scholarly journals Intramuscular fiber conduction velocity, isometric force and explosive performance

2016 ◽  
Vol 51 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Spyridon Methenitis ◽  
Gerasimos Terzis ◽  
Nikolaos Zaras ◽  
Angeliki-Nikoletta Stasinaki ◽  
Nikolaos Karandreas
Keyword(s):  
Conduction Velocity ◽  
Muscle Fiber ◽  
Isometric Force ◽  
Vastus Lateralis ◽  
Rate Of Force Development ◽  
Muscle Fiber Conduction Velocity ◽  
Force Development ◽  
Leg Press ◽  
Explosive Performance ◽  
Maximum Isometric Force

Abstract Conduction of electrical signals along the surface of muscle fibers is acknowledged as an essential neuromuscular component which is linked with muscle force production. However, it remains unclear whether muscle fiber conduction velocity (MFCV) is also linked with explosive performance. The aim of the present study was to investigate the relationship between vastus lateralis MFCV and countermovement jumping performance, the rate of force development and maximum isometric force. Fifteen moderately-trained young females performed countermovement jumps as well as an isometric leg press test in order to determine the rate of force development and maximum isometric force. Vastus lateralis MFCV was measured with intramuscular microelectrodes at rest on a different occasion. Maximum MFCV was significantly correlated with maximum isometric force (r = 0.66, p < 0.01), nevertheless even closer with the leg press rate of force development at 100 ms, 150 ms, 200 ms, and 250 ms (r = 0.85, r = 0.89, r = 0.91, r = 0.92, respectively, p < 0.01). Similarly, mean MFCV and type II MFCV were better correlated with the rate of force development than with maximum isometric leg press force. Lower, but significant correlations were found between mean MFCV and countermovement jump power (r = 0.65, p < 0.01). These data suggest that muscle fiber conduction velocity is better linked with the rate of force development than with isometric force, perhaps because conduction velocity is higher in the larger and fastest muscle fibers which are recognized to contribute to explosive actions.

Muscle fiber composition, jumping performance, and rate of force development adaptations induced by different power training volumes in females

2020 ◽  
Vol 45 (9) ◽  
pp. 996-1006 ◽  
Author(s):  
Spyridon Methenitis ◽  
Thomas Mpampoulis ◽  
Polyxeni Spiliopoulou ◽  
George Papadimas ◽  
Constantinos Papadopoulos ◽  
...  
Keyword(s):  
Muscle Fiber ◽  
Isometric Force ◽  
Fiber Type ◽  
High Volume ◽  
Rate Of Force Development ◽  
Training Volume ◽  
Power Training ◽  
Power Performance ◽  
Force Development ◽  
Low Volume

This study aimed to investigate the effect of 3 different eccentric-only power training volumes on muscle fiber type composition and power performance. Twenty-nine females were assigned into 3 groups and performed 10 weeks of either 3 (low volume), 6 (moderate volume), or 9 (high volume) sets/session of 4 fast-velocity eccentric-only half-squats against 70% of concentric 1-repetition maximum (1RM), followed by 3 maximum countermovement jumps (CMJs) after each set. Half-squat 1RM, CMJ height/power, maximum isometric force, rate of force development (RFD) and muscle fiber cross-sectional area (CSA) were increased in all groups (p = 0.001). Low-volume training induced higher increases in CMJ height/power and early RFD, compared with the moderate- and high-volume training programs (p < 0.001). Significant reductions in type IIx muscle fiber percentages and %CSAs were found after moderate- and high-volume training, with concomitant increases in type IIa fibers (p = 0.001). Significant correlations were found between the changes in type IIa and type IIx percentages, fiber CSA, %CSA, and the changes in performance (r: –0.787 to 0.792; p < 0.05). These results suggest that relatively large eccentric power training volumes may result in detrimental neuromuscular adaptations, minimal changes in early RFD, and a reduction of type IIx muscle fiber percentage. Novelty Low but not high volume of power training maintains type IIx muscle fibers. Early rate of force development increases after a low- or moderate-power training volume, but not after a high-power training volume. Training-induced changes in type IIx muscle fiber percentage is related with changes in early rate of force development.

scholarly journals Selective muscle hypertrophy, changes in EMG and force, and serum hormones during strength training in older women

