Maximal Volitional Contraction Research Articles

New Zealand blackcurrant extract enhances muscle oxygenation during repeated intermittent forearm muscle contractions in advanced and elite rock climbers

Anthocyanin-rich New Zealand blackcurrant (NZBC) may improve forearm muscle oxygenation and enhance performance in high-level rock climbers. As such, using a double-blind, randomised, cross-over design study, twelve participants performed an oxidative capacity assessment, and two successive exhaustive exercise trials (submaximal forearm muscle contractions at 60% of their maximal volitional contraction). Each visit was conducted following 7-days intake of 600 mg·day−1 NZBC extract or placebo. Oxidative capacity was estimated by calculating the oxygen half time recovery using near infrared spectroscopy. Time to exhaustion (s), impulse (kg·s), and minimum tissue saturation index (min-TSI %) were assessed during both the exercise trials. Muscle oxidative capacity was greater with NZBC (mean difference [MD] = 5.3 s, 95% confidence intervals [95% CI] = 0.4–10.2 s; p = 0.036; Cohen’s d = 0.94). During the exercise trials, there was an interaction for min-TSI % (time x condition, p = 0.046; = 0.372), which indicated a greater level of oxygen extraction during trial two with NZBC extract (MD = 9%, 95% CI = 2-15%) compared to the placebo (MD = 2%, 95% CI = 1–7%). There was a decrease in time to exhaustion (p <0.001, = 0.693) and impulse (p = 0.001, = 0.672) in exercise trial two, with no effect of NZBC extract. In high-level rock climbers 7-days NZBC extract improves forearm muscle oxygenation with no effect on isolated forearm muscle performance.

Safety And Feasibility Of Strength Training In Patients With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a rapidly progressive and currently incurable neuromuscular disease. Understanding the role of exercise is important for these patients as high-intensity or eccentric actions can be damaging in DMD yet a lack of loading may exacerbate muscle dysfunction. While a few studies show submaximal exercise may be safe and potentially delay the loss of muscle function in DMD, no study has systematically examined the potential of strengthening exercise to improve muscle function or attenuate disease progression. PURPOSE: To examine the safety and feasibility of a pilot, in-home strengthening intervention consisting of knee extensor (KE) and flexor (KF) exercise in DMD. METHODS: Eight ambulatory boys with DMD [9.3 (0.8) yrs, BMI 19.0 (4.6) kg/m2] on corticosteroid therapy were recruited to undergo 12 weeks of isometric exercise training of the bilateral KE and KF. Exercise prescription consisted of 4 sets x 6 reps, 3x/week at a target intensity of 50% maximal volitional contraction (MVC). At baseline (BL), MVC testing and training familiarization were done for one week on site. The exercise equipment (custom built chair, laptop, and load cell) was subsequently shipped allowing for in-home training and supervision via live video conferencing for each session. Safety outcome measures to assess muscle damage included magnetic resonance proton transverse relaxation time (T2) of KE and KF, pain assessment, and creatine kinase levels at BL, 1, 6, and 12wks. Peak strength (KE and KF MVC) and time to ascend/descend 4 steps were also assessed at BL and 12wks. RESULTS: The 7 boys who completed the strength training program had a compliance of 84.9 (9.0)% for the exercise sessions. The safety measures did not indicate signs of muscle damage [non-significant change in mean T2: KE=2.3 (3.6)% and KF= 0.4 (4.6)%]. Peak torque increased by 20.6% for KE (p<0.01) and 14.3% for KF (p<0.05), and the time to ascend (13.5%, p<0.05) and descend (22.7%, p<0.05) steps improved after exercise training. CONCLUSION: This in-home, 12-week supervised strength training program was safe, feasible, and improved strength and function in boys with DMD. Future research is required to optimize the strengthening protocol and further explore its potential efficacy and clinical application.

TRPV1 and BDKRB2 receptor polymorphisms can influence the exercise pressor reflex.

