Investigation of the effect of supramaximal eccentric contractions on muscle damage and recovery between the dominant and non-dominant arm

Tennis players develop asymmetric dimension of dominant or non-dominant arms. Since nutrients and trophic factors (such as insulin) are delivered through blood, we hypothesized that tennis training causes asymmetric blood distribution to arms is associated with this structural difference. In this study, nine young volunteers (age 19.8±0.5 years) were recruited for a session of high-frequency forehand tennis training (20 balls/min) for 10 min. Muscle blood distribution of the non-dominant and dominant arms was then determined by tissue hemoglobin (TH) concentrations using near-infrared spectroscopy (NIRS) during 2-day recovery period. The circumference of the arms of their racket hands (dominant arms) was greater than that of the opposite arms. Forearm oxygen saturation was significantly lower in both arms immediately after training, whereas, the dominant arm's oxygen saturation was significantly higher than that of the non-dominant arm one day after exercise. Oxygenated hemoglobin of the non-dominant arm was significantly lower immediately and also one day after exercise. Comparably, the dominant arm has higher oxygenated hemoglobin level than the non-dominant arm one day after training. In addition, the deoxygenated hemoglobin value of the dominant arm was significantly higher immediately after exercise. Before training, no difference in TH was found between arms. However, dominant arm showed higher TH concentrations than the nondominant arm immediately after training and continued to day-1. TH concentration of the non-dominant arm was significantly lower one day-1 after tennis training compared to baseline. These results of the study provide a potential basis that might explain the asymmetric development of arm size in professional tennis players.

Muscular imbalances may increase the risk of injury and decrease physical performance. Conventional wisdom suggests dominant side musculature may be more developed owing to preferred usage. Quantifying muscle imbalance between non-dominant and dominant arms is facilitated by technology that permits the measurement of arm power output across a range of resistances. PURPOSE: To compare power output achieved by the dominant and non-dominant arms under various load conditions. METHODS: 18 females and 14 males (21.0 ± 2.3 years, 66.9 ± 4.3 inches, 168.3 ± 36.2 lbs) were enrolled into an optimal muscle loading program using Proteus (Proteus Motion, USA). Each subject performed the following ten movements: abduction, adduction, external rotation, internal rotation, biceps curl, triceps extension, horizontal push, horizontal row, vertical push, and vertical row. Each movement was repeated twice under four separate loads: 7lb, 14lb, 21lb, and 28lb. Maximum average power for each movement was recorded in watts for further analysis. A paired-samples t-test, under the 28lb condition, was used to determine the relationship between the mean power of all subjects' dominant versus non-dominant arms. Repeated measures ANOVA was run to then determine differences in mean powers. RESULTS: Power achieved in all movements was similar (r values ranged from 0.723-0.954; p<0.001) at the 28 lb load. On average, an individual's dominant arm during abduction produced less power than the non-dominant arm (143.6 ± 63.5 watts compared to 127.7 ± 50.2; p=0.050). However, external rotation of the dominant arm tended to generate more than non-dominant arms (p=0.053). Correlation values close to 1.00 across all comparisons demonstrated the variance between arms was minimal. The results of the ANOVA showed no statistical differences between arms. CONCLUSIONS: The current assumption that dominant limbs are capable of greater power may not be true in all planes and when tested with isotonic loads applied in three-dimensional space. Our subjects did not demonstrate power imbalances between dominant and non-dominant arms.