2001 ◽  
Vol 91 (2) ◽  
pp. 569-580 ◽  
Author(s):  
Keijo Häkkinen ◽  
Arto Pakarinen ◽  
William J. Kraemer ◽  
Arja Häkkinen ◽  
Heli Valkeinen ◽  
...  
Keyword(s):  
Strength Training ◽  
Older Women ◽  
Muscle Hypertrophy ◽  
Isometric Force ◽  
Vastus Lateralis ◽  
Rate Of Force Development ◽  
Limiting Factor ◽  
Type I ◽  
Time Duration ◽  
Force Development

Effects of strength training (ST) for 21 wk were examined in 10 older women (64 ± 3 yr). Electromyogram, maximal isometric force, one-repetition maximum strength, and rate of force development of the leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF) and of vastus lateralis (VL), medialis (VM), intermedius (VI) and rectus femoris (RF) throughout the lengths of 3/12–12/15 (Lf) of the femur, muscle fiber proportion and areas of types I, IIa, and IIb of the VL were evaluated. Serum hormone concentrations of testosterone, growth hormone (GH), cortisol, and IGF-I were analyzed for the resting, preexercise, and postexercise conditions. After the 21-wk ST, maximal force increased by 37% ( P < 0.001) and 1-RM by 29% ( P < 0.001), accompanied by an increase ( P < 0.01) in rate of force development. The integrated electromyograms of the vastus muscles increased ( P < 0.05). The CSA of the total QF increased ( P < 0.05) throughout the length of the femur by 5–9%. The increases were significant ( P< 0.05) at 7/15–12/15 Lf for VL and at 3/15–8/15 Lf for VM, at 5/15–9/15 for VI and at 9/15 ( P < 0.05) for RF. The fiber areas of type I ( P < 0.05), IIa ( P < 0.001), and IIb ( P < 0.001) increased by 22–36%. No changes occurred during ST in serum basal concentrations of the hormones examined, but the level of testosterone correlated with the changes in the CSA of the QF ( r = 0.64, P < 0.05). An acute increase of GH ( P < 0.05), remaining elevated up to 30 min ( P < 0.05) postloading, was observed only at posttraining. Both neural adaptations and the capacity of skeletal muscle to undergo training-induced hypertrophy even in older women explain the strength gains. The increases in the CSA of the QF occurred throughout its length but differed selectively between the individual muscles. The serum concentrations of hormones remained unaltered, but a low level of testosterone may be a limiting factor in training-induced muscle hypertrophy. The magnitude and time duration of the acute GH response may be important physiological indicators of anabolic adaptations during strength training even in older women.

scholarly journals Evaluation of Strength and Muscle Activation Indicators in Sticking Point Region of National-Level Paralympic Powerlifting Athletes

2021 ◽  
Vol 6 (2) ◽  
pp. 43
Author(s):  
Felipe J. Aidar ◽  
Filipe Manuel Clemente ◽  
Dihogo Gama de Matos ◽  
Anderson Carlos Marçal ◽  
Raphael Fabrício de Souza ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
National Level ◽  
Rate Of Force Development ◽  
Static Test ◽  
Force Development ◽  
Intermediate Phases ◽  
Maximum Isometric Force ◽  
Dynamic Time ◽  
Sticking Point

Background: The sticking region is considered an intervening factor in the performance of the bench press with high loads. Objective: To evaluate the strength indicators in the sticking point region in Powerlifting Paralympic athletes. Methods: Twelve Brazilian Powerlifting Paralympic athletes performed maximum isometric force (MIF), rate of force development (RFD), time at MIF, velocity, dynamic time in sticking, and surface electromyography in several distances from the bar to the chest. Results: For velocity, there was a difference between the pre-sticking and sticking region (1.98 ± 0.32 and 1.30 ± 0.43, p = 0.039) and dynamic time between the pre-sticking and the sticking region (0.40 ± 0.16 and 0.97 ± 0.37, p = 00.021). In static test for the MIF, differences were found between 5.0 cm and 15.0 cm (CI 95% 784; 1088; p = 0.010) and between 10.0 cm and 5.0 cm (CI 95% 527; 768; p < 0.001). Regarding the RFD, differences were found (CI 95% 938; 1240; p = 0.004) between 5.0 cm and 25.0 cm and between 10.0 cm and 25.0 cm (CI 95% 513; 732; p < 0.001). In relation to time, there were differences between 5.0 cm and 15.0 cm (CI 95% 0.330; 0.515; p < 0.001), 5.0 cm, and 25.0 cm (CI 95% 0.928; 1.345; p = 0.001), 10.0 cm and 15.0 cm (p < 0.05) and 15.0 cm and 25.0 cm (p < 0.05). No significant differences were observed between the muscles in electromyography, although the triceps showed the highest muscle activation values. Conclusions: The maximum isometric force, rate of force development, time, velocity, and dynamic time had lower values, especially in the initial and intermediate phases in the sticking region.

