scholarly journals Short-Term Effects of Suspension Training on Strength and Power Performances

2018 ◽  
Vol 3 (4) ◽  
pp. 51 ◽  
Author(s):  
Giuseppe Giancotti ◽  
Andrea Fusco ◽  
Alice Iannaccone ◽  
Cristina Cortis
Keyword(s):  
Repeated Measures ◽  
Maximum Voluntary Contraction ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Experimental Session ◽  
Limited Information ◽  
Acute Responses ◽  
Muscle Activations ◽  
The Individual ◽  
Squat Jumps

Suspension Training (ST) workouts include a variety of movements requiring the individual to maintain balance while performing various resistance exercises in an interval fashion. Although ST is thought to elicit higher muscle activations than traditional exercises, only limited information is available on its acute effects on strength and power performances, especially in relation to gender. Therefore, the purpose of this study was to evaluate the strength and power acute responses after ST, also in relation to gender. Eighty-eight (46 males, 42 females) participants were administered countermovement jumps (CMJ), squat jumps (SJ), lower limb Maximum Voluntary Contraction (MVC) at 90° angle knee extension, and grip strength (handgrip) before (PRE) and after (POST) a 50 min ST session involving upper, lower body and core exercises. ANOVA for repeated measures was used to evaluate the differences (p < 0.05) in relation to gender and experimental session. After ST session, significantly higher values emerged in males, whereas no significant changes were found in females. Findings indicate that ST as a form of exercise is useful to maintain and improve acute strength and power performances, especially in male participants. Future studies should be carried out to explore the gender-related differences in response to acute bout of ST exercises.

A Comparison of Knee-Extension Torque Production with Biphasic versus Russian Current

2000 ◽  
Vol 9 (3) ◽  
pp. 229-239 ◽  
Author(s):  
William R. Holcomb ◽  
Shahin Golestani ◽  
Shante Hill
Keyword(s):  
Athletic Training ◽  
High Intensity ◽  
Repeated Measures ◽  
Outcome Measure ◽  
Maximum Voluntary Contraction ◽  
Neuromuscular Electrical Stimulation ◽  
Strength Loss ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Main Outcome Measure

Context:Neuromuscular electrical stimulation (NMES) can be used to prevent the atrophy and strength loss associated with immobilization.Objective:To compare the effects of biphasic current and the modulated “Russian” current on muscular torque production during different contraction conditions.Design, Setting, and Participants:In a within-subjects design, 10 healthy subjects in an athletic training laboratory received NMES.Interventions:Isometric knee-extension torque was recorded with the Biodex™ under 4 conditions: maximum voluntary contraction (MVC; control), MVC superimposed with low-intensity stimulation (sham), MVC superimposed with high-intensity stimulation, and high-intensity stimulation only.Main Outcome Measure:Data normalized for body weight were analyzed using a 2 (current type) X 4 (condition) repeated-measures analysis of variance.Results:The main effect for current type was not significant, F1,9 = .03, P = .87.

Self–Myofascial Release: No Improvement of Functional Outcomes in “Tight” Hamstrings

2016 ◽  
Vol 11 (5) ◽  
pp. 658-663 ◽  
Author(s):  
Robert W. Morton ◽  
Sara Y. Oikawa ◽  
Stuart M. Phillips ◽  
Michaela C. Devries ◽  
Cameron J. Mitchell
Keyword(s):  
Maximum Voluntary Contraction ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Muscle Stiffness ◽  
Therapeutic Modality ◽  
Myofascial Release ◽  
Joint Range Of Motion ◽  
Joint Range ◽  
Torque Development

