Effects of Ankle Position While Performing One- and Two-Leg Floor Bridging Exercises on Core and Lower Extremity Muscle Recruitment.

Given there are no known studies which have examined multiple lower extremity muscles between different ankle positions during bridging activities, the objective was to assess how employing two different ankle positions (PF versus DF) while performing five common bridging exercises (three bipedal and two unipedal) used in rehabilitation and athletic performance affect core and select lower extremity muscle EMG recruitment. Twenty healthy subjects performed a 5 s isometric hold during five two- and one-leg bridge exercises: (1) on right leg with left knee to chest (1LB-LFlex); (2) on right leg with left knee extended (1LB-LExt); (3) standard two-leg bridge (2LB); (4) two-leg bridge with resistance band around knees (2LB-ABD); and (5) two-leg bridge with ball between knees (2LB-ADD). Surface electromyographic (EMG) data were collected using a Noraxon Telemyo Direct Transmission System from fourteen muscles: (1) three superficial quadriceps (VM, VL, and RF); (2) three hip abductors (TFL, GMED, and GMAX); (3) medial hamstrings (ST) and lateral hamstrings (BF); (4) hip adductors (ADD); (5) erector spinae (ES); (6) latissimus dorsi (LATS); (7) upper rectus abdominis (RA); and (8) external oblique (EO) and internal oblique (IO). EMG data were normalized by maximum voluntary isometric contractions (MVICs). A paired t-test (p < 0.01) was used to assess differences in normalized mean EMG activities between DF and PF for each exercise. EMG activities were significantly greater in DF than PF for the (a) VM, VL, and RF during 1LB-LFlex; (b) ADD during 1LB-LFlex, 1LB-LExt; (c) EO during 1LB-LFlex; and (d) IO during 1LB-LFex. In contrast, EMG activities were significantly greater in PF than DF for ST and BF during all five bridge exercises. Bridging with PF (feet flat) was most effective in recruiting the hamstrings, while bridging with DF (feet up) was most effective in recruiting the quadriceps, hip adductors, and internal and external obliques.

Induced power analysis of sequential body motion and elbow valgus load during baseball pitching.

The flow of mechanical energy of segmental motion during baseball pitching is poorly understood, particularly in relation to the valgus torque at the elbow which is prone to pitching-related injuries. This study employed an induced power analysis to determine the components of muscle and velocity-dependent torques that contribute to the power of throwing arm segments when the elbow is under valgus load during the arm-cocking phase of pitching. The 3D throwing kinematics and kinetics of 10 adult pitchers were included in this analysis. Pitchers threw with a maximum elbow valgus torque of 73 ± 20 N•m. The trunk flexion and rotation components of the velocity-dependent torque were the greatest contributors to the work of the forearm at -0.53 ± 0.22 J/kg and -0.43 ± 0.21 J/kg, respectively. Approximately 86% of the total energy transferred through the elbow by the velocity-dependent torque was due to trunk motion, which appears to drive the power of accelerating the throwing elbow in valgus. These results support the importance of trunk motion as a key component in the development of elbow torque and ball velocity. Therefore, this study has practical implications for baseball pitchers seeking to minimise injury risk while improving performance.

Inverse dynamics analysis of youth pitching arm kinetics using body composition imaging.

This study's objectives were to: (1) assess whether dual energy X-ray absorptiometry (DXA)-mass inverse dynamics (ID) alters predictions of youth pitching arm kinetics and (2) investigate correlations between kinetics and body composition. Eighteen 10- to 11-year-olds pitched 10 fastballs. DXA scans were conducted to obtain participant-specific upper arm, forearm, and hand masses. Pitching arm segment masses and kinetics calculated with scaled and DXA masses were compared with paired t-tests and correlations were investigated with linear regression. Hand (p < 0.001) and upper arm (p < 0.001) DXA masses were greater, while forearm (p < 0.001) DXA masses were lesser, than their scaled masses. Shoulder compressive force (p < 0.001), internal rotation torque (p < 0.001), and horizontal adduction torque (p = 0.002) increased when using DXA masses. Shoulder compressive force correlated with body mass (p < 0.001) and body mass index (BMI; p = 0.002) and elbow varus torque correlated with body mass (p < 0.05). The main conclusions were that (1) using participant-specific mass ratios leads to different predictions of injury-related pitching arm kinetics and, thus, may improve our understanding of injury risk factors; and (2) pitching arm kinetics were correlated with body composition measures and a relatively high total body mass and/or BMI may increase shoulder and/or elbow injury risk.

