Muscle fiber recruitment and the slow component of O2 uptake: constant work rate vs. all-out sprint exercise

2011 ◽  
Vol 300 (3) ◽  
pp. R700-R707 ◽  
Author(s):  
Anni Vanhatalo ◽  
David C. Poole ◽  
Fred J. DiMenna ◽  
Stephen J. Bailey ◽  
Andrew M. Jones
Keyword(s):  
Muscle Activation ◽  
Slow Component ◽  
Vastus Lateralis ◽  
Experimental Tests ◽  
Work Rate ◽  
Voluntary Exercise ◽  
Vastus Lateralis Muscle ◽  
Incremental Test ◽  
Constant Work Rate ◽  
Integrated Emg

The slow component of pulmonary O2 uptake (V̇o2) during constant work rate (CWR) high-intensity exercise has been attributed to the progressive recruitment of (type II) muscle fibers. We tested the following hypotheses: 1) the V̇o2 slow component gain would be greater in a 3-min all-out cycle test than in a work-matched CWR test, and 2) the all-out test would be associated with a progressive decline, and the CWR test with a progressive increase, in muscle activation, as estimated from the electromyogram (EMG) of the vastus lateralis muscle. Eight men (aged 21–39 yr) completed a ramp incremental test, a 3-min all-out test, and a work- and time-matched CWR test to exhaustion. The maximum V̇o2 attained in an initial ramp incremental test (3.97 ± 0.83 l/min) was reached in both experimental tests (3.99 ± 0.84 and 4.03 ± 0.76 l/min for all-out and CWR, respectively). The V̇o2 slow component was greater ( P < 0.05) in the all-out test (1.21 ± 0.31 l/min, 4.2 ± 2.2 ml·min−1·W−1) than in the CWR test (0.59 ± 0.22 l/min, 1.70 ± 0.5 ml·min−1·W−1). The integrated EMG declined by 26% ( P < 0.001) during the all-out test and increased by 60% ( P < 0.05) during the CWR test from the first 30 s to the last 30 s of exercise. The considerable reduction in muscle efficiency in the all-out test in the face of a progressively falling integrated EMG indicates that progressive fiber recruitment is not requisite for development of the V̇o2 slow component during voluntary exercise in humans.

scholarly journals A Rapidly-Incremented Tethered-Swimming Test for Defining Domain-Specific Training Zones

2017 ◽  
Vol 57 (1) ◽  
pp. 117-128
Author(s):  
Dalton M. Pessôa Filho ◽  
Leandro O.C. Siqueira ◽  
Astor R. Simionato ◽  
Mário A.C. Espada ◽  
Daniel S. Pestana ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Work Rate ◽  
Metabolic Rates ◽  
Incremental Test ◽  
Domain Specific ◽  
Respiratory Compensation ◽  
Exercise Economy ◽  
Constant Work Rate ◽  
Swimming Test ◽  
Gas Exchange Threshold

AbstractThe purpose of this study was to investigate whether a tethered-swimming incremental test comprising small increases in resistive force applied every 60 seconds could delineate the isocapnic region during rapidly-incremented exercise. Sixteen competitive swimmers (male, n = 11; female, n = 5) performed: (a) a test to determine highest force during 30 seconds of all-out tethered swimming (Favg) and the ΔF, which represented the difference between Favg and the force required to maintain body alignment (Fbase), and (b) an incremental test beginning with 60 seconds of tethered swimming against a load that exceeded Fbase by 30% of ΔF followed by increments of 5% of ΔF every 60 seconds. This incremental test was continued until the limit of tolerance with pulmonary gas exchange (rates of oxygen uptake and carbon dioxide production) and ventilatory (rate of minute ventilation) data collected breath by breath. These data were subsequently analyzed to determine whether two breakpoints defining the isocapnic region (i.e., gas exchange threshold and respiratory compensation point) were present. We also determined the peak rate of O2 uptake and exercise economy during the incremental test. The gas exchange threshold and respiratory compensation point were observed for each test such that the associated metabolic rates, which bound the heavy-intensity domain during constant-work-rate exercise, could be determined. Significant correlations (Spearman’s) were observed for exercise economy along with (a) peak rate of oxygen uptake (ρ = .562; p < 0.025), and (b) metabolic rate at gas exchange threshold (ρ = −.759; p < 0.005). A rapidly-incremented tethered-swimming test allows for determination of the metabolic rates that define zones for domain-specific constant-work-rate training.

