and EMG Activity Kinetics During Moderate and Severe Constant Work Rate Exercise in Trained Cyclists

2004 ◽  
Vol 29 (6) ◽  
pp. 758-772 ◽  
Author(s):  
Christophe Cleuziou ◽  
Stéphane Perrey ◽  
Fabio Borrani ◽  
Anne Marie Lecoq ◽  
Daniel Courteix ◽  
...  
Keyword(s):  
Slow Component ◽  
Vastus Lateralis ◽  
Bicycle Ergometer ◽  
Lower Limbs ◽  
Emg Activity ◽  
Power Frequency ◽  
Severe Exercise ◽  
Median Power Frequency ◽  
Almost All ◽  
Fast Twitch

The purpose of this study was to compare O2 uptake [Formula: see text] and muscle electromyography activity kinetics during moderate and severe exercise to test the hypothesis of progressive recruitment of fast-twitch fibers in the explanation of the [Formula: see text] slow component. After an incremental test to exhaustion, 7 trained cyclists (mean ± SD, 61.4 ± 4.2 ml•min−1•kg−1) performed several square-wave transitions for 6 min at moderate and severe intensities on a bicycle ergometer. The [Formula: see text] response and the electrical activity (i.e., median power frequency, MDF) of the quadriceps vastus lateralis and vastus medialis of both lower limbs were measured continuously during exercise. After ∼2 to 3 min of exercise onset, MDF values increased similarly during moderate and severe exercise for almost all muscles whereas a [Formula: see text] slow component occurred during severe exercise. There was no relationship between the increase of MDF values and the magnitude of the [Formula: see text] slow component during the severe exercise. These results suggest that the origin of the slow component may not be due to the progressive recruitment of fast-twitch fibers. Key words: median power frequency, O2 uptake, recruitment of fast-twitch fibers, [Formula: see text]slow component

Progressive metabolite changes in individual human muscle fibers with increasing work rates

1987 ◽  
Vol 252 (6) ◽  
pp. C630-C639 ◽  
Author(s):  
J. L. Ivy ◽  
M. M. Chi ◽  
C. S. Hintz ◽  
W. M. Sherman ◽  
R. P. Hellendall ◽  
...  
Keyword(s):  
Blood Lactate ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Lactate Concentration ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Almost All ◽  
Fast Twitch

Muscle biopsies were obtained from vastus lateralis muscles of four volunteers exercising at increasing work rates on a bicycle ergometer. Samples were taken at rest (t1), after a work load 23% below the blood lactate threshold (t2), 23% above this threshold (t3), and at exhaustion (t4). Individual muscle fibers were typed by their lactate dehydrogenase and adenylokinase levels and assayed for lactate, glucose-6-phosphate, and malate, (which preliminary data indicated to be the most responsive to increased activity) as well as ATP and phosphocreatine. The results in three of the four cases indicated that by the time of the t2 sample, almost all fibers, regardless of type, had been recruited. Additionally, there were no major differences in lactate concentration between type 1 and 2 fibers from muscle samples taken at t1, t2, and t3. It is concluded that in a muscle with fast-twitch glycolytic and slow-twitch oxidative fibers, all fibers share in the contraction to a substantial degree, even at moderate work loads, and that both the type 1 and 2 fibers contribute significantly to the initial rise in blood lactate during a graded exercise task. Metabolite responses in type 2 fibers differed in certain respects among the four participants. This is attributed to differences in their training backgrounds and consequent differences in type 2 fiber oxidative enzyme levels.

scholarly journals Vitamin and mineral supplementation effect on muscular activity and cycling efficiency in master athletes

2010 ◽  
Vol 35 (3) ◽  
pp. 251-260 ◽  
Author(s):  
Julien Louis ◽  
Christophe Hausswirth ◽  
François Bieuzen ◽  
Jeanick Brisswalter
Keyword(s):  
Slow Component ◽  
Vastus Lateralis ◽  
Muscular Activity ◽  
Knee Extensors ◽  
Emg Activity ◽  
Master Athletes ◽  
Double Blind ◽  
Mineral Complex ◽  
Cycling Efficiency ◽  
Fatiguing Exercise

