The length dependency of maximum force development in rat medial gastrocnemius muscle in situ

2008 ◽  
Vol 33 (3) ◽  
pp. 518-526 ◽  
Author(s):  
Cornelis J. de Ruiter ◽  
Tinelies E. Busé-Pot ◽  
Arnold de Haan
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
Force Production ◽  
Time History ◽  
Medial Gastrocnemius ◽  
Force Output ◽  
Force Development ◽  
Activation Times ◽  
Maximal Isometric Force

During many movements (e.g., running, jumping, and kicking) there is little time for skeletal muscles to build up force, thus rapid force development is important. The length dependency of isometric force development was investigated in maximally activated rat medial gastrocnemius muscles in situ with intact blood flow at 35 °C. Depending on time available for muscle activation, the length dependency of force development was expected to differ from that of the maximal isometric force (Fmax) reached much later during the contraction. During isometric force development in intact muscle–tendon preparations, the contractile elements actually shortened. Therefore, similar to previous findings on shortening contractions, it was hypothesized that maximal rate of force development (MRFD) would be obtained at a length below the optimum (Lo) for maximal isometric force production. To measure the effect of the entire time history of activation, force time integrals (FTIs) for different activation times (10–50 ms) were also calculated. The highest MRFD was obtained 1.94 ± 0.42 mm below (p < 0.05) Lo. When expressed relative to Fmax obtained at each individual length, the optimum was found at Lo – 4.4 mm. For FTI 10 ms and FTI 20 ms, optimum length was obtained at ~2 and 1 mm above (p < 0.05) Lo, respectively, whereas the optima for FTI 30, 40, and 50 ms were ~1 mm below (p < 0.05) Lo. In addition, at short lengths (< Lo – 4 mm) and for all activation times FTIs were relatively more decreased than Fmax. In conclusion, length dependency of force output during rapid force development differed from that of maximal isometric force; specifically, MRFD was obtained 2 mm below Lo.

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.

Modeling constraints to redundancy in bimanual force coordination

2011 ◽  
Vol 105 (5) ◽  
pp. 2169-2180 ◽  
Author(s):  
Xiaogang Hu ◽  
Karl M. Newell
Keyword(s):  
Muscle Force ◽  
Coupling Effect ◽  
Isometric Force ◽  
Force Production ◽  
Force Output ◽  
Task Constraints ◽  
Task Goal ◽  
Force Coordination ◽  
Finger Forces ◽  
Coordination Patterns

This study investigated the interactive influence of organismic, environmental, and task constraints on the organization of redundant force coordination patterns and the hypothesis that each of the three categories of constraints is weighted based on their relative influence on coordination patterns and the realization of the task goal. In the bimanual isometric force experiment, the task constraint was manipulated via different coefficients imposed on the finger forces such that the weighted sum of the finger forces matched the target force. We examined three models of task constraints based on the criteria of task variance (minimum variance model) and efficiency of muscle force output (coefficient-independent and coefficient-dependent efficiency models). The environmental constraint was quantified by the perceived performance error, and the organismic constraint was quantified by the bilateral coupling effect (i.e., symmetric force production) between hands. The satisficing approach was used in the models to quantify the constraint weightings that reflect the interactive influence of different categories of constraints on force coordination. The findings showed that the coefficient-dependent efficiency model best predicted the redundant force coordination patterns across trials. However, the within-trial variability structure revealed that there was not a consistent coordination strategy in the online control of the individual trial. The experimental findings and model tests show that the force coordination patterns are adapted based on the principle of minimizing muscle force output that is coefficient dependent rather than on the principle of minimizing signal-dependent variance. Overall, the results support the proposition that redundant force coordination patterns are organized by the interactive influence of different categories of constraints.

scholarly journals Force production and muscle activation during partial vs. full range of motion in Paralympic Powerlifting

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0257810
Author(s):  
Tanise Pires Mendonça ◽  
Felipe José Aidar ◽  
Dihogo Gama Matos ◽  
Raphael Fabrício Souza ◽  
Anderson Carlos Marçal ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Muscle Activation ◽  
Isometric Force ◽  
Full Range ◽  
Pectoralis Major Muscle ◽  
National Level ◽  
Force Production ◽  
Muscle Thickness ◽  
Pectoralis Major ◽  
Post Exercise