Relationship between ground reaction force and throwing arm kinetics in high school and collegiate pitchers.

BACKGROUND: Throwing a baseball requires the transmission of forces generated in the lower extremity, through the trunk, to the upper extremity, and ultimately translates to the ball. A disruption in the functioning of the lower extremities could lead to altered upper extremity kinematics and increased load exerted on the shoulder and elbow. The purpose of this study was to examine the relationship of ground reaction forces (GRF) on the drive and stride sides and kinetics of the throwing arm in high school and collegiate baseball pitchers. METHODS: In this retrospective cross-sectional study, data that were previously collected during a pitching evaluation were analyzed. Fifty high school pitchers and 26 collegiate pitchers had received a pitching evaluation. Multiple regression analysis was used to examine the relationships between variables. RESULTS: Only the drive leg medial force was determined to be a significant predictor of maximum shoulder external rotation torque. Maximum elbow valgus torque was not correlated with any GRF variables and ball speed was only weakly correlated with stride leg medial force. There were no significant differences in GRFs between the high school and college pitchers. CONCLUSIONS: Due to the limited relationships present, other factors such as muscle strength, coordination, kinematics, or stride technique may overshadow the effects of GRF in highly skilled pitchers and warrant further investigation. Understanding this relationship will be important to both enhancing performance and avoiding injury.

Physiological Performance Measures as Indicators of CrossFit® Performance.

CrossFit® began as another exercise program to improve physical fitness and has rapidly grown into the "sport of fitness". However, little is understood as to the physiological indicators that determine CrossFit® sport performance. The purpose of this study was to determine which physiological performance measure was the greatest indicator of CrossFit® workout performance. Male (n = 12) and female (n = 5) participants successfully completed a treadmill graded exercise test to measure maximal oxygen uptake (VO2max), a 3-minute all-out running test (3MT) to determine critical speed (CS) and the finite capacity for running speeds above CS (D'), a Wingate anaerobic test (WAnT) to assess anaerobic peak and mean power, the CrossFit® total to measure total body strength, as well as the CrossFit® benchmark workouts: Fran, Grace, and Nancy. It was hypothesized that CS and total body strength would be the greatest indicators of CrossFit® performance. Pearson's r correlations were used to determine the relationship of benchmark performance data and the physiological performance measures. For each benchmark-dependent variable, a stepwise linear regression was created using significant correlative data. For the workout Fran, back squat strength explained 42% of the variance. VO2max explained 68% of the variance for the workout Nancy. Lastly, anaerobic peak power explained 57% of the variance for performance on the CrossFit® total. In conclusion, results demonstrated select physiological performance variables may be used to predict CrossFit® workout performance.

Effects of Game Pitch Count and Body Mass Index on Pitching Biomechanics in 9- to 10-Year-Old Baseball Athletes.