190 This study examined the effects of eccentric exercise on blood glutathione status to determine if there was a relationship between delayed onset muscle soreness (DOMS), creatine kinase (CK) and oxidative stress. Eight healthy male subjects (26.5 ± 1.5yrs) performed a single bout of 60 eccentric elbow extensions using their nondominant arm. Blood and muscle soreness parameters were obtained prior to, immediately after, 24, 48, 72 and 96 hrs after the eccentric exercise. Performance measures were compared in both dominant and nondominant arms. No changes in the dominant arm were noted. Maximum isometric force significantly decreased immediately to 96 hrs, range of motion decreased 24-96 hrs, and DOMS increased 24-72 hrs (p<0.02) in the nondominant arm as indicated by repeated measures ANOVA. DOMS peaked at 48 hrs (5.84 ± .93) compared to baseline (1.4 ± .2) and CK peaked at 72 Hrs (1620 ± 500 IU) compared to baseline (140 ± 47). Glutathione in the reduced form (GSH) was not significantly affected but did decrease 23% at 24 hr and continued at this level for 96 hrs. Oxidized glutathione (GSSG) was .16 mM and was fairly stable over time. Total glutathione was .87 mM and fluctuated very little over the times measured (.73-.87 mM). There were no significant correlations between either blood GSH or GSSG and DOMS and CK. The results suggest that eccentric exercise can result in DOMS and CK release into the blood without alterations in glutathione status. These results indicate that DOMS and muscle damage are not related to oxidative stress in the blood as monitored by glutathione status. This does not rule out oxidative stress as a contributory factor to muscle membrane damage.

1. Overarm throws made with the nondominant arm are usually less accurate than those made with the dominant arm. The objective was to determine the errors in the joint rotations associated with this inaccuracy, and thereby to gain insight into the neural mechanisms that contribute to skill in overarm throwing. 2. Overarm throws from both left and right arms were recorded on different occasions as six right-handed subjects sat with a fixed trunk and threw 150 tennis balls at about the same speed at a 6-cm square on a target grid 3 m away. Joint rotations at the shoulder, elbow, wrist, and finger, and arm translations, were computed from recordings of arm segment orientations made with the magnetic-field search-coil technique. 3. All subjects threw less accurately in this task with the left (nondominant) arm. For throws made with the left arm, the height of ball impact on the target grid was related to hand trajectory length and to hand orientation in space at ball release, but not to hand trajectory height. 4. Two hypotheses were proposed to explain the decreased ball accuracy in the high-low direction during throwing with the nondominant arm: that it was caused by increased variability in the velocity or timing of onset of rotations at proximal joints (which determine the path of the hand through space) or increased variability in the velocity or timing of onset of finger extension (which determine the moment of ball release). 5. A prediction of the first hypothesis was that proximal joint rotations should be more variable in throws with the left arm. This was the case for the majority of proximal joint rotations in the six subjects when variability was examined in joint space. However, some proximal joint rotations were more variable in the right arm. 6. The first hypothesis was directly tested by determining whether hand angular position in space (which represents the sum of all proximal joint rotations) was related to ball impact height on the target grid at a fixed translational position in the throw. No relation was found between these variables for throws with the left arm in four subjects, whereas a weak relation was found for two subjects. It was concluded that, considering all subjects, the first hypothesis could not explain the results. 7. In contrast, in agreement with the second hypothesis, a strong relation (P < 0.001) was found in all subjects between ball impact height on the target grid and time of ball release for throws with the left arm, and with time of onset of finger extension. 8. Across all six subjects the timing precision (windows) for 95% of the throws was (for ball release) right arm, 9.3 ms; left arm, 22.5 ms; (for onset of finger extension) right arm, 13.7 ms; left arm, 26.7 ms. 9. Timing of onset of finger extension was no less accurate than timing of onset of other joint rotations for both left and right arms. However, simulations of throws showed that, for the same error in timing, finger extension had twice as large an effect on ball direction as any other joint rotation. Timing errors at the fingers have a greater effect than errors at other joints because finger errors are scaled by the higher angular velocity of the hand in space rather than by the smaller angular velocities of the individual joints. 10. It is concluded that although rotations were in general more variable at both proximal and distal joints of the nondominant (left) arm, the major cause of its decreased throwing accuracy was increased variability at the distal joints, i.e., in the timing of onset of finger extension. This may be due to a lack of precision in the commands from the right hemisphere to the left fingers in right-handed throwers.