The mechanisms responsible for the high inter-individual variability in blood pressure responses to exercise remain unclear. Common genetic variants of genes related to the vascular transduction of sympathetic outflow have been investigated, but variants influencing skeletal muscle afferent feedback during exercise have not been explored. Single nucleotide polymorphisms in TRPV1 rs222747 and BDKRB2 rs1799722 receptors present in skeletal muscle were associated with differences in the magnitude of the blood pressure response to static handgrip exercise but not mental stress. The combined effects of TRPV1 rs222747 and BDKRB2 rs1799722 on blood pressure and heart rate responses during exercise were additive, and primarily found in men. Genetic differences in skeletal muscle metaboreceptors may be a risk factor for exaggerated blood pressure responses to exercise. Exercise blood pressure (BP) responses demonstrate high inter-individual variability, which could relate to differences in metabolically sensitive afferent feedback from the exercising muscle. We hypothesized that single-nucleotide polymorphisms (SNPs) in genes encoding metaboreceptors present in group III/IV skeletal muscle afferents can influence the exercise pressor response. Two hundred men and women underwent measurements of continuous BP and heart rate at baseline and during 2min of static handgrip exercise (30% maximal volitional contraction), post-exercise circulatory occlusion and mental stress (serial subtraction; internal control). Participants were genotyped for SNPs in TRPV1 (rs222747; G/C), ASIC3 (rs2288645; G/A), BDKRB2 (rs1799722; C/T), PTGER2 (rs17197; A/G) and P2RX4 (rs25644; A/G). Exercise systolic BP (19± 10 vs. 22± 10mmHg, P= 0.03) was lower in GG versus GC/CC minor allele carriers for TRPV1 rs222747, while exercise diastolic BP (14± 7 vs. 17± 7mmHg, P= 0.007) and heart rate (12± 8 vs. 15± 9beatsmin-1 , P= 0.03) were lower in CC versus CT/TT minor allele carriers for BDKRB2 rs1799722. Individuals carrying both minor alleles for TRPV1 rs222747 and BDKRB2 rs1799722 had greater systolic (22± 11 vs. 17± 10mmHg, P= 0.04) and diastolic (18± 7 vs. 14± 7mmHg, P= 0.01) BP responses than those with no minor alleles; these differences were larger in men. No differences in BP or heart rate responses were detected during static handgrip with ASIC3 rs2288645, PTGER2 rs17197 or P2RX4 rs25644. None of the selected SNPs were associated with differences during mental stress. These findings demonstrate that variants in TRPV1 and BDKRB2 receptors can contribute to BP differences during static exercise in an additive manner.

A randomized controlled trial comparing home-based isometric handgrip exercise versus endurance training for blood pressure management

Aerobic endurance exercise (AEX) is an effective treatment in the prevention and management of high blood pressure (BP). Growing evidence suggests potential benefits from isometric handgrip (IHG) exercise, which may promote similar or even larger reductions in BP than AEX. We compared the effects of home-based AEX and home-based IHG on BP. Sixty healthy individuals (31 men; mean age, 33.1 years; mean BP, 126.9 ± 1.6/84.7 ± 1.1 mm Hg) were randomized to IHG, AEX, or a control group. Both exercise interventions were performed in the home environment. The IHG group performed daily 4 × 2 minutes sustained grips at 30% of maximal volitional contraction. Participants in the AEX group were advised to perform at least 150 min/wk of aerobic exercise at moderate intensity. Outcome measurements were assessed at baseline and 8 weeks of follow-up. Compared with the control group, AEX resulted in a larger reduction in ambulatory BP; both AEX and IHG exercise tended to induce larger reductions in office systolic BP, and office diastolic BP was significantly more reduced after AEX but not IHG exercise. Responses to training were not significantly different between both the exercise interventions. Eight weeks of home-based AEX results in significant reductions in both ambulatory BP and office BP in healthy adults, whereas IHG reduces only office BP.

Reliability of oscillometric central blood pressure responses to lower limb resistance exercise