Intent-Related Differences in Surface EMG of Maximum Eccentric and Concentric Contractions

2003 ◽  
Vol 19 (2) ◽  
pp. 99-105 ◽  
Author(s):  
Mark D. Grabiner ◽  
Tammy M. Owings
Keyword(s):  
Muscle Activation ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Eccentric Contraction ◽  
Surface Emg ◽  
Vastus Lateralis Muscle ◽  
Concentric Contractions ◽  
Concentric Contraction ◽  
Contraction Condition ◽  
The Difference

For this study it was hypothesized that when participants intended to perform a maximum voluntary concentric (or eccentric) contraction but had an eccentric (or concentric) contraction imposed upon them, the initial EMG measured during the isometric phase preceding the onset of the dynamometer motion would reflect the intended contraction condition. The surface EMG of the vastus lateralis muscle was measured in 24 participants performing isokinetic concentric and eccentric maximum voluntary knee extensor contractions. The contractions were initiated from rest and from the same knee flexion angle and required the same level of external force to trigger the onset of dynamometer motion. Vastus lateralis EMG were quantified during the isometric phase preceding the onset of the dynamometer motion. When participants intended to perform a concentric contraction but had an eccentric contraction imposed upon them, the initial EMG resembled that of a concentric contraction. When they intended to perform an eccentric contraction but had a concentric contraction imposed upon them, the initial EMG resembled that of an eccentric contraction. Overall, the difference between concentric and eccentric contractions observed during the period of theinitialmuscle activation implies that descending signals include information that distinguishes between eccentric and concentric contractions.

Phosphorylase a in human skeletal muscle during exercise and electrical stimulation

1978 ◽  
Vol 45 (6) ◽  
pp. 852-857 ◽  
Author(s):  
P. D. Gollnick ◽  
J. Karlsson ◽  
K. Piehl ◽  
B. Saltin
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Human Skeletal Muscle ◽  
Vastus Lateralis ◽  
Muscular Activity ◽  
Voluntary Exercise ◽  
Vastus Lateralis Muscle ◽  
Minor Importance ◽  
Muscle Lactate ◽  
Needle Technique

Experiments were conducted to examine the conversions of phosphorylase b to phosphorylase a in human skeletal muscle during bicycle exercise or isometric contractions. Muscle biopsies were obtained from the vastus lateralis with the needle technique at rest and either during or immediately after activity and frozen in liquid nitrogen within 2--4 s. Total phosphorylase and phosphorylase a activities were differentiated by measurement in the presence and absence of AMP, respectively. At rest 8.5% of the total phosphorylase activity existed in the a form. Little or no change in the percent of phosphorylase in the a form occurred during voluntary dynamic or static muscular activity that produced muscle lactate concentrations in excess of 18 mmol.kg-1 wet muscle. Electrical stimulation of the vastus lateralis muscle also failed to produce an increase in the percentage of phosphorylase a. These data suggest that during exercise the conversion of phosphorylase to the a form is of minor importance. An increased activity of phosphorylase b due to changes in muscle concentrations of ATP, AMP, and inorganic phosphate may regulate glycogenolysis during voluntary exercise in man.

scholarly journals Blood flow occlusion-related O2 extraction “reserve” is present in different muscles of the quadriceps but greater in deeper regions after ramp-incremental test

2018 ◽  
Vol 125 (2) ◽  
pp. 313-319 ◽  
Author(s):  
Danilo Iannetta ◽  
Dai Okushima ◽  
Erin Calaine Inglis ◽  
Narihiko Kondo ◽  
Juan M Murias ◽  
...  
Keyword(s):  
Blood Flow ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Incremental Exercise ◽  
Vastus Lateralis Muscle ◽  
Incremental Test ◽  
Time Resolved ◽  
Blood Flow Occlusion ◽  
Flow Occlusion