Objectives:Musculoskeletal adaptations on the dominant arm of baseball pitchers are typically (1) a gain in glenohumeral external rotation (ER) range of motion (ROM), (2) a loss of glenohumeral internal rotation (IR) ROM, (3) posterior shoulder tightness, (4) weakness in the empty can test, and (5) increased IR strength. The purpose of this study was to determine if these adaptations differed between righthand dominant (RHD) versus lefthand dominant (LHD) pitchers. Based on recent work it was hypothesized that ROM adaptations would be less apparent in LHD pitchers, but strength adaptations would not differ between RHD and LHD pitchers.Methods:Shoulder ROM and strength were measured in 327 baseball pitchers in preseason screening (91 were tested on more than one season, 418 player-seasons, 322 RHD vs. 96 LHD). There were 157 youth pitchers (age 11-15 yr) 146 adolescent pitchers (age 16-17 yr) and 115 adult pitchers (age 18-24 yr). ER ROM, IR ROM and posterior shoulder ROM (Tyler test) were measured with a digital level. Empty can, ER, IR and scapular retraction strength were measured with a hand-held dynamometer. Differences between the dominant and nondominant arms, between RHD and LHD pitchers, and between age groups, were assessed using mixed model analysis of variance (mean and SD reported).Results:ROM Adaptations RHD pitchers had 11±10° more ER ROM on the dominant versus nondominant arm (P<0.001) but LHD pitchers had no ER ROM difference (0±10°, P=0.685). The difference in ER ROM between RHD and LHD pitchers (P<0.001) was unaffected by age (P=0.829).IR ROM loss on the dominant versus nondominant arm for RHD pitchers (10±11°) was greater (P<0.001) than for LHD pitchers (5±10°). This difference was apparent for youth pitchers (RHD 9±9° vs. LHD 1±9°, P<0.001) and adolescent pitchers (RHD 12±10 vs. LHD 5±11°, P<0.001) but not for adult pitchers (RHD 9±14° vs. LHD 8±10°, P=0.863; RHD vs. LHD by Age Group P=0.040).Total ROM (ER+IR ROM) adaptations also differed between RHD and LHD pitchers (P<0.001) and this effect was more apparent in the adult pitchers (Age Group by RHD vs. LHD P=0.027): RHD adult pitchers had a 4±15° gain in total ROM on the dominant side (P=0.007) while LHD adult pitchers had a 7±10° loss in total ROM on the dominant side (P=0.002).Posterior shoulder tightness on the dominant side was affected by arm dominance and age (P=0.038); for youth and adolescent pitchers there was no difference between RHD and LHD pitchers (youth RHD 6±13° vs. LHD 10±11°, P=0.156; adolescent RHD 5±10° vs. LHD 8±15°) but for adult pitchers, posterior shoulder tightness was greater for RHD versus LHD pitchers (6±8° vs. 1±11°, P=0.032).Strength AdaptationsFor the empty can test, RHD pitchers were weaker on the dominant versus nondominant arm (5±15%, P<0.001) while there was no difference between the dominant and nondominant arms for LHD pitchers (3±16% stronger on dominant side P=0.100; RHD vs. LHD P<0.001).For IR strength, RHD pitchers were stronger on the dominant arm (7±17%, P<0.001) while there was no difference between the dominant and nondominant arms for LHD pitchers (2±21% P=0.360; RHD vs. LHD P=0.032).By contrast, for scapular retraction strength, LHD pitchers were stronger on the dominant arm (6±19%, P=0.007) while there was no difference between the dominant and nondominant arms for RHD pitchers (0±15% P=0.723; RHD vs. LHD P=0.003). Dominant versus nondominant ER strength was not different between RHD and LHD pitchers (P=0.323).Conclusions:The typical strength and ROM adaptations seen in baseball pitchers were mostly absent, or diminished, in LHD pitchers, but with some age dependent effects for ROM. Adult RHD pitchers had IR ROM loss and posterior shoulder tightness, but paradoxically adult LHD pitchers had IR ROM loss without associated posterior shoulder. The opposite was the case for youth and adolescent pitchers, with LHD pitchers having posterior shoulder tightness in the absence of IR ROM loss. Differences in strength adaptations between RHD and LHD pitchers have not been reported previously.Epidemiological studies examining the role of strength and ROM in injury risk for baseball pitchers have not previously accounted for differences between lefthanded and righthanded pitchers.