Background and aimsAlthough it is well known that resistance training (RT) is beneficial for patients suffering from a variety of cardiovascular diseases, it remains underutilized as a rehabilitation tool as there is no reliable way to monitor the additional stress placed on the central organs. The current study aimed to determine between-day reliability of central haemodynamic indices using oscillometric pulse wave analysis (PWA) during progressive sub-maximal RT. MethodsNineteen healthy young males were tested on 3 different mornings in a fasted state. Central hemodynamic variables including augmentation index (AIx), AIx normalized to a heart rate of 75 beats per minute (AIx@75), central systolic blood pressure (cSBP), forwards (Pf) and backwards (Pb) wave reflection were determined at rest, as well as during leg extension RT at 10, 15 and 20% of maximal volitional contraction (MVC), and following 1 min and 5 min passive recovery. ResultsDuring RT at 10, 15 and 20% MVC, the intraclass correlation coefficient (ICC) values for AIx@75 (0.76–0.9), cSBP (0.74–0.78), Pf (0.75–0.82) and Pb (0.75–0.83) exceeded the criteria (0.75) for excellent reliability. During the 5 min recovery, the ICC values for AIx@75 (0.87–0.87), cSBP (0.69–0.7), Pf (0.63–0.67) and Pb (0.63–0.66) indicated good to excellent reliability. ConclusionsClinically meaningful changes in central hemodynamic indices can be obtained during resistance training using oscillometric PWA devices. This technology holds potential for advancing resistance training prescription guidelines for patients with overt cardiovascular diseases.

Differences in forearm strength, endurance, and hemodynamic kinetics between male boulderers and lead rock climbers

This study examined differences in the oxygenation kinetics and strength and endurance characteristics of boulderers and lead sport climbers. Using near infrared spectroscopy, 13-boulderers, 10-lead climbers, and 10-controls completed assessments of oxidative capacity index and muscle oxygen consumption (m⩒O2) in the flexor digitorum profundus (FDP), and extensor digitorum communis (EDC). Additionally, forearm strength (maximal volitional contraction MVC), endurance (force–time integral FTI at 40% MVC), and forearm volume (FAV and ΔFAV) was assessed. MVC was significantly greater in boulderers compared to lead climbers (mean difference = 9.6, 95% CI 5.2–14 kg). FDP and EDC oxidative capacity indexes were significantly greater (p = .041 and .013, respectively) in lead climbers and boulderers compared to controls (mean difference = −1.166, 95% CI (−3.264 to 0.931 s) and mean difference = −1.120, 95% CI (−3.316 to 1.075 s), respectively) with no differences between climbing disciplines. Climbers had a significantly greater FTI compared to controls (mean difference = 2205, 95% CI= 1114–3296 and mean difference = 1716, 95% CI = 553–2880, respectively) but not between disciplines. There were no significant group differences in ΔFAV or m⩒O2. The greater MVC in boulderers may be due to neural adaptation and not hypertrophy. A greater oxidative capacity index in both climbing groups suggests that irrespective of climbing discipline, trainers, coaches, and practitioners should consider forearm specific aerobic training to aid performance.

A Systematic Review of Rehabilitation Exercises to Progressively Load the Gluteus Medius.

Gluteus medius rehabilitation is of critical importance given its role in pelvic and lower limb stability, and the known link between gluteus medius weakness and many lower limb conditions. To systematically review the literature and present an evidence-based graduated series of exercises to progressively load gluteus medius. A systematic literature search was conducted in January 2016 to identify studies reporting gluteus medius muscle activity as a percentage of maximal volitional isometric contraction (MVIC), during rehabilitation exercises. Studies that investigated injury free participants were included. No restrictions were placed on the type or mode of exercise, though exercises that could not be accurately replicated or performed within an independent setting were excluded. Studies that did not normalize electromyographic activity to a side lying MVIC were excluded. Exercises were stratified based on exercise type and %MVIC: low (0% to 20%), moderate (21% to 40%), high (41% to 60%), and very high (> 61%). 20 studies were included in this review, reporting outcomes in 33 exercises (and a range of variations of the same exercise). Prone, quadruped, and bilateral bridge exercises generally produced low or moderate load. Specific hip abduction/rotation exercises were reported as moderate, high, or very high load. Unilateral stance exercises in the presence of contralateral limb movement were often high or very high load activities, while high variability existed across a range of functional weight-bearing exercises. This review outlined a series of exercises commonly employed in a rehabilitation setting, stratified based on exercise type and the magnitude of gluteus medius muscular activation. This will assist clinicians in tailoring gluteus medius loading regimens to patients, from the early postoperative through to later stages of rehabilitation.

Oxygen recovery kinetics in the forearm flexors of multiple ability groups of rock climbers.

