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Luiz Henrique Palucci Vieira, Felipe de Souza Serenza, Vitor Luiz de Andrade, Lucas de Paula Oliveira, Fábio Pamplona Mariano, Juliana Exel Santana and Paulo Roberto Pereira Santiago

The aims of the current study were to analyze a kick from 10 m in a futsal context and the parameters of muscular strength using an isokinetic dynamometer in a laboratory environment, performed with the dominant (DL) and nondominant lower limbs (NDL). Seventeen professional elite players participated. Kicking performance was evaluated from the second penalty mark. Next, athletes completed a strength evaluation with an isokinetic dynamometer at speeds of 60°⋅s–1, 180°⋅s–1, and 300°⋅s–1. Significant differences were observed for hip (15.64 ± 3.44; 13.97 ± 2.62), ankle (63.19 ± 8.90; 52.55 ± 8.72), foot (82.31 ± 7.93; 68.41 ± 7.85), and ball (99.74 ± 8.45; 88.31 ± 7.93) speeds (km⋅h–1), and average power at 180°⋅s–1 (325.59 ± 40.47; 315.79 ± 39.49 W), but not for accuracy (1.33 ± 0.57; 1.66 ± 0.77 m) between the DL and NDL, respectively. Few moderate correlations were observed in the DL (r = .54–.64) or NDL (r = .53–.55) between the kinematic variables of kick and muscular strength parameters (P < .05). We conclude that highly trained players present asymmetries in kicking motion; however, the imbalance in muscular strength is very small. We recommend that specific court tests be conducted to reliably characterize kicking performance in futsal. Success in kicking seems to be too variable and complex to be totally predicted only by joints, foot and ball speed, and lower limb muscular strength parameters.

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Frederick S. Daniels and Daniel M. Landers

This study investigated heart rate (HE) and respiration functioning during rifle shooting to test hypotheses derived from Schwartz's (1979) systems and disregulation theory, and to compare biofeedback with verbal instruction in developing awareness and control of autonomic patterns. Male subjects (N = 8) were pretested to determine HE and respiration patterns affecting performance. They were then divided into two equal groups and given either auditory biofeedback or verbal instruction. The auditory-biofeedback group received continuous pattern feedback through earphones while the verbal instruction group received only presession instruction without feedback. Each group trained for five sessions of 40 shots each. Following training, two 40-shot sessions were conducted. A scaled interview was administered pre- and posttraining to determine awareness/control of autonomic functioning. Compared to the verbal instruction group, the results showed that the biofeedback group significantly improved performance and consistency of the desired pattern and had significantly greater awareness/control of the autonomic pattern. The results supported the systems and disregulation theory as well as the viability of biofeedback for altering imbalances within the systems.

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Yin-Chou Lin, Angela Thompson, Jung-Tang Kung, Liang-Wei Chieh, Shih-Wei Chou and Jung-Charng Lin

Context:

Elbow injuries are widely reported among baseball players. The elbow is susceptible to injury when elbow-flexor and -extensor forces are imbalanced during pitching or throwing. Assessment of muscle-strength ratios may prove useful for diagnosing elbow injury.

Objective:

The purpose of this study was to assess the relationship between the elbow-flexor and -extensor functional isokinetic ratios and elbow injury in baseball players.

Design:

Retrospective study.

Setting:

Biomechanics laboratory.

Participants:

College baseball players with (n = 9) and without (n = 12) self-reported elbow pain or loss of strength were recruited.

Intervention and Main Outcome Measures:

Trials were conducted using a dynamometer to assess dominant-arm flexor and extensor concentric and eccentric strength at angular velocities of 60° and 240°/s. Functional isokinetic ratios were calculated and compared between groups.

Results:

Regression analysis revealed that a ratio of biceps concentric to triceps concentric strength greater than 0.76 (the median value) significantly predicted elbow injury (P = .01, odds ratio of injury = 24). No other ratios or variables (including position played) were predictive of injury status.

Conclusions:

These findings suggest that the ratio of biceps concentric to triceps concentric functional strength strongly predicts elbow-injury status in baseball players. Assessment of this ratio may prove useful in a practical setting for training purposes and both injury diagnosis and rehabilitation.

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Mark Kluemper, Tim Uhl and Heath Hazelrigg

Context:

Imbalanced shoulder muscles might cause poor posture in swimmers, which has been implicated as potential cause of injury.

Objective:

To determine whether a training program can reduce forward shoulder posture.

Design:

Prospective pseudorandomized.

Setting:

College swimming pool.

Participants:

39 competitive swimmers (age 16 ± 2 years) divided into an exercise group (n = 24) and a control group (n = 15).

Intervention:

The experimental group performed a partner-stretching program on the anterior shoulder muscles and a strengthening regimen focusing on the posterior shoulder muscles for 6 weeks. The control group participated in normal swim-training activities.

