Mechanical load increases muscle IGF-I and androgen receptor mRNA concentrations in humans

2001 ◽  
Vol 280 (3) ◽  
pp. E383-E390 ◽  
Author(s):  
Marcas M. Bamman ◽  
James R. Shipp ◽  
Jie Jiang ◽  
Barbara A. Gower ◽  
Gary R. Hunter ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Mechanical Load ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Creatine Kinase Activity ◽  
Total Testosterone ◽  
Vastus Lateralis Muscle ◽  
Mrna Concentration ◽  
Igf I

The mechanism(s) of load-induced muscle hypertrophy is as yet unclear, but increasing evidence suggests a role for locally expressed insulin-like growth factor I (IGF-I). We investigated the effects of concentric (CON) vs. eccentric (ECC) loading on muscle IGF-I mRNA concentration. We hypothesized a greater IGF-I response after ECC compared with CON. Ten healthy subjects (24.4 ± 0.7 yr, 174.5 ± 2.6 cm, 70.9 ± 4.3 kg) completed eight sets of eight CON or ECC squats separated by 6–10 days. IGF-I, IGF binding protein-4 (IGFBP-4), and androgen receptor (AR) mRNA concentrations were determined in vastus lateralis muscle by RT-PCR before and 48 h after ECC and CON. Serum total testosterone (TT) and IGF-I were measured serially across 48 h, and serum creatine kinase activity (CK), isometric maximum voluntary contraction (MVC), and soreness were determined at 48 h. IGF-I mRNA concentration increased 62% and IGFBP-4 mRNA concentration decreased 57% after ECC ( P < 0.05). Changes after CON were similar but not significant ( P = 0.06–0.12). AR mRNA concentration increased ( P < 0.05) after ECC (63%) and CON (102%). Serum TT and IGF-I showed little change. MVC fell 10% and CK rose 183% after ECC ( P < 0.05). Perceived soreness was higher ( P < 0.01) after ECC compared with CON. Results indicate that a single bout of mechanical loading in humans alters activity of the muscle IGF-I system, and the enhanced response to ECC suggests that IGF-I may somehow modulate tissue regeneration after mechanical damage.

Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures

2003 ◽  
Vol 95 (4) ◽  
pp. 1515-1522 ◽  
Author(s):  
L Rochette ◽  
S. K. Hunter ◽  
N Place ◽  
R Lepers
Keyword(s):  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Task Failure ◽  
Rate Of Increase ◽  
Extensor Muscles ◽  
Seated Posture ◽  
Knee Extensor Muscles

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 ± 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 ± 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 ± 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 ± 5.3%), but it ended at a similar value (45.4 ± 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).

Rate of fatigue during repeated submaximal contractions of human quadriceps muscle

1991 ◽  
Vol 69 (10) ◽  
pp. 1410-1415 ◽  
Author(s):  
T. Dolmage ◽  
E. Cafarelli
Keyword(s):  
Vastus Lateralis ◽  
Close Relation ◽  
Quadriceps Muscle ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Vastus Lateralis Muscle ◽  
Relaxation Rates ◽  
Twitch Characteristics ◽  
Rate Of Decline ◽  
Force Time

Our purpose was to determine the effect of eight different combinations of contraction intensity, duration, and rest on the rate of fatigue in vastus lateralis muscle. A single combination consisted of contractions at 30 or 70% maximal voluntary contraction (MVC), held for 3 or 7 s with 3- or 7-s rest intervals. Contractions were repeated until the subject could not hold the force for the requisite duration. At regular intervals during each experiment, a brief MVC, a single twitch, and the response to eight stimulation pulses at 50 Hz were elicited. The rate of fatigue was the rate of decline of MVC calculated from regression analysis. Mean rate of fatigue (n = 8) ranged from 0.3 to 25% MVC/min and was closely related (r = 0.98) to the product of the relative force and the duty cycle. Force from 50 Hz stimulation fell linearly and in parallel with MVC. Twitch force was first potentiated and then fell twice as fast as 50 Hz stimulation and MVC (p < 0.05). Differentiated twitch contraction and relaxation rates were higher at potentiation and lower at the limit of endurance, compared with control values (p < 0.05). The maximal electromyogram decreased 25% and the submaximal EMG increased to maximal by the end of the protocol, indicating that the entire motor unit pool had been recruited. The close relation between rate of fatigue and the force × time product probably reflects the off-setting interaction of contraction amplitude, duration, and rest interval. This occurs despite the changes in twitch characteristics and the apparent recruitment of fast fatiguing motor units.Key words: fatigue, surface EMG, limit of endurance, force × time product, twitch interpolation.