The purpose of this study was to determine muscle tissue oxidative capacity and recovery in intermediate, advanced, and elite rock climbers. Forty-four male participants performed (a) sustained and (b) intermittent contractions at 40% of maximal volitional contraction (MVC) on a sport-specific fingerboard until volitional fatigue. Near-infrared spectroscopy was used to assess muscle tissue oxygenation during both the exercise and the 5-minutes passive recovery period, in the flexor digitorum profundus (FDP) and flexor carpi radialis (FCR). During the sustained contraction only, muscle tissue deoxygenation (O2 debt) in the FDP and FCR was significantly greater in elite climbers compared with the control, intermediate, and advanced groups (FDP: 32 vs. 15, 19, 22%; FCR: 19 vs. 11, 8, 15%, respectively). However, elite climbers had a significantly quicker time to half recovery (T1/2) than the control and intermediate groups in the FDP (8 vs. 95 and 47 seconds, respectively) and the FCR (7 vs. 30 and 97 seconds, respectively) because the O2% recovered per second being significantly greater (FDP: 4.2 vs. 0.7 and 0.3; FCR: 4.8 vs. 0.1 and 0.2, respectively). Furthermore, during the intermittent contraction, T1/2 in elite climbers was significantly quicker compared with the control and intermediate groups in the FDP (8 vs. 93 and 83 seconds, respectively) and FCR (16 vs. 76 and 50 seconds, respectively). Consequently, lower-level climbers should focus training on specific intermittent fatigue protocols. Competition or elite climbers should make use of appropriate rests on route to aid recovery and increase the chances of reaching the next hold.

Interaction of gender and body composition on rectus femoris morphology as measured with musculoskeletal ultrasound imaging.

Background:Quadriceps function is an important measure in patients recovering postoperatively. Traditionally, strength measures that require high levels of resistance are contraindicated during the early postoperative phase. Thus it may be helpful to evaluate the utilization of other tools, such as ultrasound imaging, that allow for assessment during a position of low resistance.Hypothesis:The rectus femoris cross-sectional area (CSA) is affected by sex and body composition in healthy subjects.Study Design:Cross-sectional study.Level of Evidence:Level 4.Methods:Thirty-two healthy subjects (16 women, 16 men), selected from a previously larger study, were chosen for analysis. All subjects underwent a maximal volitional isometric contraction protocol from 0° to 90° of knee motion controlled by an isokinetic dynamometer. In the contracted and resting positions, the rectus femoris CSA was measured at each angle using ultrasound imaging. The contractile index (contracted − resting CSA) was calculated at each position. Subjects were separated into 1 of 4 groups based on sex and fat percentage (low or high). These data were analyzed using mixed-factor analysis of variance (group × angle) for each variable, with a critical α level of 0.05.Results:A significant interaction was noted for the CSA of the rectus femoris at rest (P < 0.03) and during contraction (P < 0.02). For both variables, all groups performed similarly, with the exception of women with high body fat percentage. No statistically significant interaction existed for the contractile index; however, a main effect for angle (P < 0.01) was observed.Conclusion:Rectus femoris CSA appears to depend on sex as well as the body composition of individuals.Clinical Relevance:Traditional subjective assessment measures of quadriceps strength and function have low reliability and functional validity. With the improved feasibility of ultrasound imaging in the clinical setting, quadriceps size may be more accurately measured during the early postoperative stages.

Changes in predicted muscle coordination with subject-specific muscle parameters for individuals after stroke.

Muscle weakness is commonly seen in individuals after stroke, characterized by lower forces during a maximal volitional contraction. Accurate quantification of muscle weakness is paramount when evaluating individual performance and response to after stroke rehabilitation. The objective of this study was to examine the effect of subject-specific muscle force and activation deficits on predicted muscle coordination when using musculoskeletal models for individuals after stroke. Maximum force generating ability and central activation ratio of the paretic plantar flexors, dorsiflexors, and quadriceps muscle groups were obtained using burst superimposition for four individuals after stroke with a range of walking speeds. Two models were created per subject: one with generic and one with subject-specific activation and maximum isometric force parameters. The inclusion of subject-specific muscle data resulted in changes in the model-predicted muscle forces and activations which agree with previously reported compensation patterns and match more closely the timing of electromyography for the plantar flexor and hamstring muscles. This was the first study to create musculoskeletal simulations of individuals after stroke with subject-specific muscle force and activation data. The results of this study suggest that subject-specific muscle force and activation data enhance the ability of musculoskeletal simulations to accurately predict muscle coordination in individuals after stroke.