Objective performance indicators during specific steps of robotic right colectomy can differentiate surgeon expertise

Do dominant and non-dominant arms respond similarly to maximal eccentric exercise of the elbow flexors?

Physiology Understanding (PhUn) week is the K‐12 outreach program of the American Physiological Society to enhance STEM education. During a PhUn week activity, we seek to observed differences between boys and girls in the electromyography (EMG) of the biceps brachii. An EMG signal is the electrical manifestations of the neuromuscular activity, or action potential, in response to muscle contractions. The signals wavelengths are recorded as a mean voltage or peak‐to‐peak (PP) time. EMG could be affected by the anatomical and physiological characteristics of the muscle, the nervous system, as well as features of the instrumentation being utilized to analyze them. Seventeen middle school students (7 boys and 10 girls), between the ages of 12–14, were ask to voluntarily participate in PhUn week. A Biopac MP40 system was used to acquire the EMG data by examining motor recruitment and skeletal muscle fatigue. The EMG values were recorded on both dominant and non‐dominant arms while holding a 10lb weight at a 45‐degree elbow flexion, for a duration of 2 seconds. Thereafter the same procedure was performed with a 20lb weight and held until skeletal muscle fatigue was reached. The results showed that, overall, there was significant differences between dominant and non‐dominant arms only in P‐P at 10lb (1.4±2.1 vs. 0.9±1.2 ms, respectively, p&lt;0.05). There were no differences between dominant and non‐dominant arms in any EMG signal in boys or girls. However, there was a significant difference between boys and girls when comparing all the P‐P times for 10 and 20lb in dominant and non‐dominant arms showing a higher muscle fiber recruitment in boys. The evidence suggest that the dominant arm tends to have a higher activation of muscle fibers, as opposed to the non‐dominant, and that more muscle fibers are recruited in boys than girls, when performing the same task.Support or Funding InformationThis work was partially supported by the National Institute of General Medicine Sciences of the National Institute of Health under linked Awards Numbers RL5GM118969, TL4GM118971, and UL1GM118970.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The purpose of this study was to comparatively analyze the active stability of shoulder joints according to the frequency of overhead motions, such as serving and spiking, engaged in by female professional volleyball athletes who play different positions, and to provide the results as the basic data for developing exercise programs to prevent shoulder joint injuries. The subjects of this study were 50 Korean female professional volleyball players and positions were as follows: left and right attackers, centers, setters, and liberos. The external rotation and internal rotation muscle strength and muscle strength ratios of the dominant and non-dominant arms of all subjects were measured using Biodex. The results of this study are as follows: Frist, no significant differences were found in the internal and external rotation muscle strength of the dominant and non-dominant arms between positions. Second, for the shoulder joint muscle strength ratio of the dominant arm, by position, the setter showed significantly greater stability compared to the other positions. Third, for the shoulder joint muscle strength ratio of the non-dominant arm, by position, no significant difference in stability between positions was found. Fourth, it was found that the dominant arm had significantly greater instability of the shoulder joint than the non-dominant arm for attackers and centers, but no significant difference was found for setters and liberos. This study comparatively analyzed the muscle strength ratios of the external/internal rotations and dominant/non-dominant arms, which can determine the stability of the shoulder joints between female professional volleyball playing positions that engage in jumps and spikes using only the dominant hand and positions that do not.

Interlimb differences in reach control could impact the learning of a motor sequence that requires whole-arm movements. The purpose of this study was to investigate the learning of an implicit, 3-dimensional whole-arm sequence task with the non-dominant left arm compared to the dominant right arm. Thirty-one right-hand dominant adults completed two consecutive days of practice of a motor sequence task presented in a virtual environment with either their dominant right or non-dominant left arm. Targets were presented one-at-a-time alternating between Random and Repeated sequences. Task performance was indicated by the time to complete the sequence (response time), and kinematic measures (hand path distance, peak velocity) were used to examine how movements changed over time. While the Left Arm group was slower than the Right Arm group at baseline, both groups significantly improved response time with practice with the Left Arm group demonstrating greater gains. The Left Arm group improved performance by decreasing hand path distance (straighter path to targets) while the Right Arm group improved performance through a smaller decrease in hand path distance combined with increasing peak velocity. Gains made during practice on Day 1 were retained on Day 2 for both groups. Overall, individuals reaching with the non-dominant left arm learned the whole-arm motor sequence task but did so through a different strategy than individuals reaching with the dominant right arm. The strategy adopted for the learning of movement sequences that require whole-arm movements may be impacted by differences in reach control between the nondominant and dominant arms.