It was recently demonstrated that an O2 extraction reserve, as assessed by the near-infrared spectroscopy (NIRS)-derived deoxygenation signal ([HHb]), exists in the superficial region of vastus lateralis (VL) muscle during an occlusion performed at the end of a ramp-incremental test. However, it is unknown whether this reserve is present and/or different in magnitude in other portions and depths of the quadriceps muscles. We tested the hypothesis that an O2 extraction reserve would exist in other regions of this muscle but is greater in deep compared with more superficial portions. Superficial (VL-s) and deep VL (VL-d) as well as superficial rectus femoris (RF-s) were monitored by a combination of low- and high-power time-resolved (TRS) NIRS. During the occlusion immediately post-ramp-incremental test there was a significant overshoot in the [HHb] signal ( P < 0.05). However, the magnitude of this increase was greater in VL-d (93.2 ± 42.9%) compared with VL-s (55.0 ± 19.6%) and RF-s (47.8 ± 14.0%) ( P < 0.05). The present study demonstrated that an O2 extraction reserve exists in different pools of active muscle fibers of the quadriceps at the end of a ramp exercise to exhaustion. The greater magnitude in the reserve observed in the deeper portion of VL, however, suggests that this portion of muscle may present a greater surplus of oxygenated blood, which is likely due to a greater population of slow-twitch fibers. These findings add to the notion that the plateau in the [HHb] signal toward the end of a ramp-incremental exercise does not indicate the upper limit of O2 extraction. NEW & NOTEWORTHY Different portions of the quadriceps muscles exhibited an untapped O2 extraction reserve during a blood flow occlusion performed at the end of a ramp-incremental exercise. In the deeper portion of the vastus lateralis muscle, this reserve was greater compared with superficial vastus lateralis and rectus femoris. These data suggest that the O2 extraction reserve may be dependent on the vascular and/or oxidative capacities of the muscles.

Association Between Deoxygenated Hemoglobin Breaking Point, Anaerobic Threshold, and Rowing Performance

2019 ◽  
Vol 14 (8) ◽  
pp. 1103-1109
Author(s):  
Tiago Turnes ◽  
Rafael Penteado dos Santos ◽  
Rafael Alves de Aguiar ◽  
Thiago Loch ◽  
Leonardo Trevisol Possamai ◽  
...  
Keyword(s):  
Heart Rate ◽  
Anaerobic Threshold ◽  
Power Output ◽  
Vastus Lateralis ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Breaking Point ◽  
Vastus Lateralis Muscle ◽  
Incremental Test ◽  
Deoxygenated Hemoglobin

Purpose: To compare the intensity and physiological responses of deoxygenated hemoglobin breaking point ([HHb]BP) and anaerobic threshold (AnT) during an incremental test and to verify their association with 2000-m rowing-ergometer performance in well-trained rowers. Methods: A total of 13 male rowers (mean [SD] age = 24 [11] y and  = 63.7 [6.1] mL·kg−1·min−1) performed a step incremental test. Gas exchange, vastus lateralis [HHb], and blood lactate concentration were measured. Power output, , and heart rate of [HHb]BP and AnT were determined and compared with each other. A 2000-m test was performed in another visit. Results: No differences were found between [HHb]BP and AnT in the power output (236 [31] vs 234 [31] W; Δ = 0.7%), 95% confidence interval [CI] 6.7%), (4.2 [0.5] vs 4.3 [0.4] L·min−1; Δ = −0.8%, 95% CI 4.0%), or heart rate (180 [16] vs 182 [12] beats·min−1; Δ = −1.6%, 95% CI 2.1%); however, there was high typical error of estimate (TEE) and wide 95% limits of agreement (LoA) for power output (TEE 10.7%, LoA 54.1–50.6 W), (TEE 5.9%, LoA −0.57 to 0.63 L·min−1), and heart rate (TEE 2.4%, LoA −9.6 to 14.7 beats·min−1). Significant correlations were observed between [HHb]BP (r = .70) and AnT (r = .89) with 2000-m mean power. Conclusions: These results demonstrate a breaking point in [HHb] of the vastus lateralis muscle during the incremental test that is capable of distinguishing rowers with different performance levels. However, the high random error would compromise the use of [HHb]BP for training and testing in rowing.

