scholarly journals Older Compared With Younger Adults Performed 467 Fewer Sit-to-Stand Trials, Accompanied by Small Changes in Muscle Activation and Voluntary Force

2021 ◽  
Vol 13 ◽  
Author(s):  
Paulo Cezar Rocha dos Santos ◽  
Claudine J. C. Lamoth ◽  
Lilian Teresa Bucken Gobbi ◽  
Inge Zijdewind ◽  
Fabio Augusto Barbieri ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Perceived Exertion ◽  
Knee Extension ◽  
Age Effects ◽  
Younger Adults ◽  
Perturbation Model ◽  
Sit To Stand ◽  
Rate Of Perceived Exertion ◽  
Isometric Knee Extension ◽  
Extension Force

Background: Repetitive sit-to-stand (rSTS) is a fatigue perturbation model to examine the age-effects on adaptability in posture and gait, yet the age-effects on muscle activation during rSTS per se are unclear. We examined the effects of age and exhaustive rSTS on muscle activation magnitude, onset, and duration during ascent and descent phases of the STS task.Methods: Healthy older (n = 12) and younger (n = 11) adults performed rSTS, at a controlled frequency dictated by a metronome (2 s for cycle), to failure or for 30 min. We assessed muscle activation magnitude, onset, and duration of plantar flexors, dorsiflexors, knee flexors, knee extensors, and hip stabilizers during the initial and late stages of rSTS. Before and after rSTS, we measured maximal voluntary isometric knee extension force, and rate of perceived exertion, which was also recorded during rSTS task.Results: Older vs. younger adults generated 35% lower maximum voluntary isometric knee extension force. During the initial stage of rSTS, older vs. younger adults activated the dorsiflexor 60% higher, all 5 muscle groups 37% longer, and the hip stabilizers 80% earlier. Older vs. younger adults completed 467 fewer STS trials and, at failure, their rate of perceived exertion was ~17 of 20 on the Borg scale. At the end of the rSTS, maximum voluntary isometric knee extension force decreased 16% similarly in older and younger, as well as the similar age groups decline in activation of the dorsiflexor and knee extensor muscles (all p < 0.05).Conclusion: By performing 467 fewer STS trials, older adults minimized the potential effects of fatigability on muscle activation, voluntary force, and motor function. Such a sparing effect may explain the minimal changes in gait after rSTS reported in previous studies, suggesting a limited scope of this perturbation model to probe age-effects on muscle adaptation in functional tasks.

scholarly journals History-Dependence of Muscle Excitation and Oxygenation During Isometric Knee Extension Force Production

2020 ◽  
Vol 29 (4) ◽  
pp. 385-393
Author(s):  
Junkyung Song ◽  
Kitae Kim ◽  
Sungjun Lee ◽  
Jiseop Lee ◽  
Jaebum Park
Keyword(s):  
Muscle Activation ◽  
Force Production ◽  
Time History ◽  
Knee Extension ◽  
Terminal Phase ◽  
History Dependence ◽  
Isometric Knee Extension ◽  
Extension Force ◽  
History Of ◽  
Four Levels

PURPOSE:This study examined the issue of history-dependence on muscle excitation and oxygenation by using surface electromyography (EMG) and near-infrared spectroscopy (NIRS).METHODS: Eight male participants performed isometric knee extension force production tasks that started at four levels of initial force production (30, 40, 60, 70% of maximal voluntary contraction, MVC) and commonly converged to the production of 50% of MVC by increasing or decreasing knee extension forces. We quantified the integrated electromyogram (iEMG), total hemoglobin (tHb), and the desaturation rate of muscle tissue (TSI<sub>SLOPE</sub>) of the vastus lateralis and compared the differences in the quantified variables between the experimental conditions.RESULTS: For the four levels of initial forces production, all the variables showed significant linear relationships with outcome forces. However, the magnitudes of the variables were varied depending on the contraction history at the terminal phase where the identical level of force production (50% of MVC) was required. At the terminal phase, the iEMG was affected by the time history of both mode (e.g., increment or decrement) and magnitude (e.g., 10% or 20% change of MVC), while the tHb and TSI<sub>SLOPE</sub> showed significant differences between the time history of mode only.CONCLUSIONS:The main result of the current study demonstrates the history-dependence of the changes in physiological demands in muscle activation. In particular, the indices of muscle excitation and oxygenation at the same level of force were varied depending on the time history of contraction, which implies the indices of muscle excitation and oxygenation may not be invariant component to specify the levels of outcome forces.

scholarly journals Isometric knee extension force in Japanese type 2 diabetic patients without apparent diabetic polyneuropathy: Data from the Multicenter Survey of the Isometric Lower Extremity Strength in Type 2 Diabetes study