Effect of power, pedal rate, and force on average muscle fiber conduction velocity during cycling

2004 ◽  
Vol 97 (6) ◽  
pp. 2035-2041 ◽  
Author(s):  
Dario Farina ◽  
Andrea Macaluso ◽  
Richard A. Ferguson ◽  
Giuseppe De Vito
Keyword(s):  
Conduction Velocity ◽  
Muscle Fiber ◽  
External Force ◽  
Power Output ◽  
Vastus Lateralis ◽  
Force Production ◽  
Motor Units ◽  
Angular Speed ◽  
Muscle Fiber Conduction Velocity ◽  
Pedal Rate

Muscle fiber conduction velocity (MFCV) provides indications on motor unit recruitment strategies due to the relation between conduction velocity and fiber diameter. The aim of this study was to investigate MFCV of thigh muscles during cycling at varying power outputs, pedal rates, and external forces. Twelve healthy male participants aged between 19 and 30 yr cycled on an electronically braked ergometer at 45, 60, 90, and 120 rpm. For each pedal rate, subjects performed two exercise intensities, one at an external power output corresponding to the previously determined lactate threshold (100% LT) and the other at half of this power output (50% LT). Surface electromyogram signals were detected during cycling from vastus lateralis and medialis muscles with linear adhesive arrays of eight electrodes. In both muscles, MFCV was higher at 100% LT compared with 50% LT for all average pedal rates except 120 rpm (mean ± SE, 4.98 ± 0.19 vs. 4.49 ± 0.18 m/s; P < 0.001). In all conditions, MFVC increased with increasing instantaneous knee angular speed (from 4.14 ± 0.16 to 5.08 ± 0.13 m/s in the range of instantaneous angular speeds investigated; P < 0.001). When MFCV was compared at the same external force production (i.e., 90 rpm/100% LT vs. 45 rpm/50% LT, and 120 rpm/100% LT vs. 60 rpm/50% LT), MFCV was higher at the faster pedal rate (5.02 ± 0.17 vs. 4.64 ± 0.12 m/s, and 4.92 ± 0.19 vs. 4.49 ± 0.11 m/s, respectively; P < 0.05) due to the increase in inertial power required to accelerate the limbs. It was concluded that, during repetitive dynamic movements, MFCV increases with the external force developed, instantaneous knee angular speed, and average pedal rate, indicating progressive recruitment of large, high conduction velocity motor units with increasing muscle force.

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction

2020 ◽  
Vol 30 (10) ◽  
pp. 1976-1984
Author(s):  
Stefano Nuccio ◽  
Alessandro Del Vecchio ◽  
Andrea Casolo ◽  
Luciana Labanca ◽  
Jacopo Emanuele Rocchi ◽  
...  
Keyword(s):  
Acl Reconstruction ◽  
Conduction Velocity ◽  
Muscle Fiber ◽  
Vastus Lateralis ◽  
Soccer Players ◽  
Muscle Fiber Conduction Velocity

Effect of fatigue on rate of isometric force development in mouse fast- and slow-twitch muscles

1992 ◽  
Vol 263 (5) ◽  
pp. C1065-C1072 ◽  
Author(s):  
C. J. Barclay
Keyword(s):  
Energy Expenditure ◽  
Extensor Digitorum Longus ◽  
Initial Rate ◽  
Isometric Force ◽  
Rate Of Force Development ◽  
Force Development ◽  
Maximum Isometric Force ◽  
Slow Twitch ◽  
Rapid Activation