scholarly journals Neuromuscular fatigue during a long-duration cycling exercise

2002 ◽  
Vol 92 (4) ◽  
pp. 1487-1493 ◽  
Author(s):  
Romuald Lepers ◽  
Nicola A. Maffiuletti ◽  
Ludovic Rochette ◽  
Julien Brugniaux ◽  
Guillaume Y. Millet
Keyword(s):  
Time Course ◽  
Muscle Activation ◽  
Mechanical Response ◽  
Vastus Lateralis ◽  
Quadriceps Muscle ◽  
Voluntary Contraction ◽  
Vastus Lateralis Muscle ◽  
Electromyographic Activity ◽  
Cycling Exercise ◽  
M Wave

The effects of prolonged cycling on neuromuscular parameters were studied in nine endurance-trained subjects during a 5-h exercise sustained at 55% of the maximal aerobic power. Torque during maximal voluntary contraction (MVC) of the quadriceps muscle decreased progressively throughout the exercise ( P < 0.01) and was 18% less at the end of exercise compared with the preexercise value. Peak twitch torque, contraction time, and total area of mechanical response decreased significantly ( P < 0.05) after the first hour of exercise. In contrast, changes in M-wave characteristics were significant only after the fourth hour of the exercise. Significant reductions ( P < 0.05) in electromyographic activity normalized to the M wave occurred after the first hour for the vastus lateralis muscle but only at the end of the exercise for the vastus medialis muscle. Muscle activation level, assessed by the twitch interpolation technique, decreased by 8% ( P < 0.05) at the end of the exercise. The results suggest that the time course is such that the contractile properties are significantly altered after the first hour, whereas excitability and central drive are more impaired toward the latter stages of the 5-h cycling exercise.

INFLUENCE OF KNEE FLEXION DURING SQUAT WITH AND WITHOUT LOAD USING AN INTEGRATED KNEE-FLEXION ANALYSIS SYSTEM

2015 ◽  
Vol 18 (03) ◽  
pp. 1550014
Author(s):  
S. M. N. Arosha Senanayake ◽  
Joko Triloka ◽  
Daphne Lai
Keyword(s):  
Muscle Activity ◽  
Knee Flexion ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Wilcoxon Test ◽  
Strong Positive Correlation ◽  
Paired Samples ◽  
Software Modules ◽  
Integrated Emg ◽  
Analysis System

Purpose: The study analyzed the muscle activity during knee flexion while performing a squat with and without a load based on soft tissue deformation parameters (STDP) at four different angular positions of the vastus lateralis (VL) and vastus medialis (VM) muscles. Methods: An integrated knee-flexion analysis system is a novel tool used to analyze muscle activity during knee flexion and comprises hardware and software modules. A motion capture system and video cameras are interfaced with wireless electromyography (EMG) sensors, and the system software records the motion of the subjects during the squat and extracts relevant features. The STDP from the video of each knee flexion angle and data fusion of EMG, contain the root mean square value, mean absolute value, and integrated EMG of the EMG signals. Twelve healthy soldiers were used as test subjects using uniform criteria in a controlled environment. Results: A strong positive correlation was shown between features extracted using EMG and the STDP for the VL and VM muscles of all subjects. The Wilcoxon test (nonparametric) and paired-samples t-test results were significantly greater in the loaded than unloaded trials during activity of VL and VM muscles at greater knee flexion angles ([Formula: see text]). Conclusion: The outcomes of this study signify the prominence of knee flexion and the associated contiguous balance and co-activation of the VL and VM at 10[Formula: see text], 20[Formula: see text], 30[Formula: see text], and 40[Formula: see text] of knee flexion during squatting with and without an external load. Thus, greater knee flexion during the squat is an important factor for greater muscle activation.

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