scholarly journals Investigation of Inter-Limb Symmetry in Knee Extensors Using Different Strength Outcome Measures

Diagnostics ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1882
Author(s):  
Darjan Smajla ◽  
Jure Žitnik ◽  
Nejc Šarabon
Keyword(s):  
Regression Line ◽  
Knee Extension ◽  
Cross Sectional Study ◽  
Voluntary Contraction ◽  
Muscle Performance ◽  
Knee Extensors ◽  
Strong Correlations ◽  
Cross Sectional ◽  
Isokinetic Torque ◽  
Leg Dominance

Muscle performance between contra-lateral knee extensors is most often assessed using maximal test for isometric/isokinetic torque evaluation. Recently, the rate of force development scaling factor (RFD-SF) has been used to evaluate neuromuscular capacity with a range of submaximal target peak torques, which could highlight other aspects of inter-limb (a)symmetry. The aim of our study was to investigate the differences, associations, and agreement between inter-limb symmetries of knee extensors using maximal torque (Tmax) rate of torque development (RTD), slope of the RFD-SF regression line (k), and theoretical peak of RTD (TPRTD). A total of 236 young, healthy athletes participated in the cross-sectional study. All participants performed unilateral knee extension (maximal voluntary contraction protocol and RFD-SF protocol) with both legs in the isometric knee dynamometer. Inter-limb symmetries were calculated for each outcome measure. Our results showed significant differences between all symmetry values (Tmax (91.7%), RTD (85.2%), k (94.2%), TPRTD (95.9%)). Significant strong correlations were found between symmetry values calculated from k and TPRTD (r = 0.88, p < 0.001), while weak correlation was found between Tmax and RTD (r = 0.17, p < 0.01. Fair agreement regarding leg dominance was found between Tmax and RTD values. Our results suggest that inter-limb (a)symmetries are metric- and task-specific.

scholarly journals Regional and muscle-specific adaptations in knee extensor hypertrophy using flywheel versus conventional weight-stack resistance exercise

2019 ◽  
Vol 44 (8) ◽  
pp. 827-833 ◽  
Author(s):  
Tommy R. Lundberg ◽  
Maria T. García-Gutiérrez ◽  
Mirko Mandić ◽  
Mats Lilja ◽  
Rodrigo Fernandez-Gonzalo
Keyword(s):  
Resistance Exercise ◽  
Muscle Hypertrophy ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Rectus Femoris ◽  
Knee Extension ◽  
Knee Extensors ◽  
Cross Sectional ◽  
Proximal Site ◽  
Before And After

This study compared the effects of the most frequently employed protocols of flywheel (FW) versus weight-stack (WS) resistance exercise (RE) on regional and muscle-specific adaptations of the knee extensors. Sixteen men (n = 8) and women (n = 8) performed 8 weeks (2–3 days/week) of knee extension RE employing FW technology on 1 leg (4 × 7 repetitions), while the contralateral leg performed regular WS training (4 × 8–12 repetitions). Maximal strength (1-repetition maximum (1RM) in WS) and peak FW power were determined before and after training for both legs. Partial muscle volume of vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), and rectus femoris (RF) were measured using magnetic resonance imaging. Additionally, quadriceps cross-sectional area was assessed at a proximal and a distal site. There were no differences (P > 0.05) between FW versus WS in muscle hypertrophy of the quadriceps femoris (8% vs. 9%), VL (10% vs. 11%), VM (6% vs. 8%), VI (5% vs. 5%), or RF (17% vs. 17%). Muscle hypertrophy tended (P = 0.09) to be greater at the distal compared with the proximal site, but there was no interaction with exercise method. Increases in 1RM and FW peak power were similar across legs, yet the increase in 1RM was greater in men (31%) than in women (20%). These findings suggest that FW and WS training induces comparable muscle-specific hypertrophy of the knee extensors. Given that these robust muscular adaptations were brought about with markedly fewer repetitions in the FW compared with WS, it seems FW training can be recommended as a particularly time-efficient exercise paradigm.

Autonomic, immunological and endocrine influences on adipose tissue as an organ

2021 ◽  
Vol 11 (3) ◽  
pp. 48-58
Author(s):  
Michael S Rahman ◽  
George P Einstein ◽  
Orien Tulp
Keyword(s):  
Adipose Tissue ◽  
Alternative Hypothesis ◽  
Health Centre ◽  
Cross Sectional Study ◽  
The Body ◽  
Physiological Data ◽  
Autonomous Nervous System ◽  
Strong Correlations ◽  
Cross Sectional ◽  
Multiple Variables

