scholarly journals Evidence of homologous and heterologous effects after unilateral leg training in youth

2018 ◽  
Vol 43 (3) ◽  
pp. 282-291 ◽  
Author(s):  
Aymen Ben Othman ◽  
David G. Behm ◽  
Anis Chaouachi
Keyword(s):  
Handgrip Strength ◽  
High Load ◽  
Upper Body ◽  
Knee Extensors ◽  
Leg Press ◽  
Positive Effects ◽  
Low Load ◽  
Cross Education ◽  
Education Effects ◽  
Unilateral Training

The positive effects of unilateral training on contralateral muscles (cross education) has been demonstrated with adults for over a century. There is limited evidence for cross education of heterologous muscles. Cross education has not been demonstrated with children. It was the objective of this study to investigate cross-education training in children examining ipsilateral and contralateral homologous and heterologous muscles. Forty-eight male children (aged 10–13 years) were assessed for unilateral, ipsilateral and contralateral lower limb strength, power and endurance (1-repetition maximum (RM) leg press, knee extensors (KE) and flexors (KF) maximum voluntary isometric contractions (MVIC), countermovement jump, muscle endurance test (leg press repetitions with 60% 1RM)), and upper body unilateral MVIC elbow flexors (EF) and handgrip strength. An 8-week training program involved 2 unilateral leg press resistance-training groups (high load/low repetitions: 4–8 sets of 5RM, and low load/high repetitions: 1–2 sets of 20RM) and control (untrained) group. All muscles exhibited improvements of 6.1% to 89.1%. The trained limb exhibited greater adaptations than the untrained limb for leg press 1RM (40.3% vs. 25.2%; p = 0.005), and 60% 1RM leg press (104.1% vs. 73.4%; p = 0.0001). The high load/low repetition training induced (p < 0.0001) greater improvements than low load/high repetition with KE, KF, EF MVIC and leg press 1RM. This is the first study to demonstrate cross-education effects with children and that the effects of unilateral training involve both contralateral homologous and heterologous muscles with the greatest strength-training responses from high-load/low-repetition training.

Effects of Low-Load Resistance Training with Vascular Occlusion on the Mechanical Properties of Muscle and Tendon

2006 ◽  
Vol 22 (2) ◽  
pp. 112-119 ◽  
Author(s):  
Keitaro Kubo ◽  
Teruaki Komuro ◽  
Noriko Ishiguro ◽  
Naoya Tsunoda ◽  
Yoshiaki Sato ◽  
...  
Keyword(s):  
Resistance Training ◽  
Vascular Occlusion ◽  
Load Resistance ◽  
Knee Extension ◽  
High Load ◽  
Muscle Volume ◽  
Knee Extensors ◽  
Specific Tension ◽  
Isometric Knee Extension ◽  
Low Load

The present study aimed to investigate the effects of low-load resistance training with vascular occlusion on the specific tension and tendon properties by comparing with those of high-load training. Nine participants completed 12 weeks (3 days/week) of a unilateral isotonic training program on knee extensors. One leg was trained using low load (20% of 1 RM) with vascular occlusion (LLO) and other leg using high load (80% of 1 RM) without vascular occlusion (HL). Before and after training, maximal isometric knee extension torque (MVC) and muscle volume were measured. Specific tension of vastus lateralis muscle (VL) was calculated from MVC, muscle volume, and muscle architecture measurements. Stiffness of tendon-aponeurosis complex in VL was measured using ultrasonography during isometric knee extension. Both protocols significantly increased MVC and muscle volume of quadriceps femoris muscle. Specific tension of VL increased significantly 5.5% for HL, but not for LLO. The LLO protocol did not alter the stiffness of tendon-aponeurosis complex in knee extensors, while the HL protocol increased it significantly. The present study demonstrated that the specific tension and tendon properties were found to remain following low-load resistance training with vascular occlusion, whereas they increased significantly after high-load training.

scholarly journals Dominant and nondominant leg press training induce similar contralateral and ipsilateral limb training adaptations with children