scholarly journals The Neuromuscular Determinants of Unilateral Jump Performance in Soccer Players Are Direction-Specific

2018 ◽  
Vol 13 (5) ◽  
pp. 604-611 ◽  
Author(s):  
Conall F. Murtagh ◽  
Christopher Nulty ◽  
Jos Vanrenterghem ◽  
Andrew O’Boyle ◽  
Ryland Morgans ◽  
...  
Keyword(s):  
Body Mass Index ◽  
Body Mass ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Soccer Players ◽  
Muscle Size ◽  
Fascicle Length ◽  
Jump Performance ◽  
Isometric Maximum Voluntary Contraction

Purpose: To investigate differences in neuromuscular factors between elite and nonelite players and to establish which factors underpin direction-specific unilateral jump performance. Methods: Elite (n = 23; age, 18.1 [1.0] y; body mass index, 23.1 [1.8] kg·m−2) and nonelite (n = 20; age, 22.3 [2.7] y; body mass index, 23.8 [1.8] kg·m−2) soccer players performed 3 unilateral countermovement jumps (CMJs) on a force platform in the vertical, horizontal-forward, and medial directions. Knee extension isometric maximum voluntary contraction torque was assessed using isokinetic dynamometry. Vastus lateralis fascicle length, angle of pennation, quadriceps femoris muscle volume (Mvol), and physiological cross-sectional area (PCSA) were assessed using ultrasonography. Vastus lateralis activation was assessed using electromyography. Results: Elite soccer players presented greater knee extensor isometric maximum voluntary contraction torque (365.7 [66.6] vs 320.1 [62.6] N·m; P = .045), Mvol (2853 [508] vs 2429 [232] cm3; P = .001), and PCSA (227 [42] vs 193 [25] cm2; P = .003) than nonelite. In both cohorts, unilateral vertical and unilateral medial CMJ performance correlated with Mvol and PCSA (r ≥ .310, P ≤ .043). In elite soccer players, unilateral vertical and unilateral medial CMJ performance correlated with upward phase vastus lateralis activation and angle of pennation (r ≥ .478, P ≤ .028). Unilateral horizontal-forward CMJ peak vertical power did not correlate with any measure of muscle size or activation but correlated inversely with angle of pennation (r = −.413, P = .037). Conclusions: While larger and stronger quadriceps differentiated elite from nonelite players, relationships between neuromuscular factors and unilateral jump performance were shown to be direction-specific. These findings support a notion that improving direction-specific muscular power in soccer requires improving a distinct neuromuscular profile.

Human neuromuscular fatigue is associated with altered Na+-K+-ATPase activity following isometric exercise

2002 ◽  
Vol 92 (4) ◽  
pp. 1585-1593 ◽  
Author(s):  
J. R. Fowles ◽  
H. J. Green ◽  
R. Tupling ◽  
S. O'Brien ◽  
B. D. Roy
Keyword(s):  
Atpase Activity ◽  
Maximal Voluntary Contraction ◽  
Vastus Lateralis ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Neuromuscular Fatigue ◽  
Vastus Lateralis Muscle ◽  
M Wave ◽  
Leg Extension ◽  
Muscle Action Potential

The purpose of this study was to investigate the hypothesis that reductions in Na+-K+- ATPase activity are associated with neuromuscular fatigue following isometric exercise. In control (Con) and exercised (Ex) legs, force and electromyogram were measured in 14 volunteers [age, 23.4 ± 0.7 (SE) yr] before and immediately after (PST0), 1 h after (PST1), and 4 h after (PST4) isometric, single-leg extension exercise at ∼60% of maximal voluntary contraction for 30 min using a 0.5 duty cycle (5-s contraction, 5-s rest). Tissue was obtained from vastus lateralis muscle before exercise in Con and after exercise in both the Con (PST0) and Ex legs (PST0, PST1, PST4), for the measurements of Na+-K+-ATPase activity, as determined by the 3- O-methylfluorescein phosphatase (3- O-MFPase) assay. Voluntary (maximal voluntary contraction) and elicited (10, 20, 50, 100 Hz) force was reduced 30–55% ( P < 0.05) at PST0 and did not recover by PST4. Muscle action potential (M-wave) amplitude and area (measured in the vastus medialis) and 3- O-MFPase activity at PST0-Ex were less than that at PST0-Con ( P < 0.05) by 37, 25, and 38%, respectively. M-wave area at PST1-Ex was also less than that at PST1-Con ( P < 0.05). Changes in 3- O-MFPase activity correlated to changes in M-wave area across all time points ( r = 0.38, P < 0.05, n= 45). These results demonstrate that Na+-K+- ATPase activity is reduced by sustained isometric exercise in humans from that in a matched Con leg and that this reduction in Na+-K+-ATPase activity is associated with loss of excitability as indicated by M-wave alterations.