P42 Does pulmonary rehabilitation improve exercise capacity and HRQoL in patients with asthma?

IntroductionPulmonary rehabilitation (PR) benefits patients with COPD, however to date there is limited evidence demonstrating its effectiveness in patients with chronic asthma.We hypothesised that patients with asthma would have a...

GW24-e0010 Study of Bushenhuoxue Granules on tension of biceps brachii of patients with Parkinson's disease

ObjectivesTo study the effects of Bushenhuoxue Granules on biceps brachii tension in Patients with Parkinson’s disease. MethodsTotally 102 patients were enrolled and divided into two groups randomly, 50 patients in...

Quadriceps Activation Failure After Anterior Cruciate Ligament Rupture Is Not Mediated by Knee Joint Effusion

Descriptive prospective cohort study. To investigate the relationships between knee joint effusion, quadriceps activation, and quadriceps strength. These relationships may help clinicians better identify impaired quadriceps activation. After anterior cruciate ligament (ACL) injury, the involved quadriceps may demonstrate weakness. Experimental data have shown that quadriceps activation and strength may be directly mediated by intracapsular joint pressure created by saline injection. An inverse relationship between quadriceps activation and the amount of saline injected has been reported. This association has not been demonstrated for traumatic effusion. We hypothesized that traumatic joint effusion due to ACL rupture and postinjury quadriceps strength would correlate well with quadriceps activation, allowing clinicians to use effusion and strength measurement as a surrogate for electrophysiological assessment of quadriceps activation. Prospective data were collected on 188 patients within 100 days of ACL injury (average, 27 days) referred from a single surgeon. A complete clinical evaluation of the knee was performed, including ligamentous assessment and assessment of range of motion and effusion. Quadriceps function was electrophysiologically assessed using maximal volitional isometric contraction and burst superimposition techniques to quantify both strength and activation. Effusion grade did not correlate with quadriceps central activation ratio (CAR) (zero effusion: mean ± SD CAR, 93.5% ± 5.8%; trace effusion: CAR, 93.8% ± 9.5%; 1+ effusion: CAR, 94.0% ± 7.5%; 2+/3+ effusion: CAR, 90.6% ± 11.1%). These values are lower than normative data from healthy subjects (CAR, 98% ± 3%). Joint effusion after ACL injury does not directly mediate quadriceps activation failure seen after injury. Therefore, it should not be used as a clinical substitute for electrophysiological assessment of quadriceps activation. Patients presenting to physical therapy after ACL injury should be treated with high-intensity neuromuscular electrical stimulation to help normalize this activation.

Whole-body vibration strengthening compared to traditional strengthening during physical therapy in individuals with total knee arthroplasty

ABSTRACTThis study investigated the use of whole-body vibration (WBV) as an alternative strengthening regimen in the rehabilitation of individuals with total knee arthroplasty (TKA) compared with traditional progressive resistance exercise (TPRE). Individuals post TKA (WBV n = 8; TPRE n = 8) received physical therapy with WBV or with TPRE for 4 weeks. Primary dependent variables were knee extensor strength, quadriceps muscle activation, mobility, pain, and range of motion (ROM). There was a significant increase in knee extensor strength and improvements in mobility, as measured by maximal volitional isometric contraction and the Timed Up and Go Test (TUG), respectively, for both groups (p < 0.01). The WBV knee extensor strength improved 84.3% while TPRE increased 77.3%. TUG scores improved 31% in the WBV group and 32% for the TPRE group. There were no significant differences between groups for strength or muscle activation (Hotelling's T2 = 0.42, p = 0.80) or for mobility (F = 0.54; p = 0.66). No adverse side effects were reported in either group. In individuals with TKA, both WBV and TPRE showed improved strength and function. Influence of WBV on muscle activation remains unclear, as muscle activation levels were near normal for both groups.