2019 ◽  
Vol 44 (9) ◽  
pp. 973-984 ◽  
Author(s):  
Aymen Ben Othman ◽  
Anis Chaouachi ◽  
Mehdi Chaouachi ◽  
Issam Makhlouf ◽  
Jonathan P. Farthing ◽  
...  
Keyword(s):  
Training Group ◽  
Knee Extensors ◽  
Random Allocation ◽  
Balance Test ◽  
Maximum Voluntary Isometric Contraction ◽  
Leg Press ◽  
Training Adaptations ◽  
Cross Education ◽  
Post Test ◽  
Hop Test

Cross-education has been extensively investigated with adults. Adult studies report asymmetrical cross-education adaptations predominately after dominant limb training. The objective of the study was to examine unilateral leg press (LP) training of the dominant or nondominant leg on contralateral and ipsilateral strength and balance measures. Forty-two youth (10–13 years) were placed (random allocation) into a dominant (n = 15) or nondominant (n = 14) leg press training group or nontraining control (n = 13). Experimental groups trained 3 times per week for 8 weeks and were tested pre-/post-training for ipsilateral and contralateral 1-repetition maximum (RM) horizontal LP, maximum voluntary isometric contraction (MVIC) of knee extensors (KE) and flexors (KF), countermovement jump (CMJ), triple hop test (THT), MVIC strength of elbow flexors (EF) and handgrip, as well as the stork and Y balance tests. Both dominant and nondominant LP training significantly (p < 0.05) increased both ipsilateral and contralateral lower body strength (LP 1RM (dominant: 59.6%–81.8%; nondominant: 59.5%–96.3%), KE MVIC (dominant: 12.4%–18.3%; nondominant: 8.6%–18.6%), KF MVIC (dominant: 7.9%–22.3%; nondominant: nonsignificant–3.8%), and power (CMJ: dominant: 11.1%–18.1%; nondominant: 7.7%–16.6%)). The exception was that nondominant LP training demonstrated a nonsignificant change with the contralateral KF MVIC. Other significant improvements were with nondominant LP training on ipsilateral EF 1RM (6.2%) and THT (9.6%). There were no significant changes with EF and handgrip MVIC. The contralateral leg stork balance test was impaired following dominant LP training. KF MVIC exhibited the only significant relative post-training to pretraining (post-test/pre-test) ratio differences between dominant versus nondominant LP cross-education training effects. In conclusion, children exhibit symmetrical cross-education or global training adaptations with unilateral training of dominant or nondominant upper leg.

scholarly journals Neuromuscular electrical stimulation in early rehabilitation of patients with postoperative complications after cardiovascular surgery

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
P Oleinik ◽  
AN Sumin ◽  
AV Bezdenezhnykh
Keyword(s):  
Postoperative Complications ◽  
Cardiovascular Surgery ◽  
Handgrip Strength ◽  
Left Knee ◽  
Baseline Data ◽  
Knee Extensors ◽  
Federal State ◽  
Control Group ◽  
Initial Strength ◽  
Knee Flexors