White Adipose Tissue (WAT) is typically regarded as a passive storage deposit of excess fat. However, recent research suggests that WAT behaves like an organ system that interacts with the autonomous nervous, endocrinological and immunological systems. Therefore, it is possible that WAT acts as a regulatory organ that keeps the body in homeostasis. This cross-sectional study uses physiological data from 30 patients at the Pinewood Natural Health Centre in Toronto, Canada to derive a description of the role of WAT in the mediation of homeostasis. Statistical methods derive a formula describing the dynamic congruence that contributes to a systems medicine (SM) understanding of the organism. Multiple variables including body parameters, composition, and metabolism, heart rate variability and the immune, autonomous, neural, and endocrinologicial systems were measured and correlated using multiple regression analysis. The null hypothesis was that no variables would correlate; the alternative hypothesis was that at least two variables that would correlate with each other to demonstrate congruence and order. This analysis found strong correlations with parameters of the immune system and metabolism and few correlations with the autonomous nervous system. This suggests that despite the body’s complexity, not all systems may contribute equally strongly to overall homeostasis

Force fluctuations are modulated by alternate muscle activity of knee extensor synergists during low-level sustained contraction

2004 ◽  
Vol 97 (6) ◽  
pp. 2121-2131 ◽  
Author(s):  
Motoki Kouzaki ◽  
Minoru Shinohara ◽  
Kei Masani ◽  
Tetsuo Fukunaga
Keyword(s):  
Correlation Coefficient ◽  
Muscle Activity ◽  
High Frequency ◽  
Vastus Lateralis ◽  
Frequency Component ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
High Frequency Component ◽  
Knee Extensors ◽  
Force Fluctuations

The study examined the hypothesis that altered synergistic activation of the knee extensors leads to cyclic modulation of the force fluctuations. To test this hypothesis, the force fluctuations were investigated during sustained knee extension at 2.5% of maximal voluntary contraction force for 60 min in 11 men. Surface electromyograms (EMG) were recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles. The SD of force and average EMG (AEMG) of each muscle were calculated for 30-s periods during alternate muscle activity. Power spectrum of force was calculated for the low- (≤3 Hz), middle- (4–6 Hz), and high-frequency (8–12 Hz) components. Alternate muscle activity was observed between RF and the set of VL and VM muscles. The SD of force was not constant but variable due to the alternate muscle activity. The SD was significantly greater during high RF activity compared with high VL and VM activity ( P < 0.05), and the correlation coefficient between the SD and AEMG was significantly greater in RF [0.736 (SD 0.095), P < 0.05] compared with VL and VM. Large changes were found in the high-frequency component. During high RF activity, the correlation coefficient between the SD and high-frequency component [0.832 (SD 0.087)] was significantly ( P < 0.05) greater compared with other frequency components. It is suggested that modulations in knee extension force fluctuations are caused by the unique muscle activity in RF during the alternate muscle activity, which augments the high-frequency component of the fluctuations.

Strength, Static Balance, Physical Activity, and Age Predict Maximal Gait Speed in Healthy Older Adults From a Rural Community: A Cross-Sectional Study

2015 ◽  
Vol 23 (4) ◽  
pp. 580-587 ◽  
Author(s):  
Silvia Aranda-García ◽  
Albert Busquets ◽  
Antoni Planas ◽  
Joan A. Prat-Subirana ◽  
Rosa M. Angulo-Barroso
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Rural Community ◽  
Gait Speed ◽  
Cross Sectional Study ◽  
Community Dwelling ◽  
Knee Extensors ◽  
Sectional Study ◽  
Cross Sectional ◽  
Physical Abilities

Purpose:Gait speed is related to physical function in older adults. This cross-sectional study examined the best predictors of maximal gait speed (MGS) among physical abilities, and general factors in healthy, rural community-dwelling older adults.Methods:MGS, muscle strength, and postural sway were measured in 55 community-dwelling participants (age, 72.1 ± 6.8, range 61–87 years; 72.7% women). Two stepwise regressions were used to find MGS predictors in two models: physical abilities and global.Results:Strength of knee extensors with 60° of knee flexion (KStrength60°) and maximal distance in the anterior-posterior direction with eyes closed explained 50.2% of MGS variance (p < .05) in the physical abilities model. KStrength60°, age, and level of physical activity explained 63.9% of MGS variance (p < .05) in the global model.Conclusions:Regardless of the model, KStrength60° was the best predictor of MGS in rural female older adults. Future research should examine the generalization of these findings to rural male older adults.

scholarly journals The influence of lower-limb dominance on postural balance

2011 ◽  
Vol 129 (6) ◽  
pp. 410-413 ◽  
Author(s):  
Angélica Castilho Alonso ◽  
Guilherme Carlos Brech ◽  
Andréia Moraes Bourquin ◽  
Julia Maria D'Andréa Greve
Keyword(s):  
Lower Limb ◽  
Postural Balance ◽  
Sensory Information ◽  
Cross Sectional Study ◽  
Balance Test ◽  
Cross Sectional ◽  
Balance System ◽  
Leg Dominance ◽  
Limb Dominance ◽  
Instability Indices