Purpose:Self–myofascial release (SMR) is a common exercise and therapeutic modality shown to induce acute improvements in joint range of motion (ROM) and recovery; however, no long-term studies have been conducted. Static stretching (SS) is the most common method used to increase joint ROM and decrease muscle stiffness. It was hypothesized that SMR paired with SS (SMR+SS) compared with SS alone over a 4-wk intervention would yield greater improvement in knee-extension ROM and hamstring stiffness.Methods:19 men (22 ± 3 y) with bilateral reduced hamstring ROM had each of their legs randomly assigned to either an SMR+SS or an SS-only group. The intervention consisted of 4 repetitions of SS each for 45 s or the identical amount of SS preceded by 4 repetitions of SMR each for 60 s and was performed on the respective leg twice daily for 4 wk. Passive ROM, hamstring stiffness, rate of torque development (RTD), and maximum voluntary contraction (MVC) were assessed pre- and postintervention.Results:Passive ROM (P < .001), RTD, and MVC (P < .05) all increased after the intervention. Hamstring stiffness toward end-ROM was reduced postintervention (P = .02). There were no differences between the intervention groups for any variable.Conclusion:The addition of SMR to SS did not enhance the efficacy of SS alone. SS increases joint ROM through a combination of decreased muscle stiffness and increased stretch tolerance.

scholarly journals Increased Voluntary Activation of the Elbow Flexors Following a Single Session of Spinal Manipulation in a Subclinical Neck Pain Population

2019 ◽  
Vol 9 (6) ◽  
pp. 136 ◽  
Author(s):  
Mat Kingett ◽  
Kelly Holt ◽  
Imran Khan Niazi ◽  
Rasmus Wiberg Nedergaard ◽  
Michael Lee ◽  
...  
Keyword(s):  
Neck Pain ◽  
Repeated Measures ◽  
Spinal Manipulation ◽  
Maximum Voluntary Contraction ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Elbow Flexors ◽  
Single Session ◽  
Post Intervention

To investigate the effects of a single session of spinal manipulation (SM) on voluntary activation of the elbow flexors in participants with subclinical neck pain using an interpolated twitch technique with transcranial magnetic stimulation (TMS), eighteen volunteers with subclinical neck pain participated in this randomized crossover trial. TMS was delivered during elbow flexion contractions at 50%, 75% and 100% of maximum voluntary contraction (MVC) before and after SM or control intervention. The amplitude of the superimposed twitches evoked during voluntary contractions was recorded and voluntary activation was calculated using a regression analysis. Dependent variables were analyzed with two-way (intervention × time) repeated measures ANOVAs. Significant intervention effects for SM compared to passive movement control were observed for elbow flexion MVC (p = 0.04), the amplitude of superimposed twitch (p = 0.04), and voluntary activation of elbow flexors (p =0.03). Significant within-group post-intervention changes were observed for the superimposed twitch (mean group decrease of 20.9%, p < 0.01) and voluntary activation (mean group increase of 3.0%, p < 0.01) following SM. No other significant within-group changes were observed. Voluntary activation of the elbow flexors increased immediately after one session of spinal manipulation in participants with subclinical neck pain. A decrease in the amplitude of superimposed twitch during elbow flexion MVC following spinal manipulation suggests a facilitation of motor cortical output.

scholarly journals Post-Activation Potentiation and Fatigue of Quadriceps Muscle after Continuous Isometric Contractions at Maximal and Submaximal Intensities

2018 ◽  
Vol 4 (67) ◽  
Author(s):  
Nerijus Masiulis ◽  
Albertas Skurvydas ◽  
Sigitas Kamandulis ◽  
Jūratė Kudirkaitė ◽  
Vytautas Sukockas ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Recovery Period ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Contractile Properties ◽  
Contraction Time ◽  
Isometric Knee Extension