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Federal State Budgetary Scientific Institution Research Institute for Complex Issues of Cardiovascular Diseases Introduction The purpose was to evaluate the effectiveness of NMES in patients with complications after cardiac surgery. Methods This study was 37 patients who had significant postoperative complications after cardiovascular surgery. Participants were randomly - NMES group, n = 18; control, n = 19. It was not possible to blind the investigator. Analyzed basic clinical data. The dynamometry of the muscles upper and lower extremities was carried out, as well as a 6-minute walk test (6MWT). Also, the thickness of the quadriceps was measured using ultrasound.The patients underwent NMES on the quadriceps femoris muscle, daily from the third postoperative day, until discharge. The duration session was 90 minutes. Outcomes No differences were found in the baseline characteristics of the groups, including the results of laboratory and instrumental studies. Groups were comparable in the surgery and perioperative parameteres. The initial strength indicators also had no significant differences in the groups. At discharge knee extensors strength (KES) was significantly higher in the NMES group. The knee flexor strength (KFS) and handgrip strength (HF) increased the same in both groups. The quadriceps crosssectional area (CSA) muscle increased more in the NEMS group than in the control to the time of discharge. Average KES increased to a greater extent in the NMES group. At the same time, average and maximum KFS increased equally in both groups. A 6MWT before discharge did not show a difference between groups (P=.166). The NMES course did not affect the duration of hospitalisation (P=.429). Discussion This pilot study show beneficial effects of NMES on muscle strength in patients with complications after cardiovascular surgery. Physical tests initially and in dynamics NEMS Group (n = 18) Control group (n = 19) Baseline Discharge Baseline Discharge P-level Right knee extensors strength (kg) 20,3 [17,9; 26,1] 28,05 [23,8; 36,2] * 20,1 [18,6; 25,4] 22,3 [20,1; 27,1] * 0,004 Left knee extensors strength (kg) 17,75 [15,5; 27,0] 27,45 [22,3; 33,1] * 20,8 [17,5; 24,2] 22,5 [20,1; 25,9] * 0,017 Right knee flexors strength (kg) 14,85 [11,7; 19,5] 17,5 [14,1; 23,4] * 16,9 [13,1; 23,8] 19,2 [12,5; 26,4] * 0,971 Left knee flexors strength (kg) 14,7 [12,6; 19,6] 19,75 [15,9; 24,2] * 16,2, [10,4; 25,1] 18,8 [13,1; 27,7] * 0,889 6-MWT (m) 148,5 [108,5; 174,0] 288,0 [242,0; 319,0] * 169,0 [115,0; 217,0] 315,0 [277,0; 400,0] * 0,166 Right handgrip strength (kg) 24,5 [15,0; 33,0] 25,5 [19,0; 36,0] * 27,0 [18,0; 32,0] 30,0 [20,0; 35,0] * 0,795 Left handgrip strength (kg) 17,0 [12,0; 27,0] 21,0 [15,0; 31,0] * 19,0 [14,0; 29,0] 23,0 [16,0; 30,0] * 0,541 * - p-level from baseline data &lt; 0,05 ** - p-level from baseline data ≥ 0,05

Study on bearing stiffness characteristics with residual stress in carburized layer

2020 ◽  
pp. 095440622096079
Author(s):  
Junshuai Liang ◽  
Ning Li ◽  
Jingyu Zhai ◽  
BaoGang Wen ◽  
Qingkai Han ◽  
...  
Keyword(s):  
Residual Stress ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
High Load ◽  
Axial Stiffness ◽  
Fe Model ◽  
Low Load ◽  
Bearing Stiffness ◽  
Carburized Layer ◽  
Stiffness Characteristics

In this study, a layering method of carburized ring is presented. A finite element (FE) model for analyzing bearing stiffness characteristics is established considering the residual stress in the carburized layer. The residual stress in the carburized layer of a double-row conical roller bearing is tested and the influence of the distribution of residual stress in carburized layer on the bearing stiffness is investigated. Results show that the residual stress in the carburized layer increases the contact stiffness of the bearing by 5% in the low-load zone and 3% in the high-load zone. The radial stiffness of the bearing is increased by 5% in the low-load zone and 3% in the high-load zone. The axial stiffness is increased by 6%, and the angular stiffness increased by 4%. The larger the thickness of the carburized layer, the greater the residual compressive stress in the carburized layer, the deeper the position of the maximum residual stresses in the carburized layer will lead to the greater stiffness of the bearing.

