Ralph Escamilla

It is unknown how pitching biomechanics in college baseball pitchers differ between windup and stretch pitching deliveries from a dirt surface mound. The purpose was to assess differences in shoulder and elbow kinetics and pitching kinematics in college pitchers between windup and stretch pitching deliveries from a dirt surface mound. Eighteen college pitchers pitched from a dirt surface mound using windup and stretch pitching deliveries. All pitchers were tested using a 240-Hz, 12-camera motion analysis system, and 28 kinematic and 7 kinetic parameters were calculated. Paired within-subjects t tests (P < .05) were used to assess biomechanical differences between windup and stretch deliveries. Maximum shoulder horizontal adduction torque, maximum shoulder anterior force, maximum lead knee height, ball velocity at ball release, forward trunk tilt at ball release, maximum upper trunk angular velocity, maximum elbow extension angular velocity, and maximum shoulder internal rotation angular velocity were all significantly greater using a windup delivery compared with a stretch delivery. Pelvic drift at maximum lead knee height was the only parameter that was significantly greater in a stretch delivery compared with a windup delivery. Nine of the 35 (26%) biomechanical parameters were significantly different between windup and stretch deliveries. Shoulder injury risk may be slightly lower using a stretch delivery compared with a windup delivery due to overall lower shoulder kinetics during the stretch delivery.

Background While one-legged and two-legged bodyweight squats on unstable and stable surfaces are commonly used during patellofemoral rehabilitation, patellofemoral loading during these exercises is unknown. Understanding how patellofemoral force and stress magnitudes affects different squat variations will aid clinicians in determining how and when to prescribe and progress these squatting types of exercises in patients with patellofemoral pain. Hypothesis/Purpose To quantify patellofemoral force and stress between two squat type variations (BOSU squat versus floor squat) and between two leg variations (one-legged squat versus two-legged squat). It was hypothesized that patellofemoral force and stress would be greater in BOSU squat than floor-squat, and greater in one-legged squat than two-legged squat. Study Design Controlled laboratory biomechanical, repeated-measures, counterbalanced design. Methods Sixteen healthy participants performed one-legged and two-legged BOSU and floor squats. Kinematic and ground-reaction force data were used to calculate resultant knee force and torque using inverse-dynamics, with electromyographic data employed in a knee muscle model to predict resultant knee force and torque at every 10 degrees between 10 degrees-100 degrees knee-angles during the squat-descent and squat-ascent. Repeated-measures 2-way ANOVA (p < 0.01) was employed for statistical analyses. Results Collapsed across one-legged and two-legged conditions, patellofemoral joint force and stress were significantly greater during floor squats than BOSU squats at 40 degrees, 50 degrees, and 70 degrees knee-angles during squat descent and 60 degrees and 50 degrees knee-angles during squat ascent. Collapsed across BOSU and floor squats, patellofemoral joint force and stress were significantly greater for one-legged squats than two-legged squats at all knee-angles. Significant interactions between squat types and leg conditions were found at 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 100 degrees knee-angles during squat-descent, and 100 degrees, 90 degrees, 80 degrees, and 70 degrees knee-angles during squat-ascent, with patellofemoral joint force and stress significantly greater in two-legged floor-squat than two-legged BOSU squat, but no significant differences between one-legged floor-squat and one-legged BOSU squat. Conclusions Squatting progression employing lower to higher patellofemoral loading over time during PFP rehabilitation may be considered: 1) two-legged BOSU squats at lower knee angles (0 degrees- 50 degrees); 2) two-legged floor squats at lower knee angles (0 degrees- 50 degrees); 3) one-legged BOSU and floor squats at lower knee angles (0 degrees- 50 degrees); 4) two-legged BOSU squats at lower and higher knee angles (0 degrees- 100 degrees); 5) two-legged floor squats at lower and higher knee angles (0 degrees- 100 degrees); 6) one-legged BOSU and floor squats at lower and higher knee angles (0 degrees- 100 degrees). Level of Evidence 2

[Purpose] Compare four quick (approximately 60 s), reliable methods of assessing %body-fat (%BF) among young (Y, 18–34 years), middle-age (M, 35–59 years), and older (O, 60–88 years) healthy-adults. [Participants and Methods] One-hundred-eighty healthy males-and-females were equally (n=30) divided into Y, M, and O age groups to assess %BF. The %BF methods were: 1) Bioelectrical-impedance-Inbody770 (IB)–criterion reference; 2) Body-mass-index (BMI); 3) Abdominal-and-hip circumferences (CIR); and 4) Skinfold (SF). [Results] %BF were significantly different among the four body-fat methods and among the three age-groups for both males-and-females. %BF among IB,BMI,CIR, and SF were, respectively, 15.7 ± 4.7%, 19.6 ± 3.2%, 17.3 ± 3.5%, and 12.1 ± 4.1% for Y-males; 18.3 ± 5.7%, 22.8 ± 3.6%, 19.6 ± 3.6%, and 15.6 ± 4.5% for M-males; 24.4 ± 6.5%, 25.8 ± 3.3%, 24.0 ± 4.5%, and 20.0 ± 4.1% for O-males; 24.9 ± 6.9%, 28.9 ± 4.1%, 29.4 ± 4.6%, and 22.4 ± 6.3% for Y-females; 25.1 ± 7.0%, 31.4 ± 4.7%, 33.0 ± 4.5%, and 25.0 ± 4.5% for M-females; 35.1 ± 6.3%, 35.5 ± 4.3%, 38.4 ± 4.8%, and 26.4 ± 3.7% for O-females. [Conclusion]The most accurate %BF-methods to use in clinical settings are CIR for Y-and-M-males, CIR and BMI for O-males, SF for Y-and M-females, and BMI for O-females. The least accurate %BF methods are BMI and SF for Y-males, BMI for M-males, SF for O-males, BMI and CIR for Y-and M-females, and SF for O-females. While all 4-methods of assessing %BF can easily and quickly be employed in clinical settings, some methods significantly underestimate or overestimate %BF and yield different results among varying age groups and sex. These findings help identify people at early health risk of cardiometabolic disease, with O-males and O-females at higher risk.