2019 ◽  
Vol 7 ◽  
pp. 205031211882341 ◽  
Author(s):  
Takuo Nomura ◽  
Tomoyasu Ishiguro ◽  
Masayoshi Ohira ◽  
Hiroyuki Oka ◽  
Yukio Ikeda
Keyword(s):  
Type 2 Diabetes ◽  
Diabetic Polyneuropathy ◽  
Knee Extension ◽  
Diabetic Patients ◽  
Control Subjects ◽  
Multicenter Survey ◽  
Isometric Knee Extension ◽  
Extension Force ◽  
Healthy Control

Objectives: To determine standard reference values for isometric knee extension force using a cohort of Japanese type 2 diabetic patients without diabetic polyneuropathy. Methods: Patient data were collected from the Multicenter Survey of the Isometric Lower Extremity Strength in Type 2 Diabetes study and compared with previously published data of healthy control subjects. In total, we enrolled 898 patients with type 2 diabetes aged 30–87 years, who did not have diabetic polyneuropathy. The control group included 510 healthy subjects aged 30–88 years. Maximum isometric knee extension force (KEF) values were obtained by using a hand-held dynamometer with belt stabilization. In addition, KEF (kgf) was adjusted for bodyweight (kg) to calculate %KEF. Results: KEF and %KEF decreased with age in both patients with diabetes and healthy control subjects. The mean values of KEF and %KEF in patients with diabetes were reduced by 9.7% and 20.8%, respectively, in males, and by 11.6% and 23.0%, respectively, in females compared to the values in healthy control subjects. Conclusion: KEF and %KEF in patients with type 2 diabetes without diabetic polyneuropathy may reduce by approximately 10% and 20%, respectively, compared to these values in healthy control subjects. This study provides reference values for isometric KEF with respect to sex in a population covering a wide age range.

Isometric knee extension force measured using a handheld dynamometer with and without belt-stabilization

2011 ◽  
Vol 28 (7) ◽  
pp. 562-568 ◽  
Author(s):  
Richard W Bohannon ◽  
Jeffrey Kindig ◽  
Gregory Sabo ◽  
Allison E Duni ◽  
Peter Cram
Keyword(s):  
Knee Extension ◽  
Isometric Knee Extension ◽  
Extension Force

scholarly journals Feed-forward regulation of self-selected exercise intensity in response to different rates of arterial deoxygenation

2017 ◽  
Vol 42 (1) ◽  
pp. 88-88
Author(s):  
Saro D. Farra
Keyword(s):  
Exercise Intensity ◽  
Exercise Performance ◽  
Perceived Exertion ◽  
Knee Extension ◽  
Rate Of Change ◽  
Dependent Manner ◽  
Target Time ◽  
Arterial Blood ◽  
Arterial Desaturation ◽  
Isometric Knee Extension

Arterial desaturation impairs exercise performance in a dose-dependent manner. However, new theories of exercise-induced fatigue suggest that increasing rates of arterial deoxygenation augment the fatigue response during exercise. The purpose of this dissertation is to clarify if self-selected exercise intensity, while exercising at a constant rate of perceived exertion (RPE), is sensitive to alterations in the absolute arterial saturation (SPO2) and/or the rate of change in SPO2. Subjects performed constant RPE exercise for 30 min. They were instructed to adjust their exercise intensity during the trial to maintain their RPE at 5 on Borg’s 10-point scale. Subjects engaged in continuous bilateral, isokinetic cycling and intermittent, unilateral, isometric knee-extension. The fraction of inspired oxygen was reduced to desaturate arterial blood from starting values (>98%) to 70%. This desaturation occurred linearly over 3 target time periods (FAST, 5 min; MED, 15 min; SLOW, 25 min). The rate of arterial desaturation was significantly different between each of the 3 conditions. During cycling exercise, PO (FAST = 2.8 ± 2.1 W·% SPO2−1; MED = 2.5 ± 1.8 W·% SPO2−1; SLOW = 1.8 ± 1.6 W·% SPO2−1; P < 0.001) and surface electromyography (sEMG) of the vastus medialis (FAST = 1.3 ± 0.6%·% SPO2−1; MED = 1.1 ± 0.5%·% SPO2−1; SLOW = 0.7 ± 0.7%·% SPO2−1; P < 0.001) decreased at significantly different rates. Post hoc comparisons revealed that the rates of decline in PO and sEMG during FAST and MED were similar, and both were greater than SLOW. However, during isometric knee extension exercise, the level of force production and sEMG remained similar across saturation levels. These results confirm that decreases in absolute SPO2 impair self-selected exercise intensity and that faster desaturation rates magnify that impairment, but only when a large muscle mass is engaged. These findings suggest that the rate of arterial deoxygenation independently influences exercise performance and that the central depressant effect may be a function of the metabolic strain associated with hypoxia, rather than the hypoxia per se.