Effects of the use neuromuscular electrical stimulation of the lower extremities in the prehabilitation of patients in a before cardiac surgery

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
P Oleinik ◽  
AN Sumin ◽  
AV Bezdenezhnykh
Keyword(s):  
Cardiac Surgery ◽  
Handgrip Strength ◽  
Lower Extremities ◽  
Left Knee ◽  
Knee Extensors ◽  
Control Group ◽  
Elective Cardiac Surgery ◽  
Antagonist Muscles ◽  
Muscle Groups ◽  
Knee Flexors

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Research Institute for Complex Issues of Cardiovascular Diseases Aim To evaluate the effects of neuromuscular electrostimulation in the prehabilitation and prevention of muscle weakness in patients awaiting cardiac surgery. Materials and methods 122 patients waiting for elective cardiac surgery were included. Exclusion criteria: age less than 25 and more than 80 years; emergency and urgent surgical interventions; arthropathies; low pain threshold; rhabdomyolysis and other myopathies; cognitive dysfunction. Routine laboratory and instrumental examinations were performed in all patients upon admission to the hospital, as part of a standard examination. 62 patients were randomly selected for the preoperative NMES group, in addition to the standard preoperative preparation and treatment program. The standard program included 60 control patients. Patients of the NMES group underwent quadriceps stimulation for at least 5 sessions, lasting 90 minutes, daily before surgery. Results. The groups were comparable and did not have significant differences in gender and age characteristics, according to the main clinical and anamnestic data and types of operations. Initially, there were no differences in the state of the muscles of the lower extremities, the distance of the six-minute walking test (6MWT), and the strength of the hand grip. After NMES, there was an increase in muscle strength relative to the control group, both stimulated muscle groups and unstimulated antagonist muscles, as well as a greater 6MWT distance and hand compression force. All the differences were significant. Conclusions The course of pre-rehabilitation of NMES before surgery, allowed to maintain, and in some cases improve the condition of the muscle frame of the lower extremities. A positive effect was observed not only in stimulated muscle groups, but also in antagonist muscles Indicators of muscle status NMES (n = 62) Control group (n = 60) Baseline Discharge Baseline Discharge P-level Right knee extensors strength (kg) 24,4 [18,3; 31,4] 30,4 [23,8; 36,2]* 24,7 [20,1; 33,2] 22,25 [18,9; 30,4] &lt;0,001 Left knee extensors strength (kg) 23,8 [19,3; 31,3] 29,2 [23,6; 35,4]* 25,75 [19,2; 31,3] 22,9 [18,9; 27,8] &lt;0,001 Right knee flexors strength (kg) 18,9 [13,3; 24,0] 21,7 [16,6; 25,1] 19,55 [13,1; 26,0] 16,7 [12,1; 23,3] 0,006 Left knee flexors strength (kg) 19,3 [14,3; 24,5] 21,9 [17,3; 26,7] 19,5 [13,0; 24,3] 18,2 [13,4; 22,2] 0,005 6-MWT (m) 300,0 [261,0; 371,0] 331,0 [280,0; 375,0] 304,5 [253,0; 380,0] 285,5 [246,0; 342,0] 0,006 Right handgrip strength (kg) 28,5 [20,5; 34,0] 31,5 [22,0; 34,0] 29,0 [19,0; 34,0] 27,0 [19,0; 33,0] 0,054 Left handgrip strength (kg) 25,0 [18,0; 31,0] 25,0 [18,0; 32,0] 24,0 [15,0; 31,0] 22,0 [14,0; 28,0] 0,062 * - p-level from baseline data &lt; 0,05 Abstract Figure. dynamics of stimulated muscles

Low-load resistance training with low relative pressure produces muscular changes similar to high-load resistance training

2017 ◽  
Vol 56 (6) ◽  
pp. E126-E133 ◽  
Author(s):  
Daeyeol Kim ◽  
Jeremy P. Loenneke ◽  
Xin Ye ◽  
Debra A. Bemben ◽  
Travis W. Beck ◽  
...  
Keyword(s):  
Resistance Training ◽  
Load Resistance ◽  
High Load ◽  
Relative Pressure ◽  
Low Load

Blood Flow Restriction Therapy Impact on Musculoskeletal Strength and Mass

2021 ◽  
Vol 1 (5) ◽  
pp. 263502542110326
Author(s):  
Steven R. Dayton ◽  
Simon J. Padanilam ◽  
Tyler C. Sylvester ◽  
Michael J. Boctor ◽  
Vehniah K. Tjong
Keyword(s):  
Blood Flow ◽  
Resistance Training ◽  
Muscle Strength ◽  
Load Resistance ◽  
High Load ◽  
Blood Flow Restriction ◽  
Occlusion Pressure ◽  
Total Occlusion ◽  
Flow Restriction ◽  
Low Load