While bodyweight wall and ball squats are commonly used during patellofemoral rehabilitation, patellofemoral loading while performing these exercises is unknown, which makes it difficult for clinicians to know how to use these exercises in progressing a patient with patellofemoral pathology. Therefore, the purpose was to quantify patellofemoral force and stress between two bodyweight squat variations (ball squat-versus-wall-squat) and between two heel-to-wall-distance (HTWD) variations (long-HTWD versus short-HTWD). Sixteen participants performed a dynamic ball squat and wall squat with long HTWD and short HTWD. Ground reaction force and kinematic data were used to measure resultant knee force and torque from inverse dynamics, while electromyographic data were used in a knee muscle model to predicted resultant knee force and torque, and subsequently all these data were inputted into a biomechanical computer optimization model in order to output patellofemoral joint force and stress at select knee angles. A repeated measures 2-way and 3-way ANOVA (p < 0.01) was employed for statistical analyses. Collapsed across long-HTWD and short-HTWD, patellofemoral joint force and stress were greater in ball squat than wall squat at 30° (p = 0.009), 40° (p = 0.008), 90° (p = 0.003), and 100° (p = 0.005) knee angle during the squat descent, and greater in wall squat than ball squat at 100° (p < 0.001), 90° (p < 0.001), 80° (p = 0.004), and 70° (p = 0.009) knee angle during squat ascent. Collapsed across ball & wall squats, patellofemoral joint force & stress were greater with a short HTWD than a long HTWD at 100° (p = 0.007) and 90° (p = 0.008) knee angle during squat ascent. Patellofemoral joint loading changed according to both squat type and HTWD variations. These differences occurred in part due to differences in forces the wall or ball exerted on the trunk, including friction forces. Overall, patellofemoral force and stress were greater performing the bodyweight wall squat compared to the bodyweight ball squat. Moreover, squatting with short-HTWD produced anterior knee displacement beyond the toes at higher knee angles, resulting in greater patellofemoral force and stress compared to squatting with long-HTWD.

Baseball pitchers employ various contralateral trunk tilt (CTT) positions when pitching depending on if they have an overhand, three-quarter, or sidearm delivery. There are no known studies that have examined how pitching biomechanics are significantly different in professional pitchers with varying amounts of CTT, which may provide insight into shoulder and elbow injury risk among pitchers with different CTT. To assess differences in shoulder and elbow forces and torques and baseball pitching biomechanics in professional pitchers with maximum 30° to 40° CTT (MaxCTT), moderate 15° to 25° CTT (ModCTT), and minimum 0° to 10° CTT (MinCTT). Controlled laboratory study. In total, 215 pitchers were examined, including 46 pitchers with MaxCTT, 126 pitchers with ModCTT, and 43 pitchers with MinCTT. All pitchers were tested using a 240-Hz, 10-camera motion analysis system, and 37 kinematic and kinetic parameters were calculated. Differences in kinematic and kinetic variables among the 3 CTT groups were assessed with a 1-way analysis of variance ( < .01). Maximum shoulder anterior force and maximum elbow proximal force were significantly greater in ModCTT (403 ± 79 N) than MaxCTT (369 ± 75 N) and MinCTT (364 ± 70 N), while maximum elbow flexion torque and shoulder proximal force, respectively, were significantly greater in ModCTT (69 ± 11 N·m and 1176 ± 152 N, respectively) than MaxCTT (62 ± 12 N·m and 1085 ± 119 N, respectively). During arm cocking, maximum pelvis angular velocity was greater in MinCTT than MaxCTT and ModCTT, and maximum upper trunk angular velocity was greater in MaxCTT and ModCTT than MinCTT. At ball release, trunk forward tilt was greater in MaxCTT and ModCTT than MinCTT and greater in MaxCTT than ModCTT, while arm slot angle was less in MaxCTT and ModCTT than MinCTT and less in MaxCTT than ModCTT. The greatest shoulder and elbow peak forces occurred in ModCTT, which occurs in pitchers who throw with a three-quarter arm slot. More research is needed to assess if pitchers with ModCTT are at a higher risk of shoulder and elbow injury compared with pitchers with MaxCTT (overhand arm slot) and MinCTT (sidearm arm slot), although in the pitching literature, excessive elbow and shoulder forces and torques have been shown to correlate with elbow and shoulder injuries. The results from the current study will help clinicians better understand if differences in kinematic and kinetic measures differ with pitching, or if differences in force, torque, and arm position occur at different arm slots.

This clinical commentary will address five key concepts that can be used by clinicians as criteria for selecting lower extremity weight bearing exercises (WBE) and non-weight bearing exercises (NWBE) employed for cruciate ligament and patellofemoral rehabilitation. The following will be discussed for both cruciate ligament and patellofemoral rehabilitation: 1) Knee loading varies between WBE and NWBE; 2) Knee loading varies with technique variations within WBE and NWBE; 3) Knee loading varies between different WBE; 4) Knee loading varies as a function of knee angle; and 5) Knee loading increases with increased knee anterior translation beyond toes.

Purpose. The optimal surgical technique for unstable acromioclavicular (AC) and coracoclavicular (CC) