Adaptations in skeletal muscle following strength training

1979 ◽  
Vol 46 (1) ◽  
pp. 96-99 ◽  
Author(s):  
D. L. Costill ◽  
E. F. Coyle ◽  
W. F. Fink ◽  
G. R. Lesmes ◽  
F. A. Witzmann
Keyword(s):  
Strength Training ◽  
Exercise Program ◽  
Knee Extensor ◽  
Peak Torque ◽  
Knee Extension ◽  
Type I ◽  
Muscle Area ◽  
Muscle Enzymes ◽  
Muscle Enzyme ◽  
Before And After

Five men were studied before and after 7 wk of isokinetic strength training to determine its effects on muscle enzyme activities and fiber composition. One of the subject's legs was trained using 10 repeated 6-s maximal work bouts, while the other leg performed repeated 30-s maximal knee extension exercise. The total work accomplished by each leg was constant. Training 4 times/wk achieved similar gains in peak torque for both legs at the training velocity (3.14 rad/s) and at slower speeds. Fatigability of the knee extensor muscles, as measured by a 60-s exercise test, was similar in both legs after training. Biopsy specimens showed significant changes in the % of the muscle area composed of type I and IIa fibers as a result of both strength training programs. In terms of muscle enzymes, only the 30 s exercise program resulted in elevated glycolytic, ATP-CP and mitochondrial activities. Despite these changes, none of the parameters measured were found to be related to the gains in either muscle strength or fatigability during maximal isokinetic contractions.

scholarly journals The Effect of Applying Rigid Taping to Quadriceps Muscles on Knee Extension Strength and Jumping Distance

2014 ◽  
Vol 2 (11_suppl3) ◽  
pp. 2325967114S0017
Author(s):  
Burak Yasin Yasar ◽  
Tuba Kaplan ◽  
Sabriye Ercan ◽  
Erkan Alp ◽  
Cem Cetin
Keyword(s):  
Lower Limb ◽  
Performance Enhancement ◽  
Knee Extensor ◽  
Peak Torque ◽  
Knee Extension ◽  
Knee Extension Strength ◽  
Jump Distance ◽  
Before And After ◽  
Isokinetic Torque ◽  
Work Done

Objectives: The scientific literature is insufficient to support the use of elastic or rigid taping for the prevention or treatment of musculoskeletal injury or performance enhancement. The aim of this study was to analyze the effects of applying rigid taping on the knee extension strength and lower limb function in healthy subjects. Methods: Twenty eight healthy volunteers (age: 20.9 ± 1.1 years) were randomly assigned to two groups of 14 subjects each: Placebo/sham tape and rigid tape (Rigid tape application over the same muscles). All individuals were assessed for single and double leg hops and peak isometric and concentric isokinetic torque before and after interventions. Results: There were no statistically significant differences in jumping distances, isometric peak torque, isokinetic peak torque and total work done between groups. Conclusion: Application of rigid tape to quadriceps muscles did not significantly change lower limb functions, jump distance and knee extensor peak torque in healthy sedentary subjects.

scholarly journals Knee Muscles Isokinetic Evaluation after a Six-Month Regular Combined Swim and Dry-Land Strength Training Period in Adolescent Competitive Swimmers

2015 ◽  
Vol 49 (1) ◽  
pp. 195-200 ◽  
Author(s):  
Athanasios A. Dalamitros ◽  
Vasiliki Manou ◽  
Kosmas Christoulas ◽  
Spiros Kellis
Keyword(s):  
Strength Training ◽  
Knee Extensor ◽  
Peak Torque ◽  
Knee Extension ◽  
Training Period ◽  
Similar Data ◽  
Dry Land ◽  
Isokinetic Testing ◽  
Torque Values ◽  
Competitive Swimmers

