Wendi H. Weimar

Gluteus medius and scapula muscle activations in youth baseball pitchers.

Abstract Oliver, GD, Weimar, WH, and Plummer, HA. Gluteus medius and scapula muscle activations in youth baseball pitchers. J Strength Cond Res 29(6): 1494–1499, 2015—The baseball pitching motion is a total kinetic chain activity that must efficiently use both the upper and lower extremity. Of particular importance is the scapular motion, which is critical for humeral positioning and proper alignment of shoulder musculature. It was hypothesized that scapular stability is enhanced by pelvic girdle stability. Therefore, it was the purpose of this study to determine the muscle activations of selected pelvic and scapular stabilizing muscles during a fastball pitch in youth baseball pitchers. Twenty youth baseball pitchers (age: 11.3 + 1.0 years; height: 152.4 + 9.0 cm; weight: 47.5 + 11.3 kg) were recorded throwing 4-seam fastballs for strikes. Data revealed moderate (20–39% maximum voluntary isometric contraction [MVIC]) to moderately strong (>40% MVIC) activation of the ipsilateral (throwing arm side) gluteus medius, upper trapezius, and serratus anterior throughout phases 2 (maximum shoulder external rotation to ball release) and 3 (ball release to maximum shoulder internal rotation). Moderately strong activation (>40% MVIC) of the upper trapezius and serratus anterior was noted during phases 2 and 3 of the pitching motion. Pearsons product-moment correlation revealed significant relationships between bilateral gluteus medius and the force couples about the scapula during all 3 phases of the pitching motion. The results of this study provide important data that improve the understanding of the muscular relationship between the pelvic and scapular stabilizers during the fastball pitch. Training and rehabilitation programs should consider focusing on lumbopelvic-hip and scapular muscle strengthening as well as coordinated strengthening of the pelvic and scapular stabilizers, in baseball pitchers.

Hip range of motion and scapula position in youth baseball pitching pre and post simulated game.

Abstract Lower to upper extremity sequencing of energy and force is linked by virtue of the scapula. It was the purpose of this study to examine the relationship between passive hip rotational range of motion and scapular kinematics during baseball pitching. Nineteen youth baseball players (11.3 ± 0.6 years; 151.8 ± 8.8 cm; 45.9 ± 10.9 kg) with no history of injury participated. Bilateral hip passive rotational range of motion was measured pre and post pitching a simulated game. Scapular kinematics at the position of shoulder maximum external rotation during the pitching cycle were recorded in the first and last innings of the simulated game. Post simulated game, stance leg hip passive internal rotation revealed significant correlations (r = −0.57, P = 0.01) with scapula anterior/posterior tilt at the pitching event of maximum humeral external rotation. The current study reveals that pitching a simulated game results in alterations throughout the kinetic chain. Specifically, this study strengthens the notion that lumbopelvic-hip complex parameters play a significant role in shoulder motion. With this link identified, it is suggested that clinical focus be directed musculature about the lumbopelvic-hip complex as well as muscles that work to stabilise the scapula during dynamic movement.

Effects of a Simulated Game on Muscle Activation in Youth Baseball Pitchers

Abstract Oliver, GD, Weimar, WH, and Henning, LE. Effects of a simulated game on muscle activation in youth baseball pitchers. J Strength Cond Res 30(2): 415–420, 2016—It is generally accepted that playing with fatigue is a primary predictor of injury in youth baseball because muscular fatigue is believed to alter mechanics during the arm cocking and acceleration phases. Therefore, the purpose of this study was to quantitatively describe gluteal and upper extremity muscle activations in youth baseball pitchers during a simulated game. Twenty-three youth baseball players (11.2 ± 0.8 years; 151.4 ± 8.7 cm; 47.5 ± 10.8 kg) participated. Data were collected through a Delsys Bagnoli–8-channel electromyography system. Single differential electrodes (interelectrode distance: 10 mm) were attached to the bilateral gluteus maximus and medius and throwing side latissimus dorsi, lower trapezius, and serratus anterior and upper trapezius. After warm-up, participants were instructed to throw randomly provided game situations over a regulation distance (46 feet; 14.02 meters) to a catcher. Three, 4-seam fastballs for strikes, thrown in the first and last innings of the simulated game were selected for analysis. A multivariate analysis of variance revealed no statistically significant differences in muscle activity at the 3 phases of the throw, between first and last innings of the simulated game with an observed power of 0.274 (phase 1: foot contact to maximum shoulder external rotation), 0.297 (phase 2: maximum shoulder external rotation to ball release), and 0.226 (phase 3: ball release to maximum shoulder internal rotation). Examining muscle activations as a pitcher approaches fatigue provides information on how long a pitcher can perform before mechanical alterations occur. Although this study did not reveal significant changes, it did reiterate the fact that pitch counts may be working in possibly preventing a youth pitcher throwing to fatigue.