Paralympic Powerlifting is a sport in which the strength of the upper limbs is assessed through bench press performance in an adapted specific bench. It is therefore essential to optimize training methods to maximize this performance. The aim of the present study was to compare force production and muscle activation involved in partial vs. full range of motion (ROM) training in Paralympic Powerlifting. Twelve male athletes of elite national level in Paralympic Powerlifting participated in the study (28.60 ± 7.60 years of age, 71.80 ± 17.90 kg of body mass). The athletes performed five sets of 5RM (repetition maximum), either with 90% of 1RM in full ROM or with a load of 130% 1RM in partial ROM. All subjects underwent both exercise conditions in consecutive weeks. Order assignment in the first week was random and counterbalanced. Fatigue index (FI), Maximum Isometric Force (MIF), Time to MIF (Time) and rate of force development (RFD) were determined by a force sensor. Muscle thickness was obtained using ultrasound images. All measures were taken pre- and post-training. Additionally, electromyographic signal (EMG) was evaluated in the last set of each exercise condition. Post-exercise fatigue was higher with full ROM as well as loss of MIF. Full ROM also induced greater. EMG showed greater activation of the Clavicular portion and Sternal portion of pectoralis major muscle and lower in the anterior portion of deltoid muscle when full ROM was performed. Muscle thickness of the pectoralis major muscle increased post-exercise. We concluded that training with partial ROM enables higher workloads with lower loss of muscle function.

scholarly journals Effects of submaximal cycling at different exercise intensities on maximal isometric force output of the non-exercised elbow flexor muscles

2018 ◽  
Vol 105 (2) ◽  
pp. 177-187
Author(s):  
R Matsuura ◽  
K Hirakoba ◽  
K Takahashi
Keyword(s):  
Isometric Force ◽  
Lactate Concentration ◽  
Elbow Flexor ◽  
Emg Activity ◽  
Force Output ◽  
Cardiorespiratory Responses ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
The Right ◽  
Maximal Isometric Force

The purpose of this study was to examine the effects of submaximal cycling at different exercise intensities on maximal isometric force output of the non-exercised elbow flexor muscles after the cycling. A total of 8 healthy young men performed multiple maximal voluntary contractions by the right elbow flexion before, immediately after, 5 min after, and 10 min after a 6-min submaximal cycling at ventilatory threshold (LI), 70% (MI), and 80% (HI) with both arms relaxed in the air. Force and surface electromyogram (EMG) of the right biceps brachii muscle during the multiple MVCs, blood lactate concentration ([La]), cardiorespiratory responses, and sensations of fatigue for legs (SEF-L) were measured before, immediately after, 5 min after, and 10 min after the submaximal cycling with the three different exercise intensities. Immediately after the submaximal cycling, [La], cardiorespiratory responses, and SEF-L were enhanced in proportion to an increase in exercise intensity of the cycling. Changes in force and EMG activity during the multiple MVCs were not significantly different across the three conditions. The findings imply that group III/IV muscle afferent feedback after the submaximal cycling does not determine the magnitude of MVC force loss of the non-exercised upper limb muscles.

scholarly journals Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance

2016 ◽  
Vol 53 (1) ◽  
pp. 201-210 ◽  
Author(s):  
Klaus Wirth ◽  
Michael Keiner ◽  
Hagen Hartmann ◽  
Andre Sander ◽  
Christoph Mickel
Keyword(s):  
Strength Training ◽  
Repeated Measures ◽  
Isometric Force ◽  
Countermovement Jump ◽  
Squat Jump ◽  
Repetition Maximum ◽  
Force Development ◽  
Leg Press ◽  
Free Weight ◽  
Maximal Isometric Force

AbstractThe aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance.

Effect of gradual reduction in O2 delivery on intracellular homeostasis in contracting skeletal muscle

1996 ◽  
Vol 80 (4) ◽  
pp. 1313-1321 ◽  
Author(s):  
M. C. Hogan ◽  
S. S. Kurdak ◽  
P. G. Arthur
Keyword(s):  
Skeletal Muscle ◽  
Muscle Blood Flow ◽  
Force Production ◽  
Tight Coupling ◽  
Gradual Reduction ◽  
Force Development ◽  
Atp Supply ◽  
O2 Delivery ◽  
Arterial Po2