scholarly journals Rate of Muscle Activation in Power-and Endurance-Trained Boys

2011 ◽  
Vol 6 (1) ◽  
pp. 94-105 ◽  
Author(s):  
Cameron Mitchell ◽  
Rotem Cohen ◽  
Raffy Dotan ◽  
David Gabriel ◽  
Panagiota Klentrou ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Peak Torque ◽  
Surface Emg ◽  
Knee Extension ◽  
Endurance Athletes ◽  
Group Differences ◽  
Electromechanical Delay ◽  
Cross Sectional ◽  
Isometric Knee Extension ◽  
Muscle Cross Sectional Area

Previous studies in adults have demonstrated power athletes as having greater muscle force and muscle activation than nonathletes. Findings on endurance athletes are scarce and inconsistent. No comparable data on child athletes exist.Purpose:This study compared peak torque (Tq), peak rate of torque development (RTD), and rate of muscle activation (EMG rise, Q30), in isometric knee extension (KE) and fexion (KF), in pre- and early-pubertal power- and endurance-trained boys vs minimally active nonathletes.Methods:Nine gymnasts, 12 swimmers, and 18 nonathletes (7–12 y), performed fast, maximal isometric KE and KF. Values for Tq, RTD, electromechanical delay (EMD), and Q30 were calculated from averaged torque and surface EMG traces.Results:No group differences were observed in Tq, normalized for muscle cross-sectional area. The Tq-normalized KE RTD was highest in power athletes (6.2 ± 1.9, 4.7 ± 1.2, 5.0 ± 1.5 N·m·s–1, for power, endurance, and nonathletes, respectively), whereas no group differences were observed for KF. The KE Q30 was significantly greater in power athletes, both in absolute terms and relative to peak EMG amplitude (9.8 ± 7.0, 5.9 ± 4.2, 4.4 ± 2.2 mV·ms and 1.7 ± 0.8, 1.1 ± 0.6, 0.9 ± 0.5 (mV·ms)/(mV) for power, endurance, and nonathletes, respectively), with no group differences in KF. The KE EMD tended to be shorter (P = .07) in power athletes during KE (71.0 ± 24.1, 87.8 ± 18.0, 88.4 ± 27.8 ms, for power, endurance, and nonathletes), with no group differences in KF.Conclusions:Pre- and early-pubertal power athletes have enhanced rate of muscle activation in specifically trained muscles compared with controls or endurance athletes, suggesting that specific training can result in muscle activation-pattern changes before the onset of puberty.

Predictability of maximum voluntary isometric knee extension force from submaximal contractions in older adults

2002 ◽  
Vol 27 (1) ◽  
pp. 40-45 ◽  
Author(s):  
Scott K. Stackhouse ◽  
Jennifer E. Stevens ◽  
Christopher D. Johnson ◽  
Lynn Snyder-Mackler ◽  
Stuart A. Binder-Macleod
Keyword(s):  
Older Adults ◽  
Knee Extension ◽  
Isometric Knee Extension ◽  
Extension Force

scholarly journals Training History-Dependent Functional Role of EMG Model-Predicted Antagonist Moments in Knee Extensor Moment Generation in Healthy Young Adults

Biomechanics ◽  
2022 ◽  
Vol 2 (1) ◽  
pp. 7-19
Author(s):  
Tibor Hortobágyi ◽  
Paul DeVita ◽  
Robert Brady ◽  
Patrick Rider
Keyword(s):  
Muscle Activation ◽  
Knee Extensor ◽  
Knee Extension ◽  
Younger Adults ◽  
Antagonist Muscle ◽  
Functional Roles ◽  
Leg Strength ◽  
Training History ◽  
Antagonist Coactivation

Resistance training (RT) improves the skeletal muscle’s ability to generate maximal voluntary force and is accompanied by changes in the activation of the antagonist muscle which is not targeted primarily by RT. However, the nature and role of neural adaptation to RT in the antagonist muscle is paradoxical and not well understood. We compared moments, agonist muscle activation, antagonist activation, agonist-antagonist coactivation, and electromyographic (EMG) model-predicted moments generated by antagonist hamstring muscle coactivation during isokinetic knee extension in leg strength-trained (n = 10) and untrained (n = 11) healthy, younger adults. Trained vs. untrained adults were up to 58% stronger. During knee extension, hamstring activation was 1.6-fold greater in trained vs. untrained adults (p = 0.022). This hamstring activation produced 2.6-fold greater model-predicted antagonist moments during knee extension in the trained (42.7 ± 19.55 Nm) vs. untrained group (16.4 ± 12.18 Nm; p = 0.004), which counteracted (reduced) quadriceps knee extensor moments ~43 Nm (0.54 Nm·kg−1) and by ~16 Nm (0.25 Nm·kg−1) in trained vs. untrained. Antagonist hamstring coactivation correlated with decreases and increases, respectively, in quadriceps moments in trained and untrained. The EMG model-predicted antagonist moments revealed training history-dependent functional roles in knee extensor moment generation.