Scapula Kinematics of Youth Baseball Players.

Abstract Literature has revealed the importance of quantifying resting scapular posture in overhead athletes as well as quantifying scapular kinematics during dynamic movement. Prior to this project much of the attention in throwing research had been focused on the position of the humerus without description of the positioning of the scapula. Therefore, it was the purpose of this study to present scapular kinematics during pitching in youth baseball players. Twenty-five youth baseball players (age 11.3 + 1.0 years; body height 152.4 + 9.0 cm; body mass 47.5 + 11.3 kg), with no history of injury, participated in the study. Scapular kinematics at the events of maximum humeral external rotation (MER) and maximum humeral internal rotation (MIR) during the pitching motion were assessed three-dimensionally while pitching fastballs for strikes. Results revealed that at the event of MER, the scapula was in a position of retraction, upward rotation and a posterior tilt. While at the event of MIR, the scapula was protracted, upward rotated and tilted anteriorly.

Hip and Shoulder Range of Motion in Youth Baseball Pitchers

Abstract Oliver, GD and Weimar, WH. Hip and shoulder range of motion in youth baseball pitchers. J Strength Cond Res 30(10): 2823–2827, 2016—Lack of range of motion (ROM) has long been suspected as contributing to injury in baseball pitchers. However, all previous ROM research has focused on collegiate and professional pitchers. It was thus the purpose of this study to measure and evaluate bilateral hip and throwing shoulder rotational passive range of motion (PROM) in youth baseball pitchers. Twenty-six youth baseball pitchers (11.3 ± 1.0 years; 152.4 ± 9.0 cm; 47.5 ± 11.3 kg) with no history of injury participated. Bilateral hip and throwing shoulder rotational PROM was measured. There were no significant side-to-side differences for the hip variables (p ≥ 0.05). Shoulder external rotation (ER) was significantly greater than shoulder internal rotation (IR). And the lead leg hip had significantly greater ER than IR. Shoulder ER revealed significant correlations with both lead and stance hip IR (r = 0.45, p = 0.02 and r = 0.48, p = 0.01, respectively). The youth baseball pitchers in this study displayed similar PROM patterns as collegiate and professional baseball pitchers. Additionally, our youth baseball pitchers also presented strong relationships between hip and shoulder PROM. This study reveals that the PROM patterns displayed by these youth may indicate that their available ROM could survive maturation. It is therefore suggested that clinical focus be directed to maintaining hip and shoulder rotational ROM throughout maturation in attempt to determine a possible relations between injurious mechanisms and performance enhancement.

Biomechanical comparison of frontal plane knee joint moment arms during normal and Tai Chi walking.

[Purpose] Medial knee osteoarthritis, a degenerative joint disease, affects adults. The external knee adduction moment, a surrogate knee-loading measure, has clinical implications for knee osteoarthritis patients. Tai Chi is a promising intervention for pain alleviation in knee osteoarthritis; however, the characteristics of external knee adduction moment during Tai Chi have not been established. [Subjects and Methods] During normal and Tai Chi walking, a gait analysis was performed to compare the external knee adduction moment moment-arm characteristics and paired t-tests to compare moment-arm magnitudes. [Results] A significant difference was observed in the average lateral direction of moment-arm magnitude during Tai Chi walking (−0.0239 ± 0.011 m) compared to that during normal walking (−0.0057 ± 0.004 m). No significant difference was found between conditions in average medial direction of moment-arm magnitude (normal walking: 0.0143 ± 0.010 m; Tai Chi walking: 0.0098 ± 0.014 m). [Conclusion] Tai Chi walking produced a larger peak lateral moment-arm value than normal walking during the stance phase, whereas Tai Chi walking and normal walking peak medial moment-arm values were similar, suggesting that medial knee joint loading may be avoided during Tai Chi walking.