CONTEXT AND OBJECTIVE: Maintainance of postural balance requires detection of body movements, integration of sensory information in the central nervous system and an appropriate motor response. The purpose of this study was to evaluate whether lower-limb dominance has an influence on postural balance. DESIGN AND SETTING: This was a cross-sectional study conducted at Faculdade de Medicina da Universidade de São Paulo (FMUSP) and at Hospital do Coração (HCor). METHODS: Forty healthy sedentary males aged 20 to 40 years, without any injuries, were evaluated. A single-foot balance test was carried out using the Biodex Balance System equipment, comparing the dominant leg with the nondominant leg of the same individual. The instability protocols used were level 8 (more stable) and level 2 (less stable), and three instability indices were calculated: anteroposterior, mediolateral and general. RESULTS: The volunteers' mean age was 26 ± 5 years (range: 20-38), mean weight 72.3 ± 11 kg (range: 46-107) and mean height 176 ± 6 cm (range: 169-186). Thirty-four of them (85%) presented right-leg dominance (defined according to which leg they used for kicking) and six (15%) had left-leg dominance. There were no significant differences between the dominant and nondominant legs at the two levels of stability (eight and two), for any of the instability indices (general, anteroposterior and mediolateral). CONCLUSION: The lower-limb dominance did not influence single-foot balance among sedentary males.

scholarly journals Muscle Coactivation Before and After the Impact Phase of Running Following Isokinetic Fatigue

2011 ◽  
Vol 46 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Eleftherios Kellis ◽  
Andreas Zafeiridis ◽  
Ioannis G. Amiridis
Keyword(s):  
Muscle Activation ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Knee Extensors ◽  
Training Experience ◽  
Cross Sectional ◽  
Muscle Activation Patterns ◽  
Strength Capacity ◽  
Before And After ◽  
The Impact

Abstract Context: The effects of fatigue on impact loading during running are unclear, with some authors reporting increased impact forces and others reporting decreased forces. Objective: To examine the effects of isokinetic fatigue on muscle cocontraction ratios about the knee and ankle during running. Design: Cross-sectional study. Setting: Neuromechanics laboratory. Patients or Other Participants: Female middle-distance runners (age  =  21.3 ± 1.93 years) with at least 5 years of training experience. Intervention(s): Participants ran on the treadmill at 3.61 m/s before and immediately after the fatigue protocol, which consisted of consecutive, concentric knee extension-flexion at 120°/s until they could no longer produce 30% of the maximum knee-extension moment achieved in the familiarization session for 3 consecutive repetitions. Main Outcome Measure(s): Electromyographic (EMG) amplitude of the vastus medialis (VM), biceps femoris (BF), gastrocnemius (GAS), and tibialis anterior (TA) was recorded using surface electrodes. Agonist∶antagonist EMG ratios for the knee (VM∶BF) and ankle (GAS∶TA) were calculated for the preactivation (PR), initial loading response (LR1), and late loading response (LR2) phases of running. Hip-, knee-, and ankle-joint angular displacements at initial foot contact were obtained from 3-dimensional kinematic tracings. Results: Fatigue did not alter the VM∶BF EMG ratio during the PR phase (P &gt; .05), but it increased the ratio during the LR1 phase (P &lt; .05). The GAS∶TA EMG ratio increased during the LR1 phase after fatigue (P &lt; .05) but remained unchanged during the PR and LR2 phrases (P &gt; .05). Conclusions: The increased agonist EMG activation, coupled with reduced antagonist EMG activation after impact, indicates that the acute decrease in muscle strength capacity of the knee extensors and flexors results in altered muscle-activation patterns about the knee and ankle before and after foot impact.

A cross-sectional study of muscle strength and mass in 45- to 78-yr-old men and women

1991 ◽  
Vol 71 (2) ◽  
pp. 644-650 ◽  
Author(s):  
W. R. Frontera ◽  
V. A. Hughes ◽  
K. J. Lutz ◽  
W. J. Evans
Keyword(s):  
Muscle Strength ◽  
Peak Torque ◽  
Cross Sectional Study ◽  
Fat Free Mass ◽  
Knee Extensors ◽  
Cross Sectional ◽  
Men And Women ◽  
Age Related ◽  
Muscle Groups ◽  
Old Men

The isokinetic strength of the elbow and knee extensors and flexors was measured in 200 healthy 45- to 78-yr-old men and women to examine the relationship between muscle strength, age, and body composition. Peak torque was measured at 60 and 240 degrees/s in the knee and at 60 and 180 degrees/s in the elbow by use of a Cybex II isokinetic dynamometer. Fat-free mass (FFM) was estimated by hydrostatic weighing in all subjects, and muscle mass (MM) was determined in 141 subjects from urinary creatinine excretion. FFM and MM were significantly lower (P less than 0.001) in the oldest group. Strength of all muscle groups at both testing speeds was significantly (P less than 0.006) lower (range 15.5–26.7%) in the 65- to 78- than in the 45- to 54-yr-old men and women. When strength was adjusted for FFM or MM, the age-related differences were not significant in all muscle groups except the knee extensors tested at 240 degrees/s. Absolute strength of the women ranged from 42.2 to 62.8% that of men. When strength was expressed per kilogram of MM, these gender differences were smaller and/or not present. These data suggest that MM is a major determinant of the age- and gender-related differences in skeletal muscle strength. Furthermore, this finding is, to a large extent, independent of muscle location (upper vs. lower extremities) and function (extension vs. flexion).

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