pp. 167-174 ◽  
Author(s):  
Mark Burnley ◽  
Jonathan H. Doust ◽  
Derek Ball ◽  
Andrew M. Jones
Keyword(s):  
Slow Component ◽  
Vastus Lateralis ◽  
Gluteus Maximus ◽  
Exercise Bout ◽  
Motor Units ◽  
Primary Response ◽  
Heavy Exercise ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Leg Cycling

We hypothesized that the elevated primary O2 uptake (V˙o 2) amplitude during the second of two bouts of heavy cycle exercise would be accompanied by an increase in the integrated electromyogram (iEMG) measured from three leg muscles (gluteus maximus, vastus lateralis, and vastus medialis). Eight healthy men performed two 6-min bouts of heavy leg cycling (at 70% of the difference between the lactate threshold and peakV˙o 2) separated by 12 min of recovery. The iEMG was measured throughout each exercise bout. The amplitude of the primary V˙o 2 response was increased after prior heavy leg exercise (from mean ± SE 2.11 ± 0.12 to 2.44 ± 0.10 l/min, P < 0.05) with no change in the time constant of the primary response (from 21.7 ± 2.3 to 25.2 ± 3.3 s), and the amplitude of theV˙o 2 slow component was reduced (from 0.79 ± 0.08 to 0.40 ± 0.08 l/min, P < 0.05). The elevated primary V˙o 2 amplitude after leg cycling was accompanied by a 19% increase in the averaged iEMG of the three muscles in the first 2 min of exercise (491 ± 108 vs. 604 ± 151% increase above baseline values, P < 0.05), whereas mean power frequency was unchanged (80.1 ± 0.9 vs. 80.6 ± 1.0 Hz). The results of the present study indicate that the increased primaryV˙o 2 amplitude observed during the second of two bouts of heavy exercise is related to a greater recruitment of motor units at the onset of exercise.

scholarly journals Inter- and Intra-Individual Differences in EMG and MMG during Maximal, Bilateral, Dynamic Leg Extensions

Sports ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 175 ◽  
Author(s):  
John Paul V. Anders ◽  
Cory M. Smith ◽  
Joshua L. Keller ◽  
Ethan C. Hill ◽  
Terry J. Housh ◽  
...  
Keyword(s):  
Individual Differences ◽  
Repeated Measures ◽  
Polynomial Regression ◽  
Vastus Lateralis ◽  
Regression Analyses ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Leg Extension ◽  
Neuromuscular Responses ◽  
Muscle Actions

The purpose of this study was to compare the composite, inter-individual, and intra-individual differences in the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during fatiguing, maximal, bilateral, and isokinetic leg extension muscle actions. Thirteen recreationally active men (age = 21.7 ± 2.6 years; body mass = 79.8 ± 11.5 kg; height = 174.2 ± 12.7 cm) performed maximal, bilateral leg extensions at 180°·s−1 until the torque values dropped to 50% of peak torque for two consecutive repetitions. The EMG and MMG signals from the vastus lateralis (VL) muscles of both limbs were recorded. Four 2(Leg) × 19(time) repeated measures ANOVAs were conducted to examine mean differences for EMG AMP, EMG MPF, MMG AMP, and MMG MPF between limbs, and polynomial regression analyses were performed to identify the patterns of neuromuscular responses. The results indicated no significant differences between limbs for EMG AMP (p = 0.44), EMG MPF (p = 0.33), MMG AMP (p = 0.89), or MMG MPF (p = 0.52). Polynomial regression analyses demonstrated substantial inter-individual variability. Inferences made regarding the patterns of neuromuscular responses to fatiguing and bilateral muscle actions should be considered on a subject-by-subject basis.

Interlimb Neuromuscular Responses During Fatiguing, Bilateral, Leg Extension Exercise at a Moderate Versus High Load

Motor Control ◽  
2021 ◽  
Vol 25 (1) ◽  
pp. 59-74
Author(s):  
Taylor K. Dinyer ◽  
Pasquale J. Succi ◽  
M. Travis Byrd ◽  
Caleb C. Voskuil ◽  
Evangeline P. Soucie ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
High Load ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Leg Extension ◽  
Neuromuscular Responses ◽  
Power Frequency ◽  
The Central Nervous System ◽  
Common Drive ◽  
Repetitions To Failure

This study determined the load- and limb-dependent neuromuscular responses to fatiguing, bilateral, leg extension exercise performed at a moderate (50% one-repetition maximum [1RM]) and high load (80% 1RM). Twelve subjects completed 1RM testing for the bilateral leg extension, followed by repetitions to failure at 50% and 80% 1RM, on separate days. During all visits, the electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) signals were recorded from the vastus lateralis of both limbs. There were no limb-dependent responses for any of the neuromuscular signals and no load-dependent responses for EMG AMP, MMG AMP, or MMG MPF (p = .301–.757), but there were main effects for time that indicated increases in EMG and MMG AMP and decreases in MMG MPF. There was a load-dependent decrease in EMG MPF over time (p = .032) that suggested variability in the mechanism responsible for metabolite accumulation at moderate versus high loads. These findings suggested that common drive from the central nervous system was used to modulate force during bilateral leg extension performed at moderate and high loads.

scholarly journals Comparative Study of Kinematics and Muscle Activity Between Elite and Amateur Table Tennis Players During Topspin Loop Against Backspin Movements