Heightened Flexor Withdrawal Responses in Subjects With Knee Osteoarthritis

Patients with osteoarthritic (OA) knee pain often present with impaired muscle activation and function that may be attributed in part to hyperexcitability of flexion withdrawal reflexes (FWRs). The aim of this study was to investigate alterations in the excitability of FWR in individuals with knee OA and its potential associations with impaired quadriceps activation (QA) and subjective reports of pain. Twenty subjects with and 20 without knee OA (age, 45 to 75 years) participated. Impaired QA was determined in OA subjects during maximal volitional contraction of the quadriceps. FWRs were tested in isometric conditions using electrocutaneous stimulation applied at the medial foot at 1x and 2x FWR threshold and surface electromyographic recordings obtained from tibialis anterior (TA) and biceps femoris (BF). Joint torques at the hip, knee, and ankle were calculated and normalized to body mass. FWR threshold was significantly diminished in OA versus the control group (P < .01). In addition, FWR latencies were consistent with spinally mediated responses, with significantly earlier responses in OA versus control subjects of TA at threshold (P = .002) and BF at suprathreshold stimulation (P = .0006). Impaired QA was found in 4 of 20 OA subjects but was not correlated to FWR threshold or pain levels. Peak joint torques were diminished in the OA versus the control group (P < .0006). Increased excitability of FWRs was evident in subjects with chronic knee osteoarthritis, including those subjects without resting pain, but was not associated with impaired QA. Management strategies for this patient population must consider altered pain processing in addition to addressing impairments found at the knee.

Constant Wrist Extension Force Decreases Extensor Carpi Radialis Activity With Gripping

The extensor capri radialis (ECR) muscle is commonly associated with tennis elbow (TE). When an individual grips an object such as a tennis racket, the ECR muscle functions to counter the finger flexors' duel functions as an isometric finger flexor/wrist flexor. Previous research indicates the ECR is a compensating wrist extension counter-moment during gripping. Exploring ways to lessen the muscles activity of the ECR during gripping tasks, such as playing tennis, could be beneficial. PURPOSE: To determine the influence of a wrist extension moment on ECR activity when gripping a tennis racket handle. METHODS: Twenty injury free participants, (10 male, 10 female), volunteered for this study (Age = 23.67 + 2.36 years). The skin was properly prepped then surface electromyography (EMG) electrodes were placed over the ECR of the dominant arm. A reference maximal volitional isometric contraction (MVIC) of the ECR during gripping of a tennis racket handle (racket head removed) was performed. ECR activity of Grip condition (G) was obtained by participants gripping an intact tennis racket with the instruction of using normal tennis racket grip force. The reference grip force, obtained in condition G, was measured using finger force transducers. Grip Wrist Moment condition (GWM) was obtained by instructing participants to replicate the grip force of condition G (within 5%) on a tennis racket handle with an added wrist extension moment to the wrist (Grip Wrist Moment). A dependant samples t-test was utilized to compare %MVIC of conditions G and GWM. RESULTS: A significant decrease was noted in % MVIC of the ECR from G to GCM conditions (G = 20.8 MVIC + 12%, GWM = 13.9 MVIC + 14.7%)(p < 0.05). CONCLUSIONS: The results suggest that applying an external wrist extension influence could lessen the activity of the ECR muscle during functional gripping, which has many implications for tennis players trying to rehabilitate from lateral epycondylitis (tennis elbow). The design of sporting equipment, containing a constant wrist extension force to lessen ECR activity while playing, would be beneficial to many athletes.

Relationship between erector spinae muscle oxygenation via in vivo near infrared spectroscopy and static endurance time in healthy males

The purpose of the study was to confirm the trends in right and left side muscle blood volume (Mbv) and muscle oxygenation (Mox) during the Biering-Sorensen muscular endurance (BSME) test, compare right and left side Mbv and Mox responses, and predict BSME time via Mox variables. Research suggests that during moderate intensity (approximately 20% of maximal volitional contraction) muscle contraction blood flow will decrease as a result of increased intramuscular pressure. Moreover, decreased muscle oxygenation is believed to be associated with diminished musculoskeletal endurance time, but until the development of near infrared spectroscopy (NIRS) it was not possible to non-invasively monitor these changes in erector spinae muscle. Nineteen healthy males completed the BSME in a prone position. The NIRS probes were placed on the left and right erector spinae muscle at the third lumbar vertebra level. The test protocol was: 2 min resting baseline, BSME to volitional fatigue, and 4 min recovery. The results indicated Mbv initially increased reaching asymptote before returning to baseline at termination. The Mox increased then declined systematically until BSME termination, returning to near baseline in recovery. No significant difference between sides was noted for Mbv or Mox. Mox best predicted BSME time. In conclusion, Mbv increased and then reaches asymptote as indicated in previous research, and oxygen availability was associated with the duration of erector spinae static contraction. Thus, prolonged static postures using the erector spinae muscles may diminish muscle oxygenation increasing susceptible to fatigue and injury.