Pathologies such as anterior instability and impingement are common in baseball and have been linked to decreases in internal rotation (IR) and concurrent increases in external rotation (ER). In addition, alterations to scapular position have been identified in this population, but the chronology of these adaptations is uncertain. To determine whether there is a change in range of motion and scapular position after a single baseball season. Prospective cohort. High school. 19 high school baseball players (age 16.6 +/- 0.8 y, mass 78.6 +/- 12.0 kg, height 180.3 +/- 6.2 cm). Subjects were measured for all dependent variables at preseason and postseason. Participants were measured for glenohumeral (GH) IR and ER with the scapula stabilized. Total GH range of motion was calculated as the sum of IR and ER. Scapular upward rotation was measured at 0 degrees, 60 degrees, 90 degrees, and 120 degrees of GH abduction in the scapular plane, and scapular protraction, at 0 degrees, hands on hips, and 90 degrees of GH abduction. Overall, the dominant arm had significantly less GH IR (11.4 degrees, P = .005) and significantly more ER (4.7 degrees, P = .001) than the nondominant arm. Total motion in the dominant arm was significantly less than in the nondominant arm (6.7 degrees, P = .001). Scapular upward rotation in the dominant arm significantly increased at 0 degrees (2.4 degrees, P = .002) and significantly decreased at 90 degrees (3.2 degrees, P = .001) and 120 degrees (3.2 degrees, P < .001) of abduction from preseason to postseason. Scapular protraction in the nondominant arm significantly decreased at 45 degrees (0.32 cm, P = .017) and 90 degrees (0.33 cm, P = .006) from preseason to postseason. These data suggest that scapular adaptations may be acquired over a relatively short period (12 wk) in a competitive baseball season. Competitive high school baseball players also presented with significant GH motion differences between their dominant and nondominant arms. Total motion was also significantly less in the dominant arm than in the nondominant arm.

In the present study, we compared the bone mineral content (BMC) and bone mineral density (BMD) in the arms of 11 female volleyball players (mean age 22.0 +/- 2.6 years) training for about 8 hours/week, and 11 nonactive females aged 24.6 +/- 3.1 years (mean +/- SD) not participating in regular or organized sport activity. Using dual X-ray absorptiometry (DXA), BMC was measured in the proximal and distal humerus, and BMD in the distal radius. Isokinetic concentric peak torque (highest value attained during 5 or 10 repetitions) of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow were measured using an isokinetic dynamometer. The volleyball players had significantly higher BMC (P < 0.05) at the proximal humerus of the dominant arm compared with the nonactive group, but there were no differences between the groups in BMC of the distal humerus and BMD of the distal radius. In the volleyball players, BMC was significantly higher at the proximal humerus, at the distal humerus, and at the distal radius in the dominant compared with the nondominant arm. In the nonactive group, there were no significant differences in BMC and BMD between the dominant and nondominant arm at any site measured. Except for shoulder internal rotation strength and elbow flexion strength at 90 degrees/second that was higher in the dominant arm in the volleyball players, there were no significant differences in muscle strength of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow between the dominant and nondominant arm in the volleyball players and nonactive controls. In the volleyball players, but not in the nonactive controls, there were several significant relationships between shoulder and elbow strength and BMC at the distal humerus of the dominant and especially the nondominant arm. These results show that young female volleyball players have a higher bone mass in the proximal humerus, distal humerus, and distal radius in the dominant compared with the nondominant arm, and a higher bone mass in the proximal humerus compared with nonactive controls. Muscle strength of the rotator muscles of the shoulder is not related to the higher bone mass in the proximal humerus of the dominant arm. Theoretically, the observed differences in bone mass can be related to the type of loading the skeleton undergoes when playing volleyball.