Longer Integration Intervals Reduce Variability and Improve Reliability of EMG Derived from Maximal Isometric Exertions

1999 ◽  
Vol 15 (2) ◽  
pp. 210-220 ◽  
Author(s):  
Peter F. Vint ◽  
Richard N. Hinrichs
Keyword(s):  
Vastus Lateralis ◽  
Knee Extension ◽  
Vastus Lateralis Muscle ◽  
Electromechanical Delay ◽  
Integration Interval ◽  
Isometric Knee Extension ◽  
Extension Force ◽  
Maximum Effort ◽  
Integrated Emg ◽  
Force Relationship

Isometric knee extension force and average integrated EMG of the vastus lateralis muscle were obtained from 27 healthy subjects using a maximum effort, ramp and hold protocol. In each of the 125 total trials mat were included in the analysis, a 2-s plateau region was extracted and divided into two adjacent 1000-ms bins. Variability and reliability of bin-to-bin measurements of force and EMG were then evaluated across 14 different integration intervals ranging from 10 to 1000 ms. Statistical analyses of bin-to-bin variability measures demonstrated that integration intervals of 250 ms and longer significantly reduced variability and improved reliability of average integrated EMG values during maximum effort isometric exertions. Bin-to-bin EMG reliability increased from .728 at 10 ms to .991 at 1000 ms. Force parameters appeared less sensitive to changes in length of the integration interval. It was suggested that longer intervals might also improve the validity of the EMG-force relationship during maximum effort isometric exertions by reducing problems associated with electromechanical delay.

MUSCLE QUALITY IMPROVES WITH EXTENDED HIGH-INTENSITY RESISTANCE TRAINING AFTER HIP FRACTURE

2017 ◽  
pp. 1-6
Author(s):  
R.A. BRIGGS ◽  
J.R. HOUCK ◽  
M.J. DRUMMOND ◽  
J.M. FRITZ ◽  
P.C. LASTAYO ◽  
...  
Keyword(s):  
Hip Fracture ◽  
Resistance Training ◽  
Physical Function ◽  
Muscle Mass ◽  
High Intensity ◽  
Knee Extension ◽  
Muscle Quality ◽  
Isometric Knee Extension ◽  
Before And After ◽  
Extension Force

Background: Muscle mass deficits endure after hip fracture. Strategies to improve muscle quality may improve mobility and physical function. It is unknown whether training after usual care yields muscle quality gains after hip fracture. Objectives: To determine whether muscle quality improves after hip fracture with high-intensity resistance training and protein supplementation. Design: Case series. Setting: University of Utah Skeletal Muscle Exercise Research Facility. Participants: 17 community-dwelling older adults, 3.6+/-1.1 months post-hip fracture, recently discharged from usual-care physical therapy (mean age 77.0+/-12.0 years, 12 female), enrolled. Intervention: Participants underwent 12 weeks (3x/week) of unilaterally-biased resistance training. Methods/Materials: Participants were measured via a 3.0 Tesla whole-body MR imager for muscle lean and intramuscular adipose tissue (IMAT) of the quadriceps before and after resistance training. Peak isometric knee extension force output was measured with an isokinetic dynamometer. Muscle quality was calculated by dividing peak isometric knee extension force (N) by quadriceps lean muscle mass (cm2). In addition, common physical function variables were measured before and after training. Results: Surgical and nonsurgical lean quadriceps muscle mass improved among participants (mean change: 2.9 cm2+/-1.4 cm2, and 2.7 cm2+/-1.3 cm2, respectively), while IMAT remained unchanged. Peak force improved in the surgical limb by 43.1+/-23N, with no significant change in the nonsurgical limb. Significant gains in physical function were evident after training. Conclusion: Participants recovering from hip fracture demonstrated improvements in muscle mass, muscle strength, and muscle quality in the surgical limb after hip fracture. These were in addition to gains made in the first months after fracture with traditional care. Future studies should determine the impact that muscle quality has on long-term functional recovery in this population.

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