Changes in the rate of isometric force development with fatigue were measured in vitro (25 degrees C) using mouse soleus and extensor digitorum longus (EDL) muscles. Muscles were fatigued using 30 tetanic contractions. Rate of force development was determined from the rate constant of an exponential curve fitted to the rising force phase of a tetanus. For both muscles, when the intertetanus interval was 3 s, maximum isometric force and relaxation rate were significantly reduced in the final tetanus relative to the values in the first tetanus. Rate of force development in soleus muscles transiently increased and then decreased a small amount. The final rate was 92.7 +/- 3.3% (n = 4) of the initial rate. In contrast, the rate of force development in EDL muscles increased to 133.7 +/- 3.3% (n = 4) of the initial rate. This increased rate was evident from the second tetanus of the series, was fully established after 5 tetani, and the magnitude of the increase in rate was inversely proportional to intertetanus interval and was independent of presumed energy expenditure. The enhanced rate decayed with a time constant of 14.3 +/- 2.0 s and was independent of presumed energy expenditure. Most of these observations can be explained by the effects of P(i) on cross bridge kinetics. Other possible mechanisms, involving more rapid activation, are also suggested.

Changes in muscle fiber conduction velocity indicate recruitment of distinct motor unit populations

2003 ◽  
Vol 95 (3) ◽  
pp. 1045-1054 ◽  
Author(s):  
C. J. Houtman ◽  
D. F. Stegeman ◽  
J. P. Van Dijk ◽  
M. J. Zwarts
Keyword(s):  
Conduction Velocity ◽  
Muscle Fiber ◽  
Tibialis Anterior Muscle ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Type I ◽  
Muscle Fiber Conduction Velocity ◽  
Depth Study

To obtain more insight into the changes in mean muscle fiber conduction velocity (MFCV) during sustained isometric exercise at relatively low contraction levels, we performed an in-depth study of the human tibialis anterior muscle by using multichannel surface electromyogram. The results show an increase in MFCV after an initial decrease of MFCV at 30 or 40% maximum voluntary contraction in all of the five subjects studied. With a peak velocity analysis, we calculated the distribution of conduction velocities of action potentials in the bipolar electromyogram signal. It shows two populations of peak velocities occurring simultaneously halfway through the exercise. The MFCV pattern implies the recruitment of two different populations of motor units. Because of the lowering of MFCV of the first activated population of motor units, the newly recruited second population of motor units becomes visible. It is most likely that the MFCV pattern can be ascribed to the fatiguing of already recruited predominantly type I motor units, followed by the recruitment of fresh, predominantly type II, motor units.

Acute Physiological Response to Light- and Heavy-load Power-oriented Exercise in Older Adults

2021 ◽  
Author(s):  
Carlos Rodriguez-Lopez ◽  
Julian Alcazar ◽  
Jose Losa-Reyna ◽  
JuanManuel Carmona-Torres ◽  
Aurora Maria Cruz-Santaella ◽  
...  
Keyword(s):  
Older Adults ◽  
Creatine Kinase ◽  
Resistance Training ◽  
Isometric Force ◽  
Rate Of Force Development ◽  
Heavy Load ◽  
Force Development ◽  
Sit To Stand ◽  
Light Load ◽  
Maximal Isometric Force

AbstractThis study investigated the acute responses to volume-load-matched heavy-load (80% 1RM) versus light-load (40% 1RM) power-oriented resistance training sessions in well-functioning older adults. Using a randomized cross-over design, 15 volunteers completed each condition on a leg press. Neuromuscular (maximal isometric force and rate of force development) and functional performance (power during sit-to-stand test), lactate, and muscle damage biochemistry (creatine kinase, lactate dehydrogenase and C-reactive protein serum concentration) were assessed pre- and post-exercise. Performance declines were found after heavy-load (Cohen’s d effect size (d); maximal isometric force=0.95 d; rate of force development=1.17 d; sit-to-stand power =0.38 d, all p<0.05) and light-load (maximal isometric force=0.45 d; rate of force development=0.9 d; sit-to-stand power=1.17 d, all p<0.05), while lactate concentration increased only after light-load (1.7 d, p=0.001). However, no differences were found between conditions (all p>0.05). Both conditions increased creatine kinase the day after exercise (marginal effect=0.75 d, p<0.001), but no other blood markers increased (all, p>0.05). Irrespective of the load used, power training induced non-clinically significant decreases in sit-to-stand performance, moderate declines in maximal isometric force, but pronounced decreases in the rate of force development. Furthermore, the metabolic stress and muscle damage were minor; both sessions were generally well tolerated by well-functioning older adults without previous experience in resistance training.

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