The dominance of fatigue or post-activation potentiation (PAP) depends on the type, intensity, and duration of exercise and duration of the recovery before contractility is tested. Although the decrease in PAP magnitude with decreased exercise intensity is well documented (Vandervoort et al., 1983; Behm et al., 2004), it is not clear how PAP and fatigue influences the contractile properties of skeletal muscle when exercise is of different intensity but with the same amount of work performed. Thus it is important to understand the manifestation of PAP and fatigue of skeletal muscle after continuous maximal and submaximal contractions but with the same amount of work performed. Eight healthy untrained men (age 23—27 years, mass 83.5 ± 5.4 kg) performed maximal sustained isometric knee extension for 30 s (MVC-30 s) and on the other occasion the same subject performed sustained isometric knee extension for 60 s at 50% of maximal (50% MVC-60 s). We assumed that the amount of performed work was the same during both MVC-30 s and 50% MVC-60 s exercises. The experimental order was randomized. The contractile properties of quadriceps muscle evoked by electrical stimulation at 1 Hz (P 1), 10 Hz (P 10), 20 Hz (P 20), and 50 Hz (P 50) as well as contraction time (CT) and relaxation time (RT) of single twitch (P 1) and EMGrms of v. lateralis muscle were recorded before and immediately after the exercises (0 min) and 1, 2, and 3 min following the exercises. A significantly greater potentiation (p < 0.05) of P1 was observed after 30-s MVC (MVC-30 s) compared with the 60-s MVC (50% MVC-60 s) immediately after exercise and at 1 min of recovery. No changes in P 1 contraction time (CT) were observed during 3 min recovery period, however half relaxation of P 1 (½ RT) was more prolonged (p < 0.05) immediately after 50% MVC-60 s exercises. Moreover, immediately and 1 min post exercise the P 10 force after MVC-30 s exercise was higher (p < 0.05) compared to 50% MVC-60 s exercise. No differences between MVC-30 s and 50% MVC-60 s exercises were observed at high stimulation frequencies, maximal voluntary contraction force (MVC) as well as for EMGrms values during 3 min recovery period. The main finding of the present study was that PAP was observed after both maximal and submaximal intensity exercises when the same amount of work was performed. The more intensively exercise is performed, the more PAP offsets fatigue straight after exercise (maximal intensity); while after submaximal exercise PAP becomes more evident only during the recovery period.Keywords: skeletal muscle, isometric exercise, maximum voluntary contraction, recovery.

scholarly journals The Reliability of Electromyographic Normalization Methods for Cycling Analyses

2015 ◽  
Vol 46 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Jonathan Sinclair ◽  
Paul John Taylor ◽  
Jack Hebron ◽  
Darrell Brooks ◽  
Howard Thomas Hurst ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Maximum Voluntary Contraction ◽  
Body Height ◽  
Reference Value ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Voluntary Contraction ◽  
Value Differences ◽  
Emg Amplitude ◽  
S Cycling

AbstractElectromyography (EMG) is normalized in relation to a reference maximum voluntary contraction (MVC) value. Different normalization techniques are available but the most reliable method for cycling movements is unknown. This study investigated the reliability of different normalization techniques for cycling analyses. Twenty-five male cyclists (age 24.13 ± 2.79 years, body height 176.22 ± 4.87 cm and body mass 67.23 ± 4.19 kg, BMI = 21.70 ± 2.60 kg·m−1) performed different normalization procedures on two occasions, within the same testing session. The rectus femoris, biceps femoris, gastrocnemius and tibialis anterior muscles were examined. Participants performed isometric normalizations (IMVC) using an isokinetic dynamometer. Five minutes of submaximal cycling (180 W) were also undertaken, allowing the mean (DMA) and peak (PDA) activation from each muscle to serve as reference values. Finally, a 10 s cycling sprint (MxDA) trial was undertaken and the highest activation from each muscle was used as the reference value. Differences between reference EMG amplitude, as a function of normalization technique and time, were examined using repeated measures ANOVAs. The testretest reliability of each technique was also examined using linear regression, intraclass correlations and Cronbach’s alpha. The results showed that EMG amplitude differed significantly between normalization techniques for all muscles, with the IMVC and MxDA methods demonstrating the highest amplitudes. The highest levels of reliability were observed for the PDA technique for all muscles; therefore, our results support the utilization of this method for cycling analyses.

scholarly journals Flavanol-Rich Cacao Mucilage Juice Enhances Recovery of Power but Not Strength from Intensive Exercise in Healthy, Young Men

Sports ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 159 ◽  
Author(s):  
Paul Morgan ◽  
Paola Wollman ◽  
Sarah Jackman ◽  
Joanna Bowtell
Keyword(s):  
Venous Blood ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Post Exercise ◽  
Intensive Exercise ◽  
Counter Movement Jump ◽  
Knee Extension Exercise ◽  
Time Point