Abstract Previous studies demonstrated significant increases in the shoulder internal rotators’ peak torque values and unilateral muscular imbalances of the shoulder rotators after a competitive swim period. However, there are no similar data concerning the knee muscles. The purpose of the current study was to examine the effects of a six-month training period on knee flexor and extensor peak torque values, examine a possible bilateral strength deficit and evaluate the unilateral strength balance in competitive swimmers. Eleven male adolescent swimmers (age: 14.82 ± 0.45 years) were tested for concentric knee extension and flexion peak torque (60°/s) with an isokinetic dynamometer, before and after a regular combined swim and dry-land strength training period. A trend towards greater improvements in the knee extensor compared to flexor muscles peak torque was observed. Furthermore, the bilateral strength deficit remained almost unchanged, whereas unilateral strength imbalance was increased for both limbs. However, all results were nonsignificant (p > 0.05). According to the data presented, a six-month regular combined swim and dry-land strength training period caused non-significant alterations for all the parameters evaluated during isokinetic testing. This study highlights the fact that competitive adolescent swimmers demonstrated unilateral knee strength imbalances throughout a long period of their yearly training macrocycle.

scholarly journals Can Strength Training Predictably Improve Gait Kinematics? A Pilot Study on the Effects of Hip and Knee Extensor Strengthening on Lower-Extremity Alignment in Cerebral Palsy

2010 ◽  
Vol 90 (2) ◽  
pp. 269-279 ◽  
Author(s):  
Diane L. Damiano ◽  
Allison S. Arnold ◽  
Katherine M. Steele ◽  
Scott L. Delp
Keyword(s):  
Cerebral Palsy ◽  
Strength Training ◽  
Computer Simulations ◽  
Exercise Program ◽  
Knee Extensor ◽  
Isokinetic Testing ◽  
Before And After ◽  
Generating Capacity ◽  
Muscle Groups ◽  
Analytical Approaches

Background Computer simulations have demonstrated that excessive hip and knee flexion during gait, as frequently seen in ambulatory children with cerebral palsy (CP), can reduce the ability of muscles to provide antigravity support and increase the tendency of hip muscles to internally rotate the thigh. These findings suggest that therapies for improving upright posture during gait also may reduce excessive internal rotation. Objective The goal of this study was to determine whether strength training can diminish the degree of crouched, internally rotated gait in children with spastic diplegic CP. Design This was a pilot prospective clinical trial. Methods Eight children with CP participated in an 8-week progressive resistance exercise program, with 3-dimensional gait analysis and isokinetic testing performed before and after the program. Secondary measures included passive range of motion, the Ashworth Scale, and the PedsQL CP Module. To identify factors that may have influenced outcome, individual and subgroup data were examined for patterns of change within and across variables. Results Strength (force-generating capacity) increased significantly in the left hip extensors, with smaller, nonsignificant mean increases in the other 3 extensor muscle groups, yet kinematic and functional outcomes were inconsistent. The first reported subject-specific computer simulations of crouch gait were created for one child who showed substantial benefit to examine the factors that may have contributed to this outcome. Limitations The sample was small, with wide variability in outcomes. Conclusions Strength training may improve walking function and alignment in some patients for whom weakness is a major contributor to their gait deficits. However, in other patients, it may produce no change or even undesired outcomes. Given the variability of outcomes in this and other strengthening studies in CP, analytical approaches to determine the sources of variability are needed to better identify those individuals who are most likely to benefit from strengthening.

scholarly journals Musculoskeletal Outcomes from Chronic High-Speed, High-Impulse Resistance Exercise

2018 ◽  
Vol 39 (10) ◽  
pp. 791-801 ◽  
Author(s):  
John Caruso ◽  
Michael Voor ◽  
Jason Jaggers ◽  
T. Symons ◽  
Jeremy Stith ◽  
...  
Keyword(s):  
Mechanical Loading ◽  
High Speed ◽  
Type I Collagen ◽  
Training Session ◽  
Knee Extension ◽  
Type I ◽  
Before And After ◽  
Force Peak ◽  
Blood Marker ◽  
Hip Extension