The influence of vitamin and mineral complex supplementation on muscular activity and cycling efficiency was examined in elderly endurance-trained master athletes during a heavy cycling trial. Master athletes were randomly assigned in a double-blind process to 1 of 2 treatment groups: antioxidant supplementation (n = 8: As group) or placebo (n = 8: Pl group) for 21 days. After that time, each subject had to perform a 10-min session of cycling on a cycloergometer at a heavy constant intensity. Twenty-four to 48 h after this session, subjects performed an isometric maximal voluntary contraction before and immediately after a fatiguing strength training (leg press exercise) and the same 10-min cycling test after fatigue. Isometric maximal voluntary force (MVF) of knee extensors was assessed before and after fatigue. Electromyographic (EMG) activity of the vastus medialis, the vastus lateralis (VL), and the biceps femoris was recorded with surface EMG. The knee-extensors MVF after the fatiguing exercise was reduced in similar proportions for both groups (As, –10.9%; Pl, –11.3%, p < 0.05). This MVF loss was associated with a significant reduction in EMG frequency parameters for both groups, with a lower decrease for the As group. Muscular activity and cycling efficiency during the cycling bouts were affected by the treatment. Cycling efficiency decreased significantly and the oxygen uptake slow component was higher after the fatiguing exercise for both groups. Furthermore, a decrease in cycling efficiency was associated with an increase in VL activity. However, these changes were significantly lower for the As group. The results of the present study indicate an overall positive effect of vitamin and mineral complex supplementation on cycling efficiency after fatigue, in the endurance-trained elderly.

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 Neural inhibition during maximal eccentric and concentric quadriceps contraction: effects of resistance training

2000 ◽  
Vol 89 (6) ◽  
pp. 2249-2257 ◽  
Author(s):  
P. Aagaard ◽  
E. B. Simonsen ◽  
J. L. Andersen ◽  
S. P. Magnusson ◽  
J. Halkjær-Kristensen ◽  
...  
Keyword(s):  
Resistance Training ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Quadriceps Strength ◽  
Electromyographic Activity ◽  
Neuromuscular Activation ◽  
Concentric Contractions ◽  
Power Frequency ◽  
Heavy Resistance Training ◽  
Median Power Frequency

Despite full voluntary effort, neuromuscular activation of the quadriceps femoris muscle appears inhibited during slow concentric and eccentric contractions. Our aim was to compare neuromuscular activation during maximal voluntary concentric and eccentric quadriceps contractions, hypothesizing that inhibition of neuromuscular activation diminishes with resistance training. In 15 men, pretraining electromyographic activity of the quadriceps muscles [vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF)] was 17–36% lower during slow and fast (30 and 240°/s) eccentric and slow concentric contractions compared with fast concentric contractions. After 14 wk of heavy resistance training, neuromuscular inhibition was reduced for VL and VM and was completely removed for RF. Concurrently, electromyographic activity increased 21–52, 22–29, and 16–32% for VL, VM, and RF, respectively. In addition, median power frequency decreased for VL and RF. Eccentric quadriceps strength increased 15–17%, whereas slow and fast concentric strength increased 15 and 8%, respectively. Pre- and posttraining median power frequency did not differ between eccentric and concentric contractions. In conclusion, quadriceps motoneuron activation was lower during maximal voluntary eccentric and slow concentric contractions compared with during fast concentric contraction in untrained subjects, and, after heavy resistance training, this inhibition in neuromuscular activation was reduced.

scholarly journals Caffeine Supplementation Improves Anaerobic Performance and Neuromuscular Efficiency and Fatigue in Olympic-Level Boxers

Nutrients ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 2120 ◽  
Author(s):  
Alejandro F. San Juan ◽  
Álvaro López-Samanes ◽  
Pablo Jodra ◽  
Pedro L. Valenzuela ◽  
Javier Rueda ◽  
...  
Keyword(s):  
Tibialis Anterior ◽  
Peak Power ◽  
Vastus Lateralis ◽  
Gluteus Maximus ◽  
Wingate Test ◽  
Lower Limbs ◽  
Emg Activity ◽  
Anaerobic Performance ◽  
Mean Power ◽  
Double Blind

Background: this study examined the effects of caffeine supplementation on anaerobic performance, neuromuscular efficiency and upper and lower extremities fatigue in Olympic-level boxers. Methods: Eight male athletes, members of the Spanish National Olympic Team, were enrolled in the study. In a randomized double-blind, placebo-controlled, counterbalanced, crossover design, the athletes completed 2 test sessions after the intake of caffeine (6 mg·kg−1) or placebo. Sessions involved initial measures of lactate, handgrip and countermovement jump (CMJ) performance, followed by a 30-seconds Wingate test, and then final measures of the previous variables. During the sessions, electromiography (EMG) data were recorded on the gluteus maximus, biceps femoris, vastus lateralis, gastrocnemius lateral head and tibialis anterior. Results: caffeine enhanced peak power (6.27%, p < 0.01; Effect Size (ES) = 1.26), mean power (5.21%; p < 0.01; ES = 1.29) and reduced the time needed to reach peak power (−9.91%, p < 0.01; ES = 0.58) in the Wingate test, improved jump height in the CMJ (+2.4 cm, p < 0.01), and improved neuromuscular efficiency at peak power in the vastus lateralis (ES = 1.01) and gluteus maximus (ES = 0.89), and mean power in the vastus lateralis (ES = 0.95) and tibialis anterior (ES = 0.83). Conclusions: in these Olympic-level boxers, caffeine supplementation improved anaerobic performance without affecting EMG activity and fatigue levels in the lower limbs. Further benefits observed were enhanced neuromuscular efficiency in some muscles and improved reaction speed.