BACKGROUND: Pitching while fatigued and body composition may increase the injury risk in youth and adult pitchers. However, the relationships between game pitch count, biomechanics, and body composition have not been reported for a study group restricted to 9- to 10-year-old athletes. HYPOTHESIS: During a simulated game with 9- to 10-year-old athletes, (1) participants will experience biomechanical signs of fatigue, and (2) shoulder and elbow kinetics will correlate with body mass index (BMI). STUDY DESIGN: Descriptive laboratory study. METHODS: Thirteen 9- to 10-year-old youth baseball players pitched a simulated game (75 pitches). Range of motion and muscular output tests were conducted before and after the simulated game to quantify fatigue. Kinematic parameters at foot contact, maximum external rotation, and maximum internal rotation velocity (MIRV), as well as maximum shoulder and elbow kinetics between foot contact and MIRV were compared at pitches 1-5, 34-38, and 71-75. Multivariate analyses of variance were used to test the first hypothesis, and linear regressions were used to test the second hypothesis. RESULTS: MIRV increased from pitches 1-5 to 71-75 (P = .007), and head flexion at MIRV decreased from pitches 1-5 to 34-38 (P = .022). Maximum shoulder horizontal adduction, external rotation, and internal rotation torques increased from pitches 34-38 to 71-75 (P = .031, .023, and .021, respectively). Shoulder compression force increased from pitches 1-5 to 71-75 (P = .011). Correlations of joint torque/force with BMI were found at every pitch period: for example, shoulder internal rotation (R2 = 0.93, P < .001) and elbow varus (R2 = 0.57, P = .003) torques at pitches 1-5. CONCLUSION: Several results differed from those of previous studies with adult pitchers: (1) pitch speed remained steady, (2) shoulder MIRV increased, and (3) shoulder kinetics increased during a simulated game. The strong correlations between joint kinetics and BMI reinforce previous findings that select body composition measures may be correlated with pitching arm joint kinetics for youth baseball pitchers. CLINICAL RELEVANCE: The results improve our understanding of pitching biomechanics for 9- to 10-year-old baseball pitchers and may be used in future studies to improve evidence-based injury prevention guidelines.

Correlation of throwing mechanics with elbow valgus load in adult baseball pitchers.

BACKGROUND: Studies have shown that various biomechanical factors affect valgus extension overload during baseball pitching; yet, their relationships are not clearly defined, and factors such as trunk rotation and arm slot have not been investigated. HYPOTHESIS: The onset of trunk rotation, with other biomechanical variables that define sequential body motion, will significantly predict elbow valgus loading. STUDY DESIGN: Descriptive laboratory study. METHODS: Sixty-nine adult baseball players pitched off an indoor mound during 3-dimensional motion analysis to measure whole body kinematics and kinetics at 240 Hz. Thirteen biomechanical variables were calculated and extracted for regression analysis to investigate their associations with elbow valgus load. A 2-way analysis of variance compared valgus torques between pitchers with 2 onsets of trunk rotation (before and after front-foot contact) and 2 arm slot positions (overhand and sidearm). RESULTS: Six biomechanical variables had significant correlations (P < .02) with elbow valgus torque-with maximum shoulder external rotation, elbow flexion at peak valgus torque, and elbow valgus loading rate accounting for 68% of its variance. Reduced elbow valgus torques were associated with increased elbow flexion (P < .01). Players who initiated trunk rotation before front-foot contact had significantly higher elbow valgus torques than did those who rotated afterward (P = .02). Fourteen pitchers displayed a sidearm delivery and had significantly higher elbow valgus torques than did those with an overhand arm slot position. CONCLUSION: Valgus torque at the elbow during baseball pitching is associated with 6 biomechanical variables of sequential body motion. A condition of late trunk rotation, reduced shoulder external rotation, and increased elbow flexion appeared to be most closely related to valgus torque. Sidearm pitchers appeared to be more susceptible than overhand pitchers to reduced elbow valgus torque. CLINICAL RELEVANCE: The biomechanical findings of this study offer scientific feedback for developing methods used to minimize the effects of valgus load on pitching-related elbow injuries.

Effects of upper trunk rotation on shoulder joint torque among baseball pitchers of various levels.

High rotational torques during baseball pitching are believed to be linked to most overuse injuries at the shoulder. This study investigated the effects of trunk rotation on shoulder rotational torques during pitching. A total of 38 pitchers from the professional, college, high school, and youth ranks were recruited for motion analysis. Professional pitchers demonstrated the least amount of rotational torque (p = .001) among skeletally mature players, while exhibiting the ability to rotate their trunks significantly later in the pitching cycle, as compared to other groups (p = .01). It was concluded that the timing of their rotation was optimized as to allow the throwing shoulder to move with decreased joint loading by conserving the momentum generated by the trunk. These results suggest that a specific pattern in throwing can be utilized to increase the efficiency of the pitch, which would allow a player to improve performance with decreased risk of overuse injury.