(1) Background: Mucilage within cacao pods contains high levels of polyphenols. We investigated whether consumption of cacao juice enhances the recovery of muscle function following intensive knee extension exercise. (2) Methods: Ten recreationally active males completed two trials of 10 sets of 10 single leg knee extensions at ~80% one repetition maximum. Participants consumed each supplement (ZumoCacao® juice, CJ or a dextrose drink, PL) for 7 days prior to and 48 h post exercise. Knee extension maximum voluntary contraction (MVC) and a counter movement jump (CMJ) were performed at baseline, immediately, 24 h, and 48 h post-exercise. Venous blood samples were collected at each time point and analyzed for indices of inflammation, oxidative damage, and muscle damage. (3) Results: CMJ height recovered faster with CJ at 24 h and 48 h post-exercise (p < 0.05), but there was no effect of CJ on recovery of MVC (both p > 0.05). There was also no effect of the trial on any blood markers (all p > 0.05). (4) Conclusions: Supplementation with CJ for 7 days prior to and 2 days after intensive knee extensor exercise improved functional recovery as shown by an improved recovery of CMJ up to 48 h post-exercise. However, the precise mechanism of action is unclear and requires further investigation.

Two heads are better than one: both complementary and synchronous strategies facilitate joint action

2013 ◽  
Vol 109 (5) ◽  
pp. 1307-1314 ◽  
Author(s):  
Junya Masumoto ◽  
Nobuyuki Inui
Keyword(s):  
Joint Action ◽  
Maximum Voluntary Contraction ◽  
Absolute Error ◽  
Voluntary Contraction ◽  
Phase Region ◽  
Total Force ◽  
Individual Action ◽  
New Findings ◽  
The Individual ◽  
The Right

If two people lift and carry an object, they not only produce complementary forces on the object but also walk in synchrony. Previous studies have not examined how two types of coordination strategy are adopted simultaneously. The present study thus tested the hypothesis that complementary and synchronous strategies simultaneously facilitate the action coordination performed by two people. Ten pairs of participants produced periodic isometric forces such that the sum of forces they produced was the target force cycling between 5% and 10% of maximum voluntary contraction with an interval of 1,000 ms (joint action), while individuals alone produced the same target forces with the right hand (individual action). The correlation between forces produced by two participants was highly negative when the total force was visible, indicating that the two participants produced complementary forces. When the image of the total or partner force was presented, the coherence between force-time series produced by two participants was highest at 1 Hz. The relative phase angles were also distributed at the 0–20° phase region. These innovative findings indicate that two participants simultaneously adopted both complementary and temporal synchronous strategies exclusively when the total force was visible. With the vision of total force, surprisingly, while the joint action exhibited a less variable force than the individual action, the joint action exhibited a smaller absolute error of forces than the individual action. These new findings indicated that the joint action controlled force more accurately than the individual action.

Skin Cooling Alters the Activation Patterns of Different Heads of the Quadriceps

2005 ◽  
Vol 30 (2) ◽  
pp. 127-139 ◽  
Author(s):  
Ryuta Kinugasa ◽  
Kazumasa Yoshida ◽  
Takayuki Watanabe ◽  
Kousuke Kuchiki ◽  
Akira Horii
Keyword(s):  
Isometric Force ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Transverse Relaxation Time ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Activation Patterns ◽  
Skin Cooling ◽  
The Right

The purpose of this study was to examine the effect of selective skin cooling over m. vastus lateralis (VL) on the activation patterns of quadriceps femoris muscle during knee extension exercise (KEE) using muscle function magnetic resonance imaging (mfMRI). The isometric force production of the right thigh was tested in 7 healthy young men at maximum voluntary contraction (MVC), and the transverse relaxation time (T2) value was taken from mfMR images at rest and immediately after KEE with 4 sets of 10 repetitions at a load equal to 60% of their 10-rep maximum, with and without skin cooling. The cooling was carried out by ice pack on the surface of the skin of the VL for 3 min before resting mfMRI and MVC tests, and before KEE, during KEE, and during the KEE rest intervals. The percent change in T2 of the m. vastus intermedius was significantly increased by skin cooling in comparison to the change without skin cooling, p < 0.05. This result suggests that skin cooling alters the activation pattern of the different heads of the quadriceps. Key words: cold, mfMRI, synergy, recruitment, neuromuscular plasticity