Lunges activate the gluteus maximus muscles more than back squats when both exercises are standardized

2021 ◽  
pp. 1-7
Author(s):  
Rodrigo Ramalho Aniceto ◽  
André Luiz Torres Pirauá ◽  
Leonardo da Silva Leandro ◽  
Hélen Cristina Ferreira da Silva ◽  
Diego Mesquita Silva ◽  
...  
Keyword(s):  
Resistance Training ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Gluteus Maximus ◽  
Biceps Femoris ◽  
Lower Limbs ◽  
Emg Activity ◽  
Flexor Muscle ◽  
Back Squat ◽  
Trunk Inclination

BACKGROUND: Squats are considered one of the main exercises for the lower limbs and are used in resistance training under different contexts, including rehabilitation and sports performance. OBJECTIVE: To compare the EMG activity of different muscles in back squat and lunge exercises in trained women. METHODS: Ten healthy women experienced in resistance training performed back squat and lunge exercises on a Smith machine (total work: 70% of 1RM, 1 set, 10 repetitions and 2-s/2-s of execution speed) with an interval of 20-min between exercises. Both exercises were standardized in relation to the trunk inclination and were performed with an erect trunk parallel to the cursor of the guided bar. RESULTS: The EMG activity of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and gluteus maximus (GM) were analyzed. There were no significant differences in the EMG activity of the VM, VL, and BF muscles between the back squat and lunge exercises (P> 0.05); however, GM activation was greater during the lunge exercise (effect size = 1.15; P= 0.001). CONCLUSIONS: Lunges were more effective in recruiting the GM when compared to back squats. However, both exercises can be recommended when the goal is knee extensor and flexor muscle activity.

Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline

2008 ◽  
Vol 105 (2) ◽  
pp. 538-546 ◽  
Author(s):  
Fred J. DiMenna ◽  
Daryl P. Wilkerson ◽  
Mark Burnley ◽  
Andrew M. Jones
Keyword(s):  
Gas Exchange ◽  
Metabolic Rate ◽  
Phase Ii ◽  
Slow Component ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Severe Intensity ◽  
Severe Exercise ◽  
Priming Exercise ◽  
The Difference

It has been suggested that the slower O2 uptake (V̇o2) kinetics observed when exercise is initiated from an elevated baseline metabolic rate are linked to an impairment of muscle O2 delivery. We hypothesized that “priming” exercise would significantly reduce the phase II time constant (τ) during subsequent severe-intensity cycle exercise initiated from an elevated baseline metabolic rate. Seven healthy men completed exercise transitions to 70% of the difference between gas exchange threshold (GET) and peak V̇o2 from a moderate-intensity baseline (90% GET) on three occasions in each of the “unprimed” and “primed” conditions. Pulmonary gas exchange, heart rate, and the electromyogram of m. vastus lateralis were measured during all tests. The phase II V̇o2 kinetics were slower when severe exercise was initiated from a baseline of moderate exercise compared with unloaded pedaling (mean ± SD τ, 42 ± 15 vs. 33 ± 8 s; P < 0.05), but were not accelerated by priming exercise (42 ± 17 s; P > 0.05). The amplitude of the V̇o2 slow component and the change in electromyogram from minutes 2 to 6 were both significantly reduced following priming exercise (V̇o2 slow component: from 0.47 ± 0.09 to 0.27 ± 0.13 l/min; change in integrated electromyogram between 2 and 6 min: from 51 ± 35 to 26±43% of baseline; P < 0.05 for both comparisons). These results indicate that the slower phase II V̇o2 kinetics observed during transitions to severe exercise from an elevated baseline are not altered by priming exercise, but that the reduced V̇o2 slow component may be linked to changes in muscle fiber activation.