2018 ◽  
Vol 64 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Meizi Wang ◽  
Lin Fu ◽  
Yaodong Gu ◽  
Qichang Mei ◽  
Fengqin Fu ◽  
...  
Keyword(s):  
Lower Limb ◽  
Muscle Activity ◽  
Rectus Femoris ◽  
Surface Emg ◽  
Table Tennis ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Lower Limb Muscles ◽  
Balance Ability ◽  
Hip Flexion

Abstract This study investigated differences of lower limb kinematics and muscle activity during table tennis topspin loop against backspin movements between elite players (EPs) and amateur players (APs). Ten EPs and ten APs performed crosscourt backhand loop movements against the backspin ball with maximal power. Vicon motion analysis and a MEGA ME6000 system was used to capture kinematics and surface EMG data. The motion was divided into two phases, including the backswing and swing. The joints’ flexion and extension angle tendency between EPs and APs differed significantly. The coefficient of multiple correlation (CMC) values for EPs were all beyond 0.9, indicating high similarity of joint angles change. APs presented moderate similarity with CMC values from 0.5 to 0.75. Compared to APs, EPs presented larger ankle eversion, knee and hip flexion at the beginning moment of the backswing. In the sEMG test, EPs presented smaller standardized AEMG (average electromyography) of the lower limb muscles in the rectus femoris and tibia anterior on both sides. Additionally, the maximum activation of each muscle for EPs was smaller and MPF (mean power frequency) of the lower limb was greater during the whole movement. The present study revealed that EPs could complete this technical motion more economically than APs, meanwhile, EPs were more efficient in muscle usage and showed better balance ability.

Autoradiographic delineation of skeletal muscle alpha 1-adrenergic receptor distribution

1990 ◽  
Vol 259 (5) ◽  
pp. H1402-H1408 ◽  
Author(s):  
W. H. Martin ◽  
T. K. Tolley ◽  
J. E. Saffitz
Keyword(s):  
Blood Vessels ◽  
Cross Sections ◽  
Specific Binding ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Type I ◽  
Receptor Density ◽  
Autoradiographic Analysis ◽  
Gastrocnemius Muscles ◽  
Fast Twitch

We used light microscopic autoradiography to quantify the distribution of alpha 1-adrenergic receptors in vessels and muscle fibers of slow-twitch (type I), fast-twitch (types IIa and IIb), and mixed fiber muscles of the rat hindquarter. Frozen cross sections of soleus, vastus lateralis, and gastrocnemius muscles were incubated under equilibrium binding conditions with 10-200 pM [3H]prazosin with or without 10(-5) M phentolamine. Because of the low concentration of bound radioligand, specific binding could not be detected with scintillation spectrometry in whole tissue sections scraped from slides. However, quantitative autoradiographic analysis after extended intervals of emulsion exposure revealed a low but significant level of specific binding in muscle fibers. No difference in alpha 1-receptor density was observed among types I, IIa, and IIb fibers. Small blood vessels had a much greater alpha 1-receptor density than muscle fibers. Resistance arterioles (20-100 microns diam) and small arteries (100-500 microns diam) contained 5.8 +/- 0.9 and 31.6 +/- 7.6 (+/- SE) times more binding sites per unit section area, respectively, than did surrounding muscle fibers (both P less than 0.001). Ratios of specific grain densities in fibers and blood vessels did not vary with radioligand concentration, indicating that observed grain densities reflected differences in receptor concentration rather than radioligand affinity by fiber and vessel receptors. The densities of vascular alpha 1-receptors did not vary in slow- and fast-twitch muscles, but resistance arterioles were six and eight times more numerous in soleus than in gastrocnemius and vastus muscles, respectively (both P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of oxygen uptake kinetics during concentric and eccentric cycle exercise

2001 ◽  
Vol 91 (5) ◽  
pp. 2135-2142 ◽  
Author(s):  
S. Perrey ◽  
A. Betik ◽  
R. Candau ◽  
J. D. Rouillon ◽  
R. L. Hughson
Keyword(s):  
High Intensity ◽  
Slow Component ◽  
Rectus Femoris ◽  
Work Rate ◽  
Vastus Medialis ◽  
Metabolic Demand ◽  
Mean Power ◽  
Mean Power Frequency ◽  
Power Frequency ◽  
Integrated Emg

O2 uptake (V˙o 2) kinetics and electromyographic (EMG) activity from the vastus medialis, rectus femoris, biceps femoris, and medial gastrocnemius muscles were studied during constant-load concentric and eccentric cycling. Six healthy men performed transitions from baseline to high-intensity eccentric (HE) exercise and to high-intensity (HC), moderate-intensity (MC), and low-intensity (LC) concentric exercise. For HE and HC exercise, absolute work rate was equivalent. For HE and LC exercise,V˙o 2 was equivalent.V˙o 2 data were fit by a two- or three-component exponential model. Surface EMG was recorded during the last 12 s of each minute of exercise to obtain integrated EMG and mean power frequency. Only in the HC exercise didV˙o 2 increase progressively with evidence of a slow component ( phase 3), and only in HC exercise was there evidence of a coincident increase with time in integrated EMG of the vastus medialis and rectus femoris muscles ( P < 0.05) with no change in mean power frequency. The phase 2time constant was slower in HC [24.0 ± 1.7 (SE) s] than in HE (14.7 ± 2.8 s) and LC (16.7 ± 2.2 s) exercise, while it was not different from MC exercise (20.6 ± 2.1 s). These results show that the rate of increase inV˙o 2 at the onset of exercise was not different between HE and LC exercise, where the metabolic demand was similar, but both had significantly faster kinetics forV˙o 2 than HC exercise. TheV˙o 2 slow component might be related to increased muscle activation, which is a function of metabolic demand and not absolute work rate.

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