Force control of quadriceps muscle is bilaterally impaired in subacute stroke

2011 ◽  
Vol 111 (5) ◽  
pp. 1290-1295 ◽  
Author(s):  
John W. Chow ◽  
Dobrivoje S. Stokic
Keyword(s):  
Force Control ◽  
Maximum Voluntary Contraction ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Force Variability ◽  
Stroke Patients ◽  
Subacute Stroke ◽  
Peak Knee ◽  
Isometric Knee Extension

We tested the hypothesis that force variability and error during maintenance of submaximal isometric knee extension are greater in subacute stroke patients than in controls and are related to motor impairments. Contralesional (more-affected) and ipsilesional (less-affected) legs of 33 stroke patients with sufficiently high motor abilities (62 ± 13 yr, 16 ± 2 days postinjury) and the dominant leg of 20 controls (62 ± 10 yr) were tested in sitting position. After peak knee extension torque [maximum voluntary contraction (MVC)] was established, subjects maintained 10, 20, 30, and 50% of MVC as steady and accurate as possible for 10 s by matching voluntary force to the target level displayed on a monitor. Coefficient of variation (CV) and root-mean-square error (RMSE) were used to quantify force variability and error, respectively. The MVC was significantly smaller in the more-affected than less-affected leg, and both were significantly lower than in controls. The CV was significantly larger in the more-affected than less-affected leg at 20 and 50% MVC, whereas both were significantly larger compared with controls across all force levels. Both more-affected and less-affected legs of patients showed significantly greater RMSE than controls at 30 and 50% MVC. The CV and RMSE were not related to the Fugl-Meyer motor score or to the Rivermead Mobility Index. The CV negatively correlated with MVC in controls but only in the less-affected leg of patients. It is concluded that isometric knee extension strength and force control are bilaterally impaired soon after stroke but more so in the more-affected leg. Future studies should examine possible mechanisms and the evolution of these changes.

scholarly journals Comparison of Upper Extremity Muscle Activation Levels Between Isometric and Dynamic Maximum Voluntary Contraction Protocols

2019 ◽  
Vol 7 (2) ◽  
pp. 21 ◽  
Author(s):  
Ben Warnock ◽  
Danielle L. Gyemi ◽  
Evan Brydges ◽  
Jennifer M. Stefanczyk ◽  
Charles Kahelin ◽  
...  
Keyword(s):  
Upper Extremity ◽  
Muscle Activation ◽  
Full Range ◽  
Maximum Voluntary Contraction ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Elastic Band ◽  
Muscle Activations ◽  
Voluntary Contractions ◽  
Flexion And Extension

Background: Muscle activations (MA) during maximum voluntary contractions (MVC) are commonly utilized to normalize muscle contributions. Isometric MVC protocols may not activate muscles to the same extent as during dynamic activities, such as falls on outstretched hands (FOOSH), that can occur during sport or recreational activities. Objective: The purpose of this study was to compare the peak MA of upper extremity muscles during isometric and dynamic MVC protocols. Methods: Twenty-four (12 M, 12 F) university-aged participants executed wrist and elbow flexion and extension actions during five-second MVC protocols targeting six upper extremity muscles (three flexors and three extensors). Each protocol [isometric (ISO); dynamic (eccentric (ECC), concentric (CON), elastic band (ELAS), un-resisted (UNRES)] consisted of three contractions (with one-minute rest periods between) during two sessions separated by one week. Muscle activation levels were collected using standard electromyography (EMG) preparations, electrode placements and equipment reported previously. Results: Overall, the ECC and CON dynamic protocols consistently elicited higher peak muscle activation levels than the ISO protocol for both males and females during both sessions. Over 95% of the CON trials resulted in mean and peak muscle activation ratios greater than ISO, with 56.3% being significantly greater than ISO (p < 0.05). Conclusion: Higher activation levels can be elicited in upper extremity muscles when resistance is applied dynamically through a full range of motion during MVC protocols.

Sign in / Sign up

Export Citation Format

Share Document