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.

scholarly journals Passive stretching decreases muscle efficiency in balance tasks

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0256656
Author(s):  
Giuseppe Coratella ◽  
Stefano Longo ◽  
Susanna Rampichini ◽  
Christian Doria ◽  
Marta Borrelli ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Balance Control ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Biceps Femoris ◽  
Voluntary Contraction ◽  
Static Stretching ◽  
Balance Tests ◽  
Flexion Extension

The current study aimed to verify whether or not passive static stretching affects balance control capacity. Thirty-eight participants (19 women and 19 men) underwent a passive static stretching session, involving the knee extensor/flexor and dorsi/plantarflexor muscles, and a control session (no stretching, CTRL). Before (PRE), immediately after (POST), after 15 (POST15) and 30 min (POST30) from stretching (or rest in CTRL), balance control was evaluated under static and dynamic conditions, with open/closed eyes, and with/without somatosensory perturbation (foam under the feet). During tests, centre of pressure (CoP) sway area and perimeter and antero-posterior and medio-lateral sway mean speed were computed. Surface electromyography root mean square (sEMG RMS) was calculated from the vastus lateralis, biceps femoris, gastrocnemius medialis, and tibialis anterior muscles during MVC and during the balance tests. Hip flexion/extension and dorsi/plantarflexion range of motion (ROM), maximum voluntary contraction (MVC) and sEMG RMS during MVC were measured at the same time points. After stretching, ROM increased (≈6.5%; P<0.05), while MVC and sEMG RMS decreased (≈9% and ≈7.5%, respectively; P<0.05). Regardless of the testing condition, CoP sway area and the perimeter remained similar, while antero-posterior and medio-lateral sway mean speed decreased by ≈8% and ≈12%, respectively (P<0.05). sEMG RMS during the balance tests increased in all muscles in POST (≈7%, P<0.05). All variables recovered in POST30. No changes occurred in CTRL. Passive static stretching did not affect the overall balance control ability. However, greater muscle activation was required to maintain similar CoP sway, thus suggesting a decrease in muscle efficiency.

Effects of isometric training on the elasticity of human tendon structures in vivo

2001 ◽  
Vol 91 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Keitaro Kubo ◽  
Hiroaki Kanehisa ◽  
Masamitsu Ito ◽  
Tetsuo Fukunaga
Keyword(s):  
Vastus Lateralis ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Vastus Lateralis Muscle ◽  
Electromechanical Delay ◽  
Isometric Training ◽  
Rate Of Torque Development ◽  
Human Tendon ◽  
Torque Development

The present study aimed to investigate the effect of isometric training on the elasticity of human tendon structures. Eight subjects completed 12 wk (4 days/wk) of isometric training that consisted of unilateral knee extension at 70% of maximal voluntary contraction (MVC) for 20 s per set (4 sets/day). Before and after training, the elongation of the tendon structures in the vastus lateralis muscle was directly measured using ultrasonography while the subjects performed ramp isometric knee extension up to MVC. The relationship between the estimated muscle force and tendon elongation ( L) was fitted to a linear regression, the slope of which was defined as stiffness of the tendon structures. The training increased significantly the volume (7.6±4.3%) and MVC torque (33.9±14.4%) of quadriceps femoris muscle. The L values at force production levels beyond 550 N were significantly shorter after training. The stiffness increased significantly from 67.5±21.3 to 106.2±33.4 N/mm. Furthermore, the training significantly increased the rate of torque development (35.8 ± 20.4%) and decreased electromechanical delay (−18.4±3.8%). Thus the present results indicate that isometric training increases the stiffness and Young's modulus of human tendon structures as well as muscle strength and size. This change in the tendon structures would be assumed to be an advantage for increasing the rate of torque development and shortening the electromechanical delay.