This study was designed to investigate 1) whether a protocol employing a gradual reduction in O2 availability to submaximally contracting muscle results in relatively minor disturbances in intracellular homeostasis and 2) the interaction between tissue oxygenation and the proposed regulators of muscle respiration, metabolism, and force production. O2 delivery to isolated submaximally contracting [isometric contractions at 3 Hz; approximately 50% of peak O2 uptake (VO2)] in situ canine gastrocnemius (n = 6) was manipulated by decreasing arterial PO2 (hypoxemia; H) or muscle blood flow (ischemia; I) during three separate periods in each muscle [control (C), H, or I; each separated by 45 min of rest]. O2 delivery was reduced gradually in small steps every 3 min by H or I during two of the contraction periods (6 steps for a total of 21 min; O2 delivery reduced by 67% by the end of 21 min), whereas C was at normal O2 delivery for a 15-min period. Muscle VO2 was maintained at control levels for the first two O2 delivery reduction steps for the H and I conditions and then fell proportionally with O2 delivery to approximately 35% of the initial value by the end of the 21-min contraction period. Muscle force development generally fell in parallel with VO2. There was no significant changes from the values obtained during C contractions in intracellular concentrations of ATP, phosphocreatine, NH3, calculated free ADP, lactate, and redox state ratios as the O2 delivery was reduced, even with the severe decline in VO2 and developed force. These results demonstrated that when O2 availability was reduced gradually to contracting skeletal muscle, 1) developed force (ATP utilization) was reduced through a tight coupling with aerobic ATP supply, such that there was little additional disruption of intracellular homeostasis, and 2) there was an apparent dissociation of some of the proposed regulators of cell respiration and force development from the control of these processes.

MODELING THE CONTROL OF ISOMETRIC FORCE PRODUCTION WITH PIECE-WISE LINEAR, STOCHASTIC MAPS OF MULTIPLE TIME-SCALES

2003 ◽  
Vol 03 (01) ◽  
pp. L23-L29 ◽  
Author(s):  
GOTTFRIED MAYER-KRESS ◽  
KATHERINE M. DEUTSCH ◽  
KARL M. NEWELL
Keyword(s):  
Time Scales ◽  
Isometric Force ◽  
Force Production ◽  
Human Movement ◽  
Multiple Time Scales ◽  
Force Variability ◽  
Multiple Time ◽  
Force Level ◽  
Force Output ◽  
Isometric Force Production

In human movement, the large number of system degrees of freedom at different levels of analysis of the system, joints, muscles, motor units, cells etc, naturally affords complexity and adaptability in action. It also leads to variability in movement and its outcome, even in intentional efforts to reproduce the same movement or action goal. An example is continuous isometric force output to a constant force level where the amount and structure of force variability changes with information available, force level and individual differences. In this paper we model the control of isometric force production with piece-wise linear stochastic maps of multiple time scales. At the core of our model is a piecewise linear function, depending on three parameters that can be estimated from the observed data that is perturbed by additive Gaussian noise at a given level. The result of the stochastic forcing is that outside of a threshold interval the system behaves like a discrete Ornstein-Uhlenbeck process and inside it performs a Brownian motion. The model is shown to simulate the basic findings of the structure of human force variability that decreasing variability is correlated with increased dynamical complexity as measured with the "Approximate Entropy (ApEn)" statistic.

Prefrontal cortex oxygenation is preserved and does not contribute to impaired neuromuscular activation during passive hyperthermia

2009 ◽  
Vol 34 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Shawnda A. Morrison ◽  
Gordon G. Sleivert ◽  
J. Patrick Neary ◽  
Stephen S. Cheung
Keyword(s):  
Prefrontal Cortex ◽  
Cerebral Oxygenation ◽  
Isometric Force ◽  
Thermal Strain ◽  
Force Production ◽  
Knee Extension ◽  
Voluntary Activation ◽  
Passive Heating ◽  
Force Output ◽  
Passive Hyperthermia

We investigated the role of passive hyperthermia upon motor unit activation and prefrontal cortex oxygenation. Six healthy males were passively heated, using a liquid conditioning garment in a hot environment (35 °C, 50% relative humidity). Maximal force output and voluntary activation were examined during a 10 s maximal isometric knee extension. Of the initial 6 subjects, 1 experienced syncope at a rectal temperature (Tre) of 38.0 °C and was removed from the study. The remaining 5 subjects completed heating and testing to a Tre of 38.5 °C (n = 1), 39.0 °C (n = 3), or 39.5 °C (n = 1), and then were cooled back to baseline. Force production decreased from 553 ± 133 to 430 ± 176 N (p < 0.01) with passive heating, as did voluntary activation (from 90 ± 5% to 84 ± 7%). Percent heart rate reserve increased from 8 ± 5% to 59 ± 3% before returning to 4 ± 8% (p < 0.001). Although mean arterial pressure remained unchanged, there were significant decreases in diastolic blood pressure with heating (80 ± 3 to 63 ± 8 mm Hg). Passive heating did not alter prefrontal cortex oxygenation, but cooling back to baseline core temperature attenuated cerebral oxygenated and total hemoglobin levels (p < 0.05). Passive heating to the point of voluntary exhaustion elevated cardiovascular and thermal strain and subjective perceptions of thermal discomfort. However, while this resulted in a marked decrement in maximal isometric force production and central voluntary activation, no concomitant changes in cerebral oxygenation were observed, suggesting that overall cerebrovascular regulation was maintained.

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