Main Outcome Measures:

Shoulder posture was measured as the distance from the anterior acromion to a wall using a double-square method.

Results:

The experimental group significantly reduced the distance of the acromion from the wall in a resting posture (–9.6 ± 7.3 mm) as compared with the control group (–2.0 ± 6.9 mm).

Conclusions:

A training routine might reduce the forward shoulder posture present in most competitive swimmers.

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Jean-Benoît Morin and Pierre Samozino

Recent studies have brought new insights into the evaluation of power-force-velocity profiles in both ballistic push-offs (eg, jumps) and sprint movements. These are major physical components of performance in many sports, and the methods the authors developed and validated are based on data that are now rather simple to obtain in field conditions (eg, body mass, jump height, sprint times, or velocity). The promising aspect of these approaches is that they allow for more individualized and accurate evaluation, monitoring, and training practices, the success of which is highly dependent on the correct collection, generation, and interpretation of athletes’ mechanical outputs. The authors therefore wanted to provide a practical vade mecum to sports practitioners interested in implementing these power-force-velocity–profiling approaches. After providing a summary of theoretical and practical definitions for the main variables, the authors first detail how vertical profiling can be used to manage ballistic push-off performance, with emphasis on the concept of optimal force–velocity profile and the associated force–velocity imbalance. Furthermore, they discuss these same concepts with regard to horizontal profiling in the management of sprinting performance. These sections are illustrated by typical examples from the authors’ practice. Finally, they provide a practical and operational synthesis and outline future challenges that will help further develop these approaches.

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Naryana Cristina Mascarin, Claudio Andre Barbosa de Lira, Rodrigo Luiz Vancini, Alberto de Castro Pochini, Antonio Carlos da Silva and Marilia dos Santos Andrade

Context:

Imbalance in shoulder-rotator muscles has been considered a risk factor for injuries in handball. Strength training programs (STPs) may play an important preventive role.

Objective:

To verify the effects of an STP using elastic bands on shoulder muscles and ball-throwing speed.

Design:

Randomized and prospective controlled trial.

Setting:

Exercise physiology laboratory.

Participants:

Thirty-nine female handball players were randomly assigned to an experimental (EG, n = 21, 15.3 ± 1.1 y) or a control (CG, n = 18, 15.0 ± 0.8 y) group.

Intervention:

The EG performed the STP with elastic-band progressive exercises for 6 wk before regular handball training, and the CG underwent only their regular training.

Main Outcome Measures:

Before and after the STP, both groups underwent a ball-throwing-speed test and isokinetic test to assess shoulder internal- (IR) and external-rotator muscle performance.

Results:

Average power values for IR muscles presented a significant group-vs-time interaction effect (F = 3.9, P = .05); EG presented significantly higher values after the STP (P = .03). Ball speed presented higher values in EG after the STP in standing (P = .04) and jumping (P = .03) throws. IR peak-torque values and balance in shoulder-rotator muscles presented no group-vs-time interaction effect.

Conclusions:

STP using elastic bands performed for 6 wk was effective to improve muscle power and ball speed for young female handball players.

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Pascal David, Mohamad Halimi, Isabelle Mora, Pierre-Louis Doutrellot and Michel Petitjean

Ankle sprains are among the most common sport-related injuries and can lead to chronic ankle instability. Impaired sensorimotor function of the ankle musculature is often suggested as a cause. The current study sought to assess and compare the isokinetic performance and electromyographic patterns of evertor and invertor muscles in patients with chronic ankle instability and in a control group. Twelve patients with chronic ankle instability and twelve healthy subjects were included. Isokinetic eccentric and concentric testing at various angular velocities was performed for eversion and inversion movements. The corresponding myoelectric activities of the fibularis longus and tibialis anterior muscles were quantified from surface electromyographic recordings by computing average root mean square values. Patients had lower myoelectric activity of the evertor and invertor muscles than controls did; this difference could account for the eccentric weakness associated with ankle instability. Functional strength ratios revealed a dynamic strength imbalance in unstable ankle patients and that may contribute to recurrent injury. Our findings suggest that rehabilitation programs for unstable ankle patients must be focused on the motor control of eccentric contractions of the ankle evertors and invertors, to boost these muscles’ contribution to ankle stabilization.