Lower Limb EMG Activity during Selected Stepping Exercises

1998 ◽  
Vol 7 (2) ◽  
pp. 102-111 ◽  
Author(s):  
Gilbert M. Willett ◽  
Gregory M. Karst ◽  
Ellen M. Canney ◽  
Derrick Gallant ◽  
Jodene M. Wees
Keyword(s):  
Lower Limb ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Lower Limbs ◽  
Emg Activity ◽  
Muscle Strengthening ◽  
Lower Limb Muscles ◽  
Amplitude Data ◽  
Knee Muscle ◽  
The Right

The purpose of this study was to investigate the electromyographic (EMG) activity of selected lower limb muscles during forward- and backward-facing stair-stepping exercises using a hydraulic step ergometer and during step aerobics using a standard 8 in. high step. Surface electrodes recorded EMG data from the vastus lateralis (VL), vastus medialis obliquus (VMO), and biceps femoris (BF) muscles on the right lower limbs of 13 healthy subjects under each of the four exercise conditions. Normalized mean EMG amplitude data were used to test for activity-dependent differences. Results indicated that (a) the VL and VMO were significantly (p < .05) more active during step ergometry than during step aerobics, (b) the BF was significantly (p < .05) more active during step aerobics than during step ergometry, and (c) when forward- versus backward-facing positions were compared, there were no statistically significant differences in mean EMG activity for either of the activities. These findings provide information relevant to the use and progression of stepping exercises commonly used for knee muscle strengthening and knee injury rehabilitation programs.

scholarly journals Co-contraction training: myoelectric activity and recruitment strategies in an unorthodox resistance training technique.

2021 ◽  
Author(s):  
Nilson Ribeiro dos Santos Silva ◽  
Matheus Pacheco ◽  
Rafael Akira Fujita ◽  
Marina Mello Villalba ◽  
MATHEUS MACHADO GOMES
Keyword(s):  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Voluntary Contraction ◽  
Lower Limbs ◽  
Emg Activity ◽  
Myoelectric Activity ◽  
Muscle Recruitment ◽  
Recruitment Pattern ◽  
Recruitment Patterns

Objective To elucidate the muscle recruitment patterns and interindividual variability during co-contraction training sessions for lower limbs. Methods Ten active male young adults underwent two days of tests, in which they performed, for each leg, a maximal isometric voluntary contraction protocol followed by a co-contraction training set. We acquired myoelectric (EMG) activity from the sartorius, biceps femoris long and short heads, semitendinosus, semimembranosus, rectus femoris, vastus lateralis and vastus medialis and tensor facia latae during both protocols. We used iterative HLM analyses and bootstrap ANOVAs to explain within and between participant variances. Results On average, participants started recruiting 36% of their maximum EMG amplitude, showing decays of 0.41% per repetition and increasing 7.45% from day 1 to day 2. Participants who started with higher recruitment showed greater decays over repetitions and vice-versa. The training stimulated similarly the ratio of participants’ flexors and extensors. However, participants demonstrated different average muscle recruitment patterns with some individuals modifying, largely, their recruitment over repetitions/days. Between and within-variability in recruitment pattern was maintained throughout repetitions and days. We found no consistent similarity in terms of pairs of participants as to find common types of recruitment. Conclusion Co-contraction training seems to be effective to recruit thigh muscles of both legs along an entire set of repetitions and days. Despite the accounted variations in intramuscular recruitment, co-contraction training evokes similar muscular in flexor’s and extensor’s recruitment among participants.

scholarly journals Prevalence of the additional head of quadriceps femoris in the South Indian population: a cadaveric and radiological study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Femina Sam ◽  
Madhavi Kandagaddala ◽  
Ivan James Prithishkumar ◽  
Koyeli Mary Mahata ◽  
Mahasampath Gowri ◽  
...  
Keyword(s):  
Indian Population ◽  
Vastus Lateralis ◽  
Femoral Nerve ◽  
Quadriceps Femoris ◽  
Lower Limbs ◽  
South Indian Population ◽  
The South ◽  
South Indian ◽  
Circumflex Femoral Artery ◽  
Vastus Intermedius

AbstractQuadriceps femoris is an extensor muscle in the anterior compartment of thigh and is traditionally taught to be composed of four heads. Recently, there is an increased interest in the occurrence of an additional muscle head of quadriceps femoris. But scientific knowledge regarding its incidence is lacking in the South Indian population. This study was done to confirm the presence of the additional head by routine anatomic dissection and radiological imaging techniques. Forty-one formalin fixed human cadaveric lower limbs were dissected and the morphology of the additional head was noted. Retrospective analysis of 88 MRI images of patients was done. The additional muscle head was present in 43.9% of the cadaveric lower limbs and was consistently located between the vastus lateralis and vastus intermedius. It originated from variable portions of the greater trochanter, intertrochanteric line, lateral lip of linea aspera and lateral surface of the shaft of femur and inserted either as a muscle belly or as an aponeurosis into the vastus intermedius (55.6%), vastus lateralis (22.2%) or directly into the base of the patella. It received its vascular supply from branches of the lateral circumflex femoral artery and was innervated by branches from the posterior division of the femoral nerve. In addition, the additional muscle head was identified by MRI and its incidence was reported to be 30.68% for the first time in living subjects. The result of this study provides additional information in understanding the morphology of the quadriceps femoris muscle.

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