Body Weight Load Research Articles

Correlation Between Bench Press and Pushup Repetitions to Failure Relative to Bodyweight

The bench press and pushup are popular exercises used to develop strength and power. They are also often associated with equal benefits in developing upper body muscular endurance. However, it is unknown how they are related as pushups use a bodyweight load while the bench press uses greater weight. PURPOSE: To investigate the correlation between bench press and pushup repetitions to failure relative to a bodyweight load. METHODS: Fourteen recreationally trained males (age=24.71±2.64yrs, height=177.29±6.87, mass=83.74±9.41) performed a 1RM bench press test and an isometric pushup to determine bodyweight load supported in both the up and down positions. Grip width on the bench press was measured as the distance between middle fingers and this distance was used for hand placement during pushups. Subjects were positioned for a pushup with their hands on an AMTI force plate and their feet off the plate. Isometric force was measured for 3 seconds in the up and down positions, in random order. For the down position, triceps were parallel to the floor, while for the up position, triceps were perpendicular to the floor. Days 2 and 3 consisted of performing repetitions to failure for either the bench press or pushup exercise. For the pushup, subjects performed repetitions following an 80/s tempo. The test was terminated if they failed to complete a full repetition, could not maintain cadence or there were three faults in form. For the bench press, subjects performed repetitions to failure with a load that was equal to the average relative bodyweight force of the up and down pushup positions. RESULTS: There was a very low relationship (r=0.289) between bench press repetitions to failure (29.5±7.59) and push up repetitions to failure (33.0±6.53). Load for the bench press test, relative to their 1RM (0.51%±0.07) was significantly less than the pushup down position (0.75%±0.03), up position (0.71%±0.03), and the average of the up and down positions (0.73%±0.03) relative to their body mass. CONCLUSIONS: The bench press and pushup must be seen as two distinct and different exercises that use very different loads, which could result in dissimilar upper body muscular endurance adaptations.

A Three Dimensional Finite Element Analysis of Mechanical Stresses in the Human Knee Joint: Problem of Cartilage Destruction

Knee malalignment is considered one of the key biomechanical factors that influence the progression of knee osteoarthritis. In this context, a three-dimensional Finite Element model of the knee joint is developed and used to investigate the effect of the frontal plane femoro-tibial angle as well as the body weight load on the stress distribution in the knee cartilage and menisci. Therefore, the knee joint model is obtained through CAD software. Bones, articular cartilage and menisci are considered linear, elastic and isotropic materials. Ligaments were modelled using connectors. Consequently, contact pressures and equivalent stress (von-Mises) are calculated in Abaqus software. This model was validated using experimental and numerical results obtained by other authors. Results of this work demonstrated that; compressive stress and contact pressure on the medial compartment of the knee joint were found to be larger compared to those in the lateral compartment when the femoro-tibial angle and the body weight load increased from 0° to 12° varus and 500 N to 1250 N, respectively, suggesting that these two parameters might be risk factors for developing medial compartment knee osteoarthritis.

Use of a custom-made limb-press model to assess intra- and extracapsular techniques for treating cranial cruciate ligament rupture in cats.

Objectives This study aimed to compare the under-and-over technique, a type of intracapsular treatment, and the standard fabella-tibial suture, a method for extracapsular treatment, in achieving immediate, postoperative stifle stability after cranial cruciate ligament (CrCL) rupture by using a feline, custom-made limb-press model. Methods Cadaveric feline hindlimb specimens (n = 14) were positioned in the limb press at predefined joint angles (stifle joint: 120°; hock joint: 120°), and vertical loads of 5%, 10%, 20% and 30% body weight were applied statically. Mediolateral radiographic views were obtained of the stifles under each load before and after CrCL transection, as well as after treatment with either of the two surgical techniques, and differences in distance between two predefined radiographic points for each radiograph were analysed. Results The general linear model showed a significant effect of load ( P <0.01) and technique ( P = 0.004) and a significant interaction between load and technique ( P = 0.006) regarding craniocaudal stifle stability. Distances between predefined tibial and femoral reference points were consistently higher in transected CrCLs than in intact stifles. All standard fabella-tibial suture-treated stifles (n = 7) were stable at all loads tested. Of the seven under-and-over technique-treated stifles, one was unstable at 20% body weight load and three at 30% body weight load. Conclusions and relevance Our model, which appropriately reproduced certain aspects of domestic shorthair cat stifle mechanics, indicated that a 40 lb monofilament nylon prosthesis, tightened at 20 N, produces more favourable biomechanical stabilisation of craniocaudal cruciate-related stifle instability than a 0.5 cm wide strip of fascia lata applied intracapsularly.

Carrying asymmetric loads during stair negotiation

Individuals often carry items in one hand instead of both hands during activities of daily living. The combined effects of carrying asymmetric loads and stair negotiation may create even higher demands on the low back and lower extremity. The purpose of this study was to investigate the effect of symmetric and asymmetric loading conditions on L5/S1 and lower extremity moments during stair negotiation. Twenty-two college students performed stair ascent and stair descent on a three-step staircase (step height 18.5cm, tread depth 29.5cm) at preferred pace under five load conditions: no load, 10% body weight (BW) unilateral load, 20% BW unilateral load, 10% BW bilateral load, and 20% BW bilateral load. Video cameras and force platforms were used to collect kinematic and kinetic data. Inverse dynamics was used to calculate frontal plane moments for the L5/S1 and lower extremity. A 20% BW unilateral load resulted in significantly higher peak L5/S1 lateral bending, hip abduction, and external knee varus moments than nearly all other loading conditions during stair ascent and stair descent. Therefore, we suggest potential benefits when carrying symmetrical loads as compared to an asymmetric load in order to decrease the frontal joint moments, particularly at 20% BW load.

Early satiety and postprandial fullness in gastroparesis correlate with gastroparesis severity, gastric emptying, and water load testing.

Early satiety (ES) and postprandial fullness (PPF) are often present in gastroparesis, but the importance of these symptoms in gastroparesis has not been well-described. The aims were: (i) Characterize ES and PPF in patients with gastroparesis. (ii) Assess relationships of ES and PPF with etiology of gastroparesis, quality of life, body weight, gastric emptying, and water load testing. Gastroparetic patients filled out questionnaires assessing symptoms (PAGI-SYM) and quality of life (PAGI-QOL, SF-36v2). Patients underwent gastric emptying scintigraphy and water load testing. 198 patients with gastroparesis (134 IG, 64 DG) were evaluated. Early satiety was severe or very severe in 50% of patients. Postprandial fullness was severe or very severe in 60% of patients. Severity scores for ES and PPF were similar between idiopathic and diabetic gastroparesis. Increasing severity of ES and PPF were associated with other gastroparesis symptoms including nausea/vomiting, satiety/early fullness, bloating, and upper abdominal pain and GERD subscores. Increasing severity of ES and PPF were associated with increasing gastroparesis severity, decreased BMI, decreased quality of life from PAGI-QOL and SF-36 physical health. Increasing severity of ES and PPF were associated with increasing gastric retention of a solid meal and decreased volume during water load test. Early satiety and PPF are commonly severe symptoms in both diabetic and idiopathic gastroparesis. Early satiety and PPF severity are associated with other gastroparesis symptom severities, body weight, quality of life, gastric emptying, and water load testing. Thus, ES and PPF are important symptoms characterizing gastroparesis. ClinicalTrials.gov number: NCT NCT01696747.

Effects of two neuromuscular training programs on running biomechanics with load carriage: a study protocol for a randomised controlled trial.

BackgroundIn recent years, athletes have ventured into ultra-endurance and adventure racing events, which tests their ability to race, navigate, and survive. These events often require race participants to carry some form of load, to bear equipment for navigation and survival purposes. Previous studies have reported specific alterations in biomechanics when running with load which potentially influence running performance and injury risk. We hypothesize that a biomechanically informed neuromuscular training program would optimize running mechanics during load carriage to a greater extent than a generic strength training program.MethodsThis will be a two group, parallel randomized controlled trial design, with single assessor blinding. Thirty healthy runners will be recruited to participate in a six weeks neuromuscular training program. Participants will be randomized into either a generic training group, or a biomechanically informed training group. Primary outcomes include self-determined running velocity with a 20 % body weight load, jump power, hopping leg stiffness, knee extensor and triceps-surae strength. Secondary outcomes include running kinetics and kinematics. Assessments will occur at baseline and post-training.DiscussionTo our knowledge, no training programs are available that specifically targets a runner’s ability to carry load while running. This will provide sport scientists and coaches with a foundation to base their exercise prescription on.Trial registrationANZCTR (ACTRN12616000023459) (14 Jan 2016)Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-016-1271-9) contains supplementary material, which is available to authorized users.

Effects of load carriage and footwear on lower extremity kinetics and kinematics during overground walking

Kinetic and kinematic responses during walking vary by footwear condition. Load carriage also influences gait patterns, but it is unclear how an external load influences barefoot walking. Twelve healthy adults (5 women, 7 men) with no known gait abnormalities participated in this study (age=23±3years, height=1.73±0.11m, and mass=70.90±12.67kg). Ground reaction forces and 3D motion were simultaneously collected during overground walking at 1.5ms−1 in four conditions: Barefoot Unloaded, Shod Unloaded, Barefoot Loaded, and Shod Loaded. Barefoot walking reduced knee and hip joint ranges of motion, as well as stride length, stance time, swing time, and double support time. Load carriage increased stance and double support times. The 15% body weight load increased GRFs ∼15%. Walking barefoot reduced peak anteroposterior GRFs but not peak vertical GRFs. Load carriage increased hip, knee, and ankle joint moments and powers, while walking barefoot increased knee and hip moments and powers. Thus, spatiotemporal and kinematic adjustments to walking barefoot decrease GRFs but increase knee and hip kinetic measures during overground walking. The ankle seems to be less affected by these footwear conditions. Regardless of footwear, loading requires larger GRFs, joint loads, and joint powers.

An Integrated Musculoskeletal-Finite-Element Model to Evaluate Effects of Load Carriage on the Tibia During Walking.

Prior studies have assessed the effects of load carriage on the tibia. Here, we expand on these studies and investigate the effects of load carriage on joint reaction forces (JRFs) and the resulting spatiotemporal stress/strain distributions in the tibia. Using full-body motion and ground reaction forces from a female subject, we computed joint and muscle forces during walking for four load carriage conditions. We applied these forces as physiological loading conditions in a finite-element (FE) analysis to compute strain and stress. We derived material properties from computed tomography (CT) images of a sex-, age-, and body mass index-matched subject using a mesh morphing and mapping algorithm, and used them within the FE model. Compared to walking with no load, the knee JRFs were the most sensitive to load carriage, increasing by as much as 26.2% when carrying a 30% of body weight (BW) load (ankle: 16.4% and hip: 19.0%). Moreover, our model revealed disproportionate increases in internal JRFs with increases in load carriage, suggesting a coordinated adjustment in the musculature functions in the lower extremity. FE results reflected the complex effects of spatially varying material properties distribution and muscular engagement on tibial biomechanics during walking. We observed high stresses on the anterior crest and the medial surface of the tibia at pushoff, whereas high cumulative stress during one walking cycle was more prominent in the medioposterior aspect of the tibia. Our findings reinforce the need to include: (1) physiologically accurate loading conditions when modeling healthy subjects undergoing short-term exercise training and (2) the duration of stress exposure when evaluating stress-fracture injury risk. As a fundamental step toward understanding the instantaneous effect of external loading, our study presents a means to assess the relationship between load carriage and bone biomechanics.

Creatine supplementation decreases plasma lipid peroxidation markers and enhances anaerobic performance in rats

Objective: The study was to investigate the effects of creatine (Cr) supplementation on oxidative stress markers and anaerobic performance in rats.Methods: Sixty-four rats (Wistar) were divided into two groups: C, anaerobic exercised group (n = 32) and Cr, anaerobic exercised group supplemented with creatine (n = 32). Cr supplementation consisted of the addition of 2% Cr monohydrate to the diet. After 28 days, the rats performed acute exercise (6 × 30 seconds of vertical jumps in the water with 30 seconds rest and 50% of total body weight load attached in the back). The animals were euthanized before (pre) and at 0, 2, and 6 hours (n = 8) after acute exercise.Results: Acute exercise induced an increase in plasma malondialdehyde (MDA) and advanced oxidation protein products (AOPP), as well as increased total lipid hydroperoxides and AOPP in gastrocnemius muscle. Cr supplementation inhibited the formation of MDA and lipid hydroperoxides in plasma. However, the antioxidant action of Cr was observed only against AOPP in gastrocnemius muscle. Cr supplementation also increased (P < 0.05) anaerobic performance compared to the C group.Conclusion: Cr supplementation is able to inhibit the increase in plasma lipid peroxidation markers induced by high-intensity and short-duration exercise in rats; equivalent actions, however, were not observed fully in muscle tissue.

Effect of Magnitude of Backpack Load and Duration of Carriage on Pulmonary Function Parameters among Urban Young Adults of West Bengal, India: An Ergonomic Study

Background: The college students (18-25 years) compelled to carry backpack load and are susceptible to physiological stress. Acceptable load limit is 10-15% of Body Weight (BW) among children and adolescents. Pulmonary function is an important physiological parameter which governs the cumulative stress on the body. The relationship between backpack carriage and pulmonary function parameters has not been explicitly studied among young adults. Objectives: The study aimed to investigate the changes in Forced Vital Capacity(FVC), Forced Expiratory Volume in one second (FEV1) and Tiffeneau index (FEV1%) with different duration of carriage at the level of 15% and 10% load of BW compared to no load condition. Methods: Pulmonary function tests were performed using Mini Spir (software Winspiro PRO) at 0-1 min, 10-11 min, 15-16 min of carriage among males (n=13) and females (n=19) with 15% load of BW; females (n=10) with 10% load of BW. Repeated measures ANOVA and paired two tailed student’s t test were performed. Results: Repeated measures ANOVA revealed, there was significant difference in FVC and FEV1 at different durations, when females carried both 15% and 10% load of BW. While carrying 15% load of BW at 0-1 min,10-11 min,15-16 min, females showed significant difference in FEV1 (p=0.004; p=0.0001; p=0.0001, respectively), FVC (p=0.031; p=0.003; p=0.0002, respectively) and FEV1% (p=0.026; p=0.010; p=0.047, respectively); males showed significant difference in FEV1 at 15-16 min (p=0.044) compared to no load. Females carrying 10% load of BW showed significant difference in FEV1 at 0-1 min (p=0.027) and 15-16 min (p=0.020), FVC in 15-16 min (p=0.024) compared to no load. Obstructive pattern was observed among females (n=10) with increased load. Conclusion: Males must not carry 15% static load of BW for more than 15 min and females should carry load lower than 10% of BW.

AQUATIC THERAPY IN BONE MINERAL DENSITY IN RATS AFTER PAW DISUSE BY IMMOBILIZATION

The locomotor system immobilization although used with therapeutic purpose often leads to muscle and bone changes. The use of aquatic therapy favors the body metabolism usually used as a functional recovery mechanism. The aim of this study was to assess the aquatic therapy on bone mineral density (BD) of post-immobilization paw in rats. It was used 20 Wistar female rats (± 20 weeks) divided into: control (C), Immobilization (I), Aquatic Therapy (AT) and Immobilization/Aquatic Therapy (IAT). The detention took place for two weeks involving the trunk and the right leg. The aquatic therapy occurred for three weeks, six sections per week starting with 2 minutes with addition of two minutes per day reaching 36 minutes on the last day with the increment of a 5% load of body weight. After the period of immobilization and rehabilitation, the animals were anesthetized (Ketamine /Xylazine) and sacrificed. For statistical analysis, it was used ANOVA with post hoc Bonferroni (p

Evaluation of bone mineral density and bone strength in autochthonous transgenic model mice for diabetes mellitus (Akita mice)

ObjectivesDiabetes mellitus (DM) causes secondary osteoporosis, which reduces bone mineral density (BMD) and bone strength. Akita mice (AM) are DM model mice used to evaluate glucose metabolism. However, bone metabolism in AM remains unclear. The purpose of this study was to evaluate BMD, bone strength, and serum sclerostin levels in AM. MethodsFemale AM and control mice (C57/BL/6NCrSlc; CM) were divided into four groups: (1) a CM group sacrificed at 14 (CM-14w; n = 8) or (2) 18 weeks of age (CM-18w; n = 6); and (3) an AM group sacrificed at 14 (AM-14w; n = 9) or (4) 18 weeks of age (AM-18w; n = 6). Blood glucose level, serum sclerostin level, total tibial BMD, and femoral shaft bone strength were evaluated at each time point. ResultsBlood glucose levels were significantly higher in AM than in CM (p < 0.001). Serum sclerostin levels were significantly lower in AM-18w than in CM-18w (p < 0.001). BMD was significantly lower in AM-14w than in CM-14w (p = 0.004). Stiffness of the femoral shaft was significantly lower in AM-18w than in CM-14w (p = 0.04). Body weight (r = 0.608, p < 0.01) and maximum load (r = 0.438, p < 0.05) were significantly positively correlated with serum sclerostin levels, while blood glucose levels showed a significant negative correlation (r = −0.708, p < 0.01). ConclusionsAM showed decreased BMD and bone strength with lower levels of serum sclerostin than CM.

Development of a piggyback-type transfer assist system to assist caregivers with patients being unable to move themselves

In this study, a transfer assist system for patients who are unable to move themselves was proposed for transferring them conveniently and comfortably among bed, wheelchair, and toilet bowl. The system that applies piggybacking as the transfer method was developed via kinematics that shows the interaction between humans and machines, biomechanical analysis, and Finite element analysis (FEA). To develop a system that uses a piggybacking method, a mobile-lift structure with an actuator module that supplies the least force required to have a piggybacking effect and to lift and support body-weight loads was designed by analyzing the characteristics of piggybacking persons. A mechanical design that can be worn rapidly (within 1 min) was applied, and an upper-body support cushion and thigh- and backattached pads with a structure that supports and distributes a body-weight load uniformly while piggybacking using the system were developed. Stresses between human bodies and the machine depending on the upper-body bending angle in the piggybacking motion were analyzed through FEA and biomechanical simulation, thereby determining the stable attachment position of the attachment pads that can distribute loads uniformly and give the least body pressure to humans. This study provided an experiment to verify the comfort and reliability of the system that applies piggybacking and to minimize the pain caused by the pressure of the device from a patient’s viewpoint. The system also reduces the physical burden of caregivers with the mechanical convenience. This convenience is achieved by providing a series of processes that allow transfer patients from bed to the system and to toilet bowl rapidly without difficulty for the caregivers.

One-sided hip-preserving and concurrent contralateral total hip arthroplasty for the treatment of bilateral osteonecrosis of the femoral head in different stages: short-medium term outcomes

BackgroundWe aimed to evaluate the clinical and radiological short-medium term outcomes for the treatment of bilateral osteonecrosis of the femoral head (ONFH) with hip-preserving surgery of core decompression followed by tightly impaction bone grafting combining with non-vascularized fibular allografting in one hip and concurrent one-stage total hip arthroplasty (THA) in the contralateral side. We hypothesized the aforementioned surgery showed benefits of protecting the preserved hip from collapsing and thereafter THA was delayed or avoided.MethodsWe retrospectively reviewed a consecutive series of 18 non-traumatic bilateral ONFH patients (36 hips) who had undergone previous mentioned surgeries between July 2004 and June 2013. Preoperative and the last follow-up Harris Hip Score (HHS) and Visual Analogue Scale (VAS) Score were obtained for clinical outcomes evaluation and X-rays of antero-posterior and frog-leg lateral views of bilateral hips were compared for radiological outcomes assessment.ResultsAll patients were telephone contacted for out-patient clinic return visit at an average follow-up time of 53.3 months (ranged from 20 months to 107 months). Of the 18 patients (15 men and 3 women), there were 5 patients were diagnosed preoperative IIB stages according to classification of the Association Research Circulation Osseuse classification (ARCO) and the remaining 13 patients were in ARCO IIIC stages. The mean age of the included patients was 40.7 years (range from 22 to 59 years). No age and followed-up time difference existed in genders. The postoperative HHS were 83.8 ± 17.9 points, and it revealed statistical significance when compared to preoperative 61.6 ± 17.0 points (p < 0.05). The VAS scores were reduced from preoperative 6.2 ± 2.0 points to postoperative 2.8 ± 2.3 points, which also manifested outcomes significance (p < 0.05). From radiological aspects, 14 patients acquired well repairmen of the necrotic areas of the femoral head. However, the other 4 patients ultimately suffered femoral head collapse, and the severe pain was gotten rid of after THA surgeries were performed.ConclusionsThe un-collapsed hip can achieve biological stability and sufficient blood supply through the hip-preserving surgery and obtain longtime repairmen of the necrotic bone as well as early non-weight-bearing function training, which benefits from distributing the whole body weight load to the hip of one-stage THA. Consequently, we recommend this sort of surgery for clinical practice trial when faced bilateral ONFH in different stages though longer time follow-up and larger samples are essentially needed to address its efficacy.

A Novel Weighted Suit to Assess Ambulatory Performance Under Reduced Strength-to-Body Weight Conditions

Performance outcomes of ambulatory tasks are influenced by human performance capabilities as they relate to one’s own body weight (e.g., strength to body weight). Alterations in this body-weight-specific performance are relevant to situations in which performance is impaired with minimal impact to body weight (e.g., muscle deconditioning in astronauts or aging), and also conditions where total weight to be carried is increased without a corresponding increase in performance (e.g., firefighters or soldiers who are required to carry heavy gear). PURPOSE: To use a novel weighted suit that has been specifically designed to manipulate strength to body weight (BW) ratios to determine the effects on extended duration (5 minutes to 2 hours) task performance. METHODS: Baseline aerobic capacity, isokinetic knee extension strength, isometric knee extension strength, isometric leg press strength, and isotonic leg press power were assessed in 17 individuals. Subjects performed 4 self-selected pace performance tests on a ladder ergometer (480 total rungs) and a motorized treadmill (10 km) while wearing a weighted suit under mock conditions (0%, suit fabric only) and with 40%, 60%, and 80% of their BW added. Survival curves were plotted for intermediate check points and completion under each condition, and performance to BW curves were generated. RESULTS: Percentage of subjects that completed the half-way point and end point, respectively, for the ladder were as follows: 100% and 100% for the mock load; 100% and 93% for 40% BW load, 100% and 79% for 60% load; and 69% and 62% for 80% load. Percentage of subjects that completed 5 km and 10 km, respectively, for the treadmill were as follows: 100% and 100% for the mock load; 93% and 79% for 40% BW load, 64% and 29% for 60% load; and 8% and 0% for 80% load. Scatter plots for aerobic capacity to BW (including external load) and muscle performance measures to BW versus ladder and treadmill performance reveal the laboratory metric to performance relationships. CONCLUSIONS: Manipulation of strength to BW using a weighted suit affects task performance and can be used to define the relationships between altered capabilities and task performance outcomes.

Muscle Co-contractions Worsen In The ACL Reconstructed Limb When Gait Is Challenged Compared To Normal Gait

PURPOSE: Greater and more symmetrical IKEM predict better functional outcomes after anterior cruciate ligament reconstruction (ACLR). Challenging walking tasks create greater internal knee extensor moments (IKEM) than normal walking after ACLR. Exploring muscle activity during normal and challenging walking could elucidate the underlying muscle responses to increased knee moments. METHODS: Three females (5-12 months post ACLR) who were cleared to return to sports participated. Subjects first completed normal walking followed by walking with a 50% body weight load while towing a sled and wearing a weighted vest. Order of the loaded conditions was randomized. Muscle activity of the medial and lateral quadriceps and hamstrings was measured bilaterally with surface electrodes (Fig 2). Walking speed was controlled. IKEM impulses and muscle activity while generating an IKEM were calculated during the stance phase of the task. Integrated electromyography (EMG) data were normalized to maximal EMG activity during a voluntary isometric contraction (MVIC). RESULTS: Descriptive statistics demonstrate that IKEM impulses and quadriceps activity increased when challenged (vest and sled) compared to normal walking. (Fig 1 and 2) EMG activity was greater in the ACLR limb across tasks, though the confidence intervals were large. (Fig 2) Though the small sample size was not powered to determine statistical significance, the greater magnitude of co-contraction activity in the ACLR limb was apparent for all females across all walking tasks. CONCLUSION: Quadriceps muscle activity increased along with IKEM impulses as expected. The asymmetrical muscle activity and large magnitude of hamstring activity was not expected. High levels of muscle co-contractions to achieve greater IKEM in the ACLR limb in these females is concerning.

EMG of Trunk and Lower Limb Muscles While Squatting with Different Stability and Resistance

PURPOSE: To determine the effects of squat with different stability and resistance on muscle activities. METHODS: Fourteen healthy male (age: 21 ± 2 years old, height: 176 ± 5 cm, and mass: 71 ±8 kg) performed squat. A VICON motion-analysis system was used for data collection. The RMS of EMG of rectus abdominis (RA), tensor fasciae latae (TFL), rectus femoris (RF), right tibialis anterior (RTA), left tibialis anterior (LTA),lower lumbar erector spinae (LLES), right gluteus maximus (RGMa),left gluteus maximus (LGMa), gluteus medius (GMe), and biceps femoris (BF) muscles were collected by a Trigno TM wireless EMG system when performing squat on a new six degrees of freedom platform (CAREN, with one stable and two level(A,B) of instability condition) under body weight and 30%RM(repetition maximum), respectively. The sequence of 6 conditions (SO, S30, A0, A30, BO, B30) for each subject was randomized to eliminate the possible fatigue and learning effects. A Polar heart rate monitor was applied to make sure heart rate under 100 b/min after each rest. Differences in EMG activities of the muscles were compared between S0 and the other conditions using the paired t-test. RESULTS: No significant difference was observed for most muscles EMG between unstable and stable surface (p>.05). Most of muscles EMG significantly increased when 30%RM weight load compared with the body weight load condition (p<.05, Table 1). CONCLUSIONS: Simply applying moderately unstable surface do not provide more stimulation to the superficial muscles, external weight load can effectively mobilize more muscle activity during squatting in highly resistance-trained people. The effects of external loading might not be replaced by unstable surface if the goal is to increase superficial muscle activation levels.TABLE 1: The Relative value (mean ± SD) of RMS of tested muscles under 6 conditions (N = 14)