Footwear effects on lower extremity coordination

It was expected that the flexible upper would allow a more homogeneous pressure distribution due to a more gradual foot rollover process during running. However, the peak pressure was higher in the minimalistic upper and the contact time was lower even with the same controlled velocity. Hagen and Hennig (2009) found that using higher and tighter shoe lacing, and thus a more adjusted and firmer link between the shoe and the entire foot, produced lower peak pressures in the rearfoot and lower loading rates. The authors attributed their findings to a better coupling between foot-shoe, thus facilitating the use of the impact absorbing technology of the footwear and other mechanical properties of the shoe. Our results can also be explained by a more adjusted and firmer contact within a shoe by the structured upper and then the runner could homogeneously distribute the pressure over the entire foot, reducing the plantar loads. We can conclude that to maximize the use of outsoles technologies, it is important that the upper, even when minimalistic, have to have a good fit with the foot anthropometry.

Dual-task effects on lower extremity gait coordination during barefoot & shod walking

Past research has indicated significant footwear effects on spatiotemporal and discrete gait variables during gait; however, the level of tactile feedback has also been shown to be an important modulator of gait patterns. The present study aimed to investigate changes in coordination of lower extremity gait coordination during normal shod and barefoot walking, as well as during a simple attention diverting task (matching a metronome during walking). Fifteen (10 female, five male) healthy participants walked on an instrumented walkway during six conditions. Lower extremity kinematic data were collected and continuous relative phase values were calculated for two adjacent joints to determine inter‐segmental coordination. Results indicate that participants exhibited significantly longer strides (P ≤ 0.04) when shod as opposed to barefoot. Participants also displayed greater thigh‐shank coordination variability during the shod, fixed cadence conditions. The present study suggests that individuals will display greater lower extremity coordination variability during dual‐task conditions when shod as opposed to barefoot.

Ex-Vivo Evaluation of a Modified Teno Fix® Device Repair Pattern Versus a 3-Loop Pulley for Repair of Equine Flexor Tendons

OBJECTIVE To compare the load to ultimate failure, load to a 2 mm gap, mode of failure, and gap at failure (mm) of the Teno Fix(®) (TF) to the 3-loop pulley (3LP) for repair of equine tendon lacerations. The use of 4TF devices versus 5TF devices on load to ultimate failure and load to a 2 mm gap was also compared. STUDY DESIGN Ex vivo biomechanical study; unbalanced incomplete block (horse) design. SAMPLES Cadaveric equine forelimb superficial digital flexor tendon (n = 20 paired tendons). METHODS Ten tendon pairs were selected randomly and repaired with a 3LP and 4TF pattern, and 10 tendon pairs repaired with a 3LP and 5TF pattern. Load to ultimate failure, load to a 2 mm gap, mode of failure, and gap at failure were obtained using materials testing. RESULTS The 3LP had a significantly greater ultimate load to failure (P < .001, respectively) and a significantly higher load to a 2 mm gap than both TF repairs (P < .001, respectively). The most frequent mode of failure was suture pull-out for the 3LP and anchor pull-out for the TF. Gap at failure was significantly larger in the 3LP than both TF repairs (P < .001). The ultimate load to failure was significantly higher for the 5TF than the 4TF (P = .004) but there was no significant difference in load to a 2 mm gap, or gap at failure between both TF repairs (P = .11, P = .15, respectively). CONCLUSIONS Neither TF repair was stronger than the 3LP in load to ultimate failure and load to a 2 mm gap. Addition of a fifth TF device significantly increased the load to ultimate failure but did effect the load to a 2 mm gap over the 4TF.