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Jeanne F. Nichols, Hilary Aralis, Sonia Garcia Merino, Michelle T. Barrack, Lindsay Stalker-Fader and Mitchell J. Rauh

There is a growing need to accurately assess exercise energy expenditure (EEE) in athletic populations that may be at risk for health disorders because of an imbalance between energy intake and energy expenditure. The Actiheart combines heart rate and uniaxial accelerometry to estimate energy expenditure above rest. The authors’ purpose was to determine the utility of the Actiheart for predicting EEE in female adolescent runners (N = 39, age 15.7 ± 1.1 yr). EEE was measured by indirect calorimetry and predicted by the Actiheart during three 8-min stages of treadmill running at individualized velocities corresponding to each runner’s training, including recovery, tempo, and 5-km-race pace. Repeated-measures ANOVA with Bonferroni post hoc comparisons across the 3 running stages indicated that the Actiheart was sensitive to changes in intensity (p < .01), but accelerometer output tended to plateau at race pace. Pairwise comparisons of the mean difference between Actiheart- and criterion-measured EEE yielded values of 0.0436, 0.0539, and 0.0753 kcal · kg−1 · min−1 during recovery, tempo, and race pace, respectively (p < .0001). Bland–Altman plots indicated that the Actiheart consistently underestimated EEE except in 1 runner’s recovery bout. A linear mixed-model regression analysis with height as a covariate provided an improved EEE prediction model, with the overall standard error of the estimate for the 3 speeds reduced to 0.0101 kcal · kg−1 · min−1. Using the manufacturer’s equation that combines heart rate and uniaxial motion, the Actiheart may have limited use in accurately assessing EEE, and therefore energy availability, in young, female competitive runners.

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Kent C. Hansen and Dale A. Schoeller

Objective:

Increasing fat content in an isocaloric diet is associated with positive fat imbalance. Exercise attenuates this process, and the authors hypothesized the attenuation was a result of altered postprandial lipid trafficking.

Design:

To investigate the effects of prior exercise and nutritional state on the metabolic fate of dietary fat, a study was designed with 4 treatment arms. Energy-balance modifications (fed or fasted) ± exercise were followed by postexercise feeding of 1-14C oleic acid to Sprague-Dawley rats. Fed rats were fed 6 hr before treatment, whereas fasted rats were fasted for 15 hr before treatment with the primary variable being exercise.

Measurements:

14C content of gastrointestinal tract, plasma, breath, muscle (soleus, vastus lateralis [VL], and extensor digitorum longus), liver, and adipose tissue (retroperitoneal and epididymal) was measured at 5 time points postdose (1, 2, 4, 8, and 24 hr).

Results:

Compared with matched unexercised controls, fed rats undergoing acute exercise significantly increased recovery of 14C in breath (p = .005) and plasma (p = .001), and trends of increasing 14C recovery occurred in VL (p = .07) and soleus (p = .06). Acute exercise significantly increased recovery of 14C in breath (p = .003), VL (p = .04), and soleus (p = .03) in the fasted study. Acute exercise significantly decreased the trafficking of dietary tracer into adipose tissue in only the fed study (p < .0001).

Conclusion:

Although the effect of acute exercise on trafficking dietary fat away from adipose tissue was greater in the fed group than in the fasted, acute exercise had beneficial effects on adipose tissue’s collecting dietary fat when fed or fasted.

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Rachele E. Vogelpohl and Roger O. Kollock

Context:

Shoulder injury in baseball pitchers is a very common problem and has been linked to an imbalance in rotator cuff strength. Recently, the use of functional shoulder strength ratios has become more popular because they more closely resemble the actions of the shoulder during the throwing motion.

Objective:

To investigate the link between preseason shoulder rotator cuff functional strength ratios and the development of shoulder pain and injury.

Design:

Prospective research design.

Setting:

University human performance laboratory.

Patients:

Fifteen collegiate baseball pitchers participated in this study. At the end of the baseball season, six (19.5 ± 1.8 years, 73.6 ± 2.8 inches, 198.7 ± 19.1 lbs) developed shoulder injury and were placed in the injured group, and nine (21.0 ± 1.7 years, 73.1 ± 2.3 inches, 207.9 ± 28.1 lbs) did not develop injury and were placed in the noninjured group.

Interventions:

Isokinetic peak torque was collected concentrically and eccentrically for both shoulder internal rotation (IR) and external rotation (ER) at 60°-s−1, 180°-s−1, and 300°-s−1.

Main Outcome Measure:

The following functional ratios were calculated from the peak torque measures: concentric ER: concentric IR; eccentric ER: eccentric IR; concentric ER: eccentric IR (cocking phase); and eccentric ER: concentric IR (acceleration phase). Analysis was conducted using an analysis of variance comparing the injured and noninjured groups. A secondary analysis was conducted using an analyses of variance on the concentric and eccentric peak torque for shoulder IR and ER between groups.

Results:

The acceleration phase functional shoulder ratio was significantly higher (p = .019) in the injured group and a concentric IR peak torque (p = .003) was significantly lower in the injured group compared with the noninjured group.

conclusion:

Increased acceleration phase ratios and decreased concentric IR peak torque may be linked to the development of shoulder injury during a baseball season.