Accuracy of predicting maximal quadriceps force from submaximal effort contractions after anterior cruciate ligament injury

Weakness and failure of voluntary activation of the quadriceps femoris muscles often occur after anterior cruciate ligament (ACL) rupture. Side-to-side strength comparisons are used as a measure of progress, and are inaccurate if the quadriceps has activation failure. Burst superimposition testing is commonly used to assess quadriceps strength and activation during a maximal volitional isometric contraction (MVIC), using the central activation ratio (CAR) calculation. A recently developed mathematical model predicts the MVIC from submaximal efforts. The purpose of this study was to compare the CAR calculation to the mathematical model. We hypothesized that the model would be a more accurate predictor of strength than the CAR calculation when voluntary activation failure is present. Data from the involved and uninvolved quadriceps muscles of 100 consecutive subjects with complete, isolated ACL rupture were retrospectively evaluated. Subjects who required multiple trials to produce an MVIC with full activation (true MVIC) were used to compare the CAR calculation, the mathematical model, and this true MVIC. Subjects unable to produce a true MVIC with multiple trials were used to compare the mathematical model to the CAR calculation. Results demonstrate that both methods reliably and accurately estimate the quadriceps weakness associated with ACL rupture. We recommend use of the CAR calculation to provide estimations of true quadriceps strength to facilitate clinical decisions about progress in rehabilitation after ACL rupture.

Effect of a splint on measures of sustained grip exertion under different forearm and wrist postures

Despite the facts that gripping tasks have been found to be highly correlated with CTS and that splints are gaining popularity as personal protective equipment, the influence of splints on grip performance has not been determined adequately. The present study intends to investigate the influence of splints without the volar parts as well as of forearm and wrist postures on grip performances including maximal volitional contraction (MVC), maximum acceptable sustained time (MAST), cumulated exertion output (CEO), and normalized exertion level (NEL). Twenty college-student volunteers, 10 males and 10 females, were recruited. The factors of interest were gender, forearm position, wrist deviation, and splint (with and without). The forearm positions were set at 30° internal shoulder rotation, 0° internal shoulder rotation, and 30° external shoulder rotation, the angles being measured between the sagittal plane and the long axis of dominant forearm. The wrist deviations were extension 30°, neutral, and flexion 30°, the angles being measured between the sagittal plane and the long axis of the grip gauge. The results indicate that the gender effect is the most dominantly significant on all evaluated response variables. Males have more MVC (220 vs. 337 N), longer MAST (20.2 vs. 10.5 s), and greater CEO (4306 vs. 1638 N s), but less NEL (66.6 vs. 73.9 %MVC). The forearm posture is shown to be significant only on MVC. In addition, the effect of wrist posture cannot shift all responses, nor can the effect of splints. In general, a splint without volar part seems to be recommended while performing infrequent and forceful gripping tasks under the consideration of prevention, but there should be more information about the application of a splint without volar part while performing a repetitively gripping task.

THE EFFECT OF SPLINTS ON PEAK STRENGTH, SUSTAINING TIME, AND TOTAL FORCE GENERATION AT DIFFERENT PINCHING TYPES

ABSTRACT Present study intends to investigate the effects of wrist splints, pinch types (pulp 3, pulp 2, chuck, and lateral), and gender on pinching performance measured during a sustaining exertion, including maximal volitional contraction (MVC), maximal acceptable sustaining time (MAST), total force generation (TFG) over the MAST, and the normalized exertion level (NEL), defined as [TFG/(MASTxMVC)]x100. Twelve males and 12 females participated in this experiment, and a balanced nested-factorial design was employed. The ANOVA results indicate that the gender effect is significant in all areas but MAST, and this finding seems to imply that females exert less effectively and efficiently than males do. Pinch types affect all four responses significantly, and pinch types with higher MVC values have higher MAST, TFG, and NEL values as well; consequently, the two pinch types of chuck and lateral are recommended, but pulp 3 is not. Of interest, wearing splints did not affect all responses but significantly shortened the MAST value.