High Fat Diet‐Induced Alterations in Alternative Splicing of Pre‐mRNA

Previous studies have shown that the pattern of alternative splicing of the fast troponin T (Tnnt3) pre‐mRNA in gastrocnemius muscle is directly proportional to increases in both experienced body mass (i.e. actual body weight plus additional external load) and muscle force production. However, this proportionality is disrupted in obese Zucker rats, such that the muscle of obese rats expresses Tnnt3 splice forms typically observed in smaller animals. The objective of the present study was to assess the time course of development of the obesity‐induced impairment of Tnnt3 pre‐mRNA alternative splicing as a prelude to delineating the molecular mechanism(s) involved in the response. In this study, obesity‐prone Sprague Dawley rats were placed on either a control or a high‐fat diet (HFD) for up to 8 wk. There was no significant difference in body weight in rats fed the HFD compared to the control diet. However, the pattern of Tnnt3 pre‐mRNA alternative splicing was altered after only 1 wk of consuming the HFD, such that there was a mismatch between body weight and the relative abundance of Tnnt3 splice forms. Moreover, the mismatch in alternative splicing worsened with increasing time on the HFD. For example, the relative abundance of Tnnt3 pre‐mRNA present in α‐splice forms increased with increasing body weight in rats fed the control but not the HFD. Furthermore, exon array analysis identified a significant number of other pre‐mRNAs that were alternatively spliced in the gastrocnemius in response to consuming the HFD for 8 wk. Overall, the results indicate that early changes in alternative splicing associated with feeding a HFD occur prior to changes in body weight and thus are likely a direct effect of the diet. (supported by NIH grant DK094141)

Implications of Dietary Leucine on Muscle mTOR Gene Expression and Redox Status in Rats Following High Intensity Effort

Leucine supplementation exerts a positive effect on mTOR pathway that is involved in the synthesis of skeletal muscle protein. In the present study, the capability of a 15-day dietary leucine supplementation (310 mg/kg) to improve the performance in acute high intensity effort and the inductive capacity on skeletal muscle protein anabolism in rats submitted to swimming exercise with a 10% bodyweight load attached to the tail, were studied. A 1.83-fold increase in mTOR gene expression in the treated group was found, while no changes in muscle protein content and rats body weight were observed. An increase in protein oxidation and a significant decrease in catalase were found in treated rats, while no changes in DNA damage, GSH and SOD levels were reported. We found an increase of superoxide anion and hydrogen peroxide/myeloperoxidase system in polymorphonuclear neutrophils obtained by treated group. These outcomes suggest slight enhancement in basal inflammation due to exercise activity via mTOR activation during treatment, without serious impairment of the antioxidant system and cell status. In conclusion, the 15-day leucine supplementation at the given dose, enhanced mTOR gene expression in the presence of acute effort which was also well tolerated by skeletal muscle, but probably too short to improve its anabolic activity. Keywords: Antioxidant enzymes, comet assay, leucine, mTOR gene expression, respiratory burst.

Effect of exercise at light loads with manipulative resistance on infraspinatus, trapezius (upper fiber) and deltoid (middle fiber) muscle activities in shoulder joint elevation.

[Purpose] To clarify rotator cuff muscular activity in the raised position of the closed kinetic chain (CKC) exercise. [Subjects] Twenty-nine cases were studied, 19 men and 10 women (average age 21.5 ±4.7 years old, average body weight 60.1 kg ±11.4). [Methods] To determine the effects of the closed kinetic chain exercise on the upper limb, we measured the surface EMG of the infraspinatus muscle, the trapezius (upper fiber) and the deltoid (middle fiber) with the arm elevated. [Results] Our results show that at an elevation angle of 150° in the scapular plane of the upper limb, with 5% body weight load, the EMG activities of the infraspinatus muscle are approximately 30% of maximum voluntary contraction (MVC). [Conclusion] The raised position of the CKC exercise is effective in physical therapy for functional recovery of the infraspinatus muscle.