AbstractWhile bones and muscles adapt to mechanical loading, it appears that very specific types of stimuli must be applied to achieve osteogenesis. Our study assessed musculoskeletal outcomes to 30 training sessions on an Inertial Exercise Trainer (Newnan, GA). Subjects (n=13) performed workouts with their left leg, while their right served as an untreated control. Workouts entailed three 60-s sets each of knee extension, hip extension and calf press exercises, separated by 90-s rests. Before and after the 30 training sessions, subjects underwent strength tests (knee and ankle extensors of both legs), DEXA scans (hip, knee and ankles of both legs), and blood draws. After 30 training sessions 2×2 ANOVAs showed left leg peak torques rose significantly. 2×2 ANCOVAs, with bone scan area as a covariate, showed significant left leg calcaneal bone mineral content (+29%) and density (+33%) increases after 30 training sessions. A significant decline in C-terminal telopeptides of type I collagen, a blood marker of bone resorption, also occurred after 30 training sessions. The Inertial Exercise Trainer’s large volume of training session repetitions elicited high peak force, peak acceleration and impulses that likely provided a mechanical loading stimulus that evoked calcaneal accretion.

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.

Can Hip Joint Position affect Quadriceps Muscle Responses during Knee Extension Exercise?

2020 ◽  
Vol 41 (13) ◽  
pp. 929-935
Author(s):  
Denis César Leite Vieira ◽  
Marco Aurélio Araujo Dourado ◽  
Lucas Ugliara ◽  
Joao Luiz Quagliotti Durigan ◽  
Brad J. Schoenfeld ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Muscle Thickness ◽  
Rectus Femoris ◽  
Peak Torque ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Knee Extensors ◽  
Work Output ◽  
Before And After ◽  
Knee Extension Exercise

AbstractThis study investigated the acute effects of seated and supine knee extension exercise on muscle swelling, torque, and work output. Twelve resistance-trained men performed two isokinetic concentric-only knee-extension training protocols at different hip positions in a counter-balanced order. They completed the knee extension exercise in the seated (hip angle at 85°) and supine (hip angle at 180°) positions. The torque and work output were assessed during each set. Moreover, muscle thickness of the middle and proximal vastus lateralis and rectus femoris were evaluated before and after each protocol and used as an indicator of muscle swelling. Middle rectus femoris and proximal vastus lateralis thickness increased significantly (p=0.01) with no difference between exercise variations. However, the middle vastus lateralis thickness increased (p=0.01) only after the seated knee extension exercise (~7%). Knee extensors’ peak torque and work output were approximately 8% higher (p=0.04) in the seated when compared to the supine hip position. There was a similar decrease in torque and work output throughout both protocols (p=0.98). In conclusion, seated knee extension exercises produced greater torque, work output, and muscle swelling in the vastus lateralis when compared to the supine knee extension exercise.

scholarly journals Proprioceptive Neuromuscular Facilitation Improves Balance and Knee Extensors Strength of Older Fallers

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Marcelo Pinto Pereira ◽  
Mauro Gonçalves
Keyword(s):  
Exercise Program ◽  
Knee Extensor ◽  
Training Group ◽  
Knee Extension ◽  
Knee Extensors ◽  
Control Group ◽  
Extension Rate ◽  
Neuromuscular Activation ◽  
Activation Level ◽  
Proprioceptive Neuromuscular Facilitation

Falls are one of the major problems for elderly people and proprioceptive exercises have been suggested as an alternative in rehabilitation and preventive programs. The purpose of this study was to investigate the influence of a proprioceptive neuromuscular facilitation (PNF) exercise program on balance, knee extension and flexion isometric torque, and knee extension rate of force development (RFD). Fourteen older faller subjects (>60 years) were equally assigned into two groups: a control group (CG: n=7) and a training group (TG: n=7). The PNF training program was performed for 10 weeks on TG, with a frequency of three times per week. Patients were assessed before and after the PNF program, with respect to balance (Berg Balance Scale score—BBS), knee maximal isometric extension and flexion torque, knee extensor RFD, and knee extensors and flexors neuromuscular activation level and coactivation level around the knee. After 10 weeks, balance (P<0.001) and knee extension torque (P=0.05) were improved in TG while no differences were found for CG. These improvements were mainly attributed to central nervous system adaptations, since no differences were found for neuromuscular activation level and coactivation.