Background: Blood flow restriction (BFR) training restricts arterial inflow and venous outflow from the extremity and can produce gains in muscle strength at low loads. Low-load training reduces joint stress and decreases cardiovascular risk when compared with high-load training, thus making BFR an excellent option for many patients requiring rehabilitation. Indications: Blood flow restriction has shown clinical benefit in a variety of patient populations including healthy patients as well as those with osteoarthritis, anterior cruciate ligament reconstruction, polymyositis/dermatomyositis, and Achilles tendon rupture. Technique Description: This video demonstrates BFR training in 3 clinical areas: upper extremity resistance training, lower extremity resistance training, and low-intensity cycling. All applications of BFR first require determination of total occlusion pressure. Upper extremity training requires inflating the tourniquet to 50% of total occlusion pressure, while lower extremity exercises use 80% of total occlusion pressure. Low-load resistance training exercises follow a specific repetition scheme: 30 reps followed by a 30-second rest and then 3 sets of 15 reps with 30-seconds rest between each. During cycle training, 80% total occlusion pressure is used as the patient cycles for 15 minutes without rest. Results: Augmenting low-load resistance training with BFR increases muscle strength when compared with low-load resistance alone. In addition, low-load BFR has demonstrated an increase in muscle mass greater than low-load training alone and equivalent to high-load training absent BFR. A systematic review determined the safety of low-load training with BFR is comparable to traditional high-intensity resistance training. The most common adverse effects include exercise intolerance, discomfort, and dull pain which are also frequent in patients undergoing traditional resistance training. Severe adverse effects including deep vein thrombosis, pulmonary embolism, and rhabdomyolysis are exceedingly rare, less than 0.006% according to a national survey. Patients undergoing BFR rehabilitation experience less perceived exertion and demonstrate decreased pain scores compared with high-load resistance training. Conclusion: Blood flow restriction training is an effective alternative to high-load resistance training for patients requiring musculoskeletal rehabilitation for multiple disease processes as well as in the perioperative setting. Blood flow restriction has been shown to be a safe training modality when managed by properly trained physical therapists and athletic trainers.

Effect of stirring time on the mechanical behavior of friction stir spot weld of Al 6061-T6 lap-shear configuration

2018 ◽  
Vol 233 (10) ◽  
pp. 3583-3591 ◽  
Author(s):  
Amirreza Shahani ◽  
Ali Farrahi
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Static Strength ◽  
High Load ◽  
Welding Condition ◽  
Friction Stir ◽  
Al 6061 ◽  
Lap Shear ◽  
Low Load ◽  
Stirring Time

The effect of five different stirring times of friction stir spot welding on lap-shear specimens of Al 6061-T6 alloy has been experimentally analyzed. The welding condition with 2 s of stirring shows the optimum mechanical behavior in comparison to the others. The static strength and fatigue behavior of the joint are justified using the microhardness profiles. The static results prove that the increase of stirring time beyond the 2 s case has little effect on improving the static strength. The fatigue results reveal two different failure modes, which are shear fracture at high load levels and transverse crack growth at low load levels. At medium load levels, although the final failure is similar to high load levels, the transverse growth of the crack outside the welding zone, just like low load levels, is also observed.

Progression in den Methoden: von „Low Load“ zu „High Load“

Sportphysio ◽  
2020 ◽  
Vol 08 (01) ◽  
pp. 16-28
Author(s):  
Hans-Josef Haas ◽  
Christian Szepessy Steinmann
Keyword(s):  
High Load ◽  
Low Load

Bis ein Sportler nach einer Verletzung wieder am Wettkampf teilnehmen kann, müssen seine motorischen Fähigkeiten abhängig von den Heilungsvorgängen spezifisch entwickelt werden – ein komplexer Prozess, bei dem viele Aspekte berücksichtigt werden müssen.

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