We tested the hypothesis that dominant and nondominant overarm throws of different speeds are made by time-scaling of joint rotations, i.e., by joint rotations that have the same positions and amplitudes but that are scaled in time. Eight skilled subjects stood and made overarm throws with both their dominant and nondominant arms. Six joint rotations were computed from recordings of arm segments made with the search-coil technique. Throws made with nondominant arms were less accurate and had lower ball speeds. In contrast to the hypothesis, dominant arms showed large and consistent differences between fast and slow throws in six-dimensional angular position joint space. These same throws showed similar hand angular paths when these were time-scaled based on ball speed. Nondominant arms showed only small differences in angular position joint space in fast and slow throws. It is concluded that a joint space pattern resembling that predicted by time-scaling occurs in nondominant arm throwing when it is unskilled. However, time-scaling does not occur in dominant arm throwing, i.e., a skilled fast throw is not simply a skilled slow throw whose joint positions and amplitudes remain constant but whose joint velocities are sped-up. We hypothesize for future study that, when subjects first learn to throw at different speeds with their dominant arms, they use time-scaling of joint rotations that involves compensating for interaction torques; then as they become skilled at throwing fast, time-scaling is superseded by a more complex pattern of interjoint coordination that involves exploiting interaction torques.

Introduction: The purpose of this study was to investigate the Range of Motion (ROM) and balance symmetry between dominant and non-dominant arms in classic female wrestlers. Materials and Methods: In this cross-sectional study, 13 members of the Iranian Women’s National Classic Wrestling Team participated voluntarily. The shoulder ROM was measured by a goniometer and dynamic balance was assessed by the Y-balance test. Data analysis was done by running a paired t-test, with a 0.95 confidence level (α&lt;0.05). Results: There was no significant difference between dominant and non-dominant upper extremities in flexion (P=0.162), extension (P=0.264), abduction (P=0.077), internal rotation (P=0.972), and external rotation (0.945). A significant difference was found in the Y-balance test in medial (P=0.026) and inferior-lateral directions (P=0.047), but no significant difference in superior-lateral direction (P=0.715) and composite score (P=0.071). Conclusion: Based on the results, it seems that the balance in the dominant arm is better than that in non-dominant arm in the athletes so the non-dominant arm may be at more risk for injury development. We, therefore, recommend that the coaches and trainers pay particular attention to these findings in designing the injury prevention programs.

The purpose of this study was to develop further normative data for an isokinetic profile for intercollegiate baseball pitchers at 180, 300, and 450 degrees.s-1. Information on isokinetic performance at 450 degrees.s-1 was not found in previously published literature. Sixteen intercollegiate baseball pitchers volunteered for isokinetic strength testing of internal and external rotators of the shoulder. The testing was conducted at 180, 300, and 450 degrees.s-1; with the pitchers in a position of function (90 degrees/90 degrees). The subjects were able to reach maximal velocity for each of the speeds tested, including 450 degrees.s-1. These pitchers demonstrated no significant difference between dominant and nondominant arms for peak torque, torque/body weight, work/body weight, or average power (P < 0.05). Torque produced at 0.2 s was significantly greater in the dominant arm compared with the nondominant arm at 450 degrees.s-1 only. Internal rotation values were significantly greater than external rotation values for all areas of comparison. External rotation/internal rotation ratios remained consistent for each speed tested (approximately 0.65). There is minimal difference in strength values between dominant and nondominant arms of intercollegiate baseball pitchers, with the exception of significantly greater internal rotation peak torque at 0.2 s at 450 degrees.s-1 in the dominant arm. Dominant arm, as well as nondominant arm, ER/IR ratios remain consistent throughout the velocity spectrum. A valid test speed for intercollegiate baseball pitchers appears to be 450 degrees.s-1 when tested before the start of throwing from the pitcher's mound.