Relationship Between Speed of Performing Leg Extension With 30 RM Load and the Selected EMG Variables of Selected Quadricep Muscles

The aim of the study was to assess the effects of speed of leg extension exercise with 30 RM load on the EMG activity of Vastus Medialis (VM) and Vastus Lateralis (VL). Seventeen healthy male subjects performed 30 repetition of leg extension exercise with 30 RM load in minimum time possible and EMG activity from VM and VL of right lower extremity was recorded simultaneously. Two new criteria, namely gross load speed of movement (GLSM) and relative load speed of movement (RLSM) were developed as the variables of speed of exercise. Selected variables of EMG activity were median frequency (MDF), mean frequency (MNF), root mean square (RMS), and integrated EMG (IEMG). Product moment and rank order correlation were calculated between the selected variables of EMG activity and selected variables of speed of exercise. The selected EMG variables, namely MDF and MNF, reported a negative significant relationship (p<0.05) with selected variables of speed of exercise whereas a selected EMG variables, namely RMS reported a positive significant relationship (p<0.05) with selected with the selected variables of speed of exercise.

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Effects of methylprednisolone on exercise-induced increases of plasma levels of polymorphonuclear elastase and myeloperoxidase in man. Preliminary results

Mediators of Inflammation ◽

10.1155/s0962935193000456 ◽

1993 ◽

Vol 2 (4) ◽

pp. 323-326 ◽

Cited By ~ 3

Author(s):

G. Camus ◽

J. Pincemail ◽

G. Deby-Dupont ◽

C. Deby ◽

A. Juchmès-Ferir ◽

...

Keyword(s):

Single Dose ◽

Oral Dose ◽

Significant Relationship ◽

Plasma Levels ◽

Oral Absorption ◽

Polymorphonuclear Neutrophil ◽

Healthy Male ◽

Experimental Conditions ◽

Exercise Induced ◽

Male Subjects

The aim of the present study was to verify whether a single oral dose of methylprednisolone could modulate the exercise-induced release of polymorphonuclear neutrophil (PMN) elastase and myeloperoxidase. Four healthy, male subjects were submitted to a 20 min downhill run (−20%) at 60% VO2max, 3 h after oral absorption of a placebo or a single dose of 32 mg methylprednisolone. A marked neutrophilia (+103% of basal PMN count; p < 0.02) was observed 3 h after methylprednisolone ingestion. During both exercise trials, placebo and methylprednisolone, PMN counts were increased by 46% and 19% (p < 0.05), respectively. The running test caused marked and significant (p < 0.05) increases in plasma myeloperoxidase concentration (MPO). The magnitude of MPO changes was the same in the two trials (+110%). Exercise also resulted in significant changes in plasma elastase concentration (EL) in both experimental conditions (placebo: +104%, p < 0.05; methylprednisolone: +338%, p < 0.005). Plasma elastase levels reached at the end of exercise on methylprednisolone were significantly higher than after placebo (p < 0.05). A significant relationship was found between EL and PMN in methylprednisolone trial only (r = 0.72; l0 < 0.005). These results showed that the transient exercise-induced release of elastase and myeloperoxidase were not decreased by methylprednisolone.

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Trunk Muscle Activity Increases With Unstable Squat Movements

Canadian Journal of Applied Physiology ◽

10.1139/h05-103 ◽

2005 ◽

Vol 30 (1) ◽

pp. 33-45 ◽

Cited By ~ 124

Author(s):

Kenneth Anderson ◽

David G. Behm

Keyword(s):

Vastus Lateralis ◽

Spinal Column ◽

Biceps Femoris ◽

Erector Spinae ◽

Trunk Muscles ◽

Emg Activity ◽

Key Words Electromyography ◽

Concentric Contractions ◽

Resistance Stability ◽

Male Subjects

The objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p < 0.05). Increased EMG activity of these muscles may be attributed to their postural and stabilization role. Furthermore, EMG activity was higher during concentric contractions compared to eccentric contractions. Performing squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL). Key words: electromyography, concentric, eccentric, resistance training, stabilizers

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Lower-Extremity Muscle Activation during the Star Excursion Balance Tests

Journal of Sport Rehabilitation ◽

10.1123/jsr.10.2.93 ◽

2001 ◽

Vol 10 (2) ◽

pp. 93-104 ◽

Cited By ~ 93

Author(s):

Jennifer Erin Earl ◽

Jay Hertel

Keyword(s):

Lower Extremity ◽

Repeated Measures ◽

Muscle Activation ◽

Vastus Lateralis ◽

Biceps Femoris ◽

Emg Activity ◽

Muscle Activation Patterns ◽

Lower Extremity Muscle ◽

Balance Tests ◽

Integrated Emg

Objective:To identify integrated EMG (I-EMG) activity of 6 lower-extremity muscles during the 8 Star Excursion Balance Tests (SEBTs).Design and Setting:Repeated measures, laboratory setting.Subjects:10 healthy young adults.Interventions:The SEBTs require the subject to balance on the stance leg and maximally reach with the contralateral foot along each of 8 lines extending from a common axis at 45° intervals.Measures:I-EMG activity of the vastus medialis obliquus (VMO), vastus lateralis (VL), medial hamstring (MH), biceps femoris (BF), anterior tibialis (AT), and gas-trocnemius.Results:Significant differences were found in all muscles (P < .05) except the gastrocnemius (P = .08). VMO and VL activity tended to be greatest with anteriorly directed excursions, whereas the MH and BF activity were greatest with posteriorly directed excursions. AT activity was lowest with the lateral excursion.Conclusions:Performance of the different SEBTs results in different lower-extremity muscle-activation patterns.

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Stretch-Shortening Cycle in Roller Ski Skating: Effects of Speed

Journal of Applied Biomechanics ◽

10.1123/jab.16.3.264 ◽

2000 ◽

Vol 16 (3) ◽

pp. 264-275 ◽

Cited By ~ 1

Author(s):

Stéphane Perrey ◽

Guillaume Millet ◽

Robin Candau ◽

Jean-Denis Rouillon

Keyword(s):

Cycle Length ◽

Vastus Lateralis ◽

Emg Activity ◽

Force Transmission ◽

Maximal Speed ◽

Integrated Emg ◽

Coupling Time ◽

Stretch Shortening Cycle ◽

Cross Country ◽

Gastrocnemius Lateralis

The purpose of this study was to examine the effects of speed on the stretch-shortening cycle (SSC) behavior during roller ski skating. Ten highly skilled male cross-country skiers roller skied at 4.56, 5.33 m · s–1and maximal speed using the V2-alternate technique on a flat terrain. Knee and ankle joint kinematics, and EMG of thevastus lateralis(VL) andgastrocnemius lateralis(GL) muscles were recorded during the last 40 s of each bout of roller skiing. Maximal speed was associated with increases in cycle rate combined with decreases in cycle length. For VL, no significant differences were observed for the integrated EMG eccentric-to-concentric ratio (iEMG Ecc/Conc) and for the stretching velocity over the range of speeds. For GL, stretching velocity and iEMG Ecc/Conc were significantly greater at maximal speed. The analysis of GL EMG activity suggests that speed improved GL stiffness so that more elastic energy was stored, a better force transmission occurred, and coupling time decreased. These findings suggest that the efficiency of roller ski skating locomotion may be increased with speed through a better use of the stretch-shortening cycle pattern in the ankle extensors.

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