Strength training the free limb attenuates strength loss during unilateral immobilization

2009 ◽  
Vol 106 (3) ◽  
pp. 830-836 ◽  
Author(s):  
Jonathan P. Farthing ◽  
Joel R. Krentz ◽  
Charlene R. A. Magnus
Keyword(s):  
Strength Training ◽  
Muscle Activation ◽  
Muscle Thickness ◽  
Strength Loss ◽  
Peak Torque ◽  
Ulnar Deviation ◽  
Before And After ◽  
Cross Education ◽  
The Right ◽  
Arm Strength

The objective was to determine if strength training the free limb during a 3-wk period of unilateral immobilization attenuates strength loss in the immobilized limb through cross-education. Thirty right-handed participants were assigned to three groups. One group ( n = 10) wore a cast and trained the free arm (Cast-Train). A second group ( n = 10) wore a cast and did not train (Cast). A third group ( n = 10) received no treatment (control). Casts were applied to the nondominant (left) wrist and hand by a physician. Strength training was maximal isometric ulnar deviation (right hand) 5 days/wk. Peak torque (dynamometer), electromyography (EMG), and muscle thickness (ultrasound) were assessed in both arms before and after the intervention. Cast-Train improved right arm strength [14.3 (SD 5.0) to 17.7 (SD 4.8) N·m; P < 0.05] with no significant muscle hypertrophy [3.73 (SD 0.43) to 3.84 (SD 0.52) cm; P = 0.09]. The immobilized arm of Cast-Train did not change in strength [13.9 (SD 4.3) to 14.2 (SD 4.6) N·m] or muscle thickness [3.61 (SD 0.51) to 3.57 (SD 0.43) cm]. The immobilized arm of Cast decreased in strength [12.2 (SD 3.8) to 10.4 (SD 2.5) N·m; P < 0.05] and muscle thickness [3.47 (SD 0.59) to 3.32 (SD 0.55) cm; P < 0.05]. Control showed no changes in the right arm [strength: 15.3 (SD 6.1) to 14.3 (SD 5.8) N·m; muscle thickness: 3.57 (SD 0.68) to 3.52 (SD 0.75) cm] or left arm [strength: 14.5 (SD 5.3) to 13.7 (SD 6.1) N·m; muscle thickness: 3.55 (SD 0.77) to 3.51 (SD 0.70) cm]. Agonist muscle activation remained unchanged after the intervention for both arms [right: 302 (SD 188) to 314 (SD 176) μV; left: 261 (SD 139) to 288 (SD 151) μV] with no group differences. Strength training of the free limb attenuated strength loss in the immobilized limb during unilateral immobilization. Strength training may have prevented muscle atrophy in the immobilized limb.

scholarly journals Musculoskeletal Outcomes from Chronic High-Speed High-Impact Resistive Exercise

2019 ◽  
Vol 7 (1) ◽  
pp. 22-32 ◽  
Author(s):  
L. Chen ◽  
E.A. Selimovic ◽  
M. Daunis ◽  
T.A. Bayers T ◽  
L.J. Vargas ◽  
...  
Keyword(s):  
Repeated Measures ◽  
High Speed ◽  
Time Course ◽  
Exercise Intervention ◽  
Knee Extensor ◽  
Peak Torque ◽  
Resistive Exercise ◽  
Before And After ◽  
Independent Variable ◽  
Over Time

AbstractSubjects (n=13) did 30 workouts with their left leg on an Inertial Exercise Trainer (IET), while their right leg served as an untreated control. Before and after the 30 workouts, they underwent isokinetic strength tests (knee and ankle extensors of both legs) whose peak torque (PT), time to PT (TTPT), and rate of torque development (RTD) values were each analyzed with 2(leg)×2(time)×3(velocity) analysis of variances (ANOVAs), with repeated measures per independent variable. Peak force (PF) and total work (TW) data were measured from each IET workout, and they represent time course strength changes produced by our exercise intervention. PF and TW values for the three IET exercises that comprised each workout were each analyzed with one-way ANOVAs with time as the independent variable. Results included significant ankle and knee extensor PT increases, whereby the left leg achieved higher values at posttesting, but there were no significant TTPT changes and a time effect for ankle extensor RTD. Our data show that PF and TW each had significant increases over time, with the latter exhibiting greater gains over the 30-workout intervention. Our results imply that the IET yields strength gains over time comparable to standard resistive exercise hardware.

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