Nonlinear relationship between heat production and force during voluntary contractions in humans

1995 ◽  
Vol 79 (6) ◽  
pp. 2043-2049 ◽  
Author(s):  
E. Saugen ◽  
N. K. Vollestad
Keyword(s):  
Vastus Lateralis ◽  
Heat Rate ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Vastus Lateralis Muscle ◽  
Active Muscle ◽  
Lateralis Muscle ◽  
Rate Coding ◽  
Voluntary Contractions ◽  
Typical Subject

The rate of temperature rise (dT/dt) in the vastus lateralis muscle of seven subjects was measured at four to five locations in each muscle during voluntary isometric contractions ranging from 10 to 90% of maximal voluntary contraction (MVC) force. dT/dt increased from 3.1 +/- 1.1 mK/s at 10% MVC to 14.5 +/- 1.3 mK/s at 90% MVC. In the typical subject, the increase in dT/dt with force was markedly higher between 30 and 70% MVC than in the upper and lower force ranges. The estimated ratio between heat rate in active muscle and force was six times higher at 10% MVC than at 90% MVC, indicating a markedly increasing economy of contraction with increasing force. The lower contraction economy at low forces may be explained by an increased rate of energy turnover associated with force generation and relaxation when motor units are contracting at low firing rates. Hence, we argue that recruitment and rate coding may have a profound effect on the economy of contraction at different force levels.

scholarly journals Relationship Between Firing Rate and Recruitment Threshold of Motoneurons in Voluntary Isometric Contractions

2010 ◽  
Vol 104 (2) ◽  
pp. 1034-1046 ◽  
Author(s):  
Carlo J. De Luca ◽  
Emily C. Hostage
Keyword(s):  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Motor Unit Action Potential ◽  
Isometric Contractions ◽  
Healthy Human ◽  
Firing Rates ◽  
Motoneuron Pool ◽  
Emg Signal

We used surface EMG signal decomposition technology to study the control properties of numerous simultaneously active motor units. Six healthy human subjects of comparable age (21 ± 0.63 yr) and physical fitness were recruited to perform isometric contractions of the vastus lateralis (VL), first dorsal interosseous (FDI), and tibialis anterior (TA) muscles at the 20, 50, 80, and 100% maximum voluntary contraction force levels. EMG signals were collected with a five-pin surface array sensor that provided four channels of data. They were decomposed into the constituent action potentials with a new decomposition algorithm. The firings of a total of 1,273 motor unit action potential trains, 20–30 per contraction, were obtained. The recruitment thresholds and mean firing rates of the motor units were calculated, and mathematical equations were derived. The results describe a hierarchical inverse relationship between the recruitment thresholds and the firing rates, including the first and second derivatives, i.e., the velocity and the acceleration of the firing rates. This relationship describes an “operating point” for the motoneuron pool that remains consistent at all force levels and is modulated by the excitation. This relationship differs only slightly between subjects and more distinctly across muscles. These results support the “onion skin” property that suggests a basic control scheme encoded in the physical properties of motoneurons that responds consistently to a “common drive” to the motoneuron pool.

Regulation of lipoprotein lipase in adipose and muscle tissues during fasting

1991 ◽  
Vol 260 (5) ◽  
pp. R953-R959 ◽  
Author(s):  
M. J. Ladu ◽  
H. Kapsas ◽  
W. K. Palmer
Keyword(s):  
Enzyme Activity ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Vastus Lateralis ◽  
Vastus Lateralis Muscle ◽  
Mrna Concentration ◽  
Muscle Tissues ◽  
Lateralis Muscle ◽  
Muscle Changes ◽  
Fast Twitch

The purpose of this work was to determine the relationship between lipoprotein lipase (LPL) activity and LPL mRNA in muscle and adipose tissue in fed and fasted rats. In control animals, the correlation between enzyme activity and LPL mRNA for adipose tissue, heart, soleus, fast red vastus lateralis, and fast white vastus lateralis muscle was r = +0.97. Twenty-four hours of fasting increased LPL activity 38% in heart, reduced it 59% in adipose tissue, and had no effect on activity in the three skeletal muscles analyzed. At the same time, relative LPL mRNA concentrations were reduced 25% in adipose tissue and elevated in heart, soleus, red vastus, and white vastus muscles when compared with control concentrations. Prolonging the fast to 6 days was accompanied by a 64% reduction in adipose tissue LPL activity and an increase in the activities of slow-twitch soleus (83%) and fast-twitch red vastus lateralis muscles (193%), with no enzyme activity change in heart or white vastus lateralis muscle compared with values obtained from control fed animals. LPL mRNA concentration was reduced 66% in adipose tissue, increased more than twofold in heart, soleus, and white vastus muscle, and increased threefold in red vastus muscle. Changes in relative LPL mRNA concentration in adipose tissue induced by fasting could, in part, be accounted for by the increases seen in total RNA concentration. The relationships between enzyme activity and LPL mRNA in muscle and adipose tissue were r = 0.97 and 0.77 for 1-day and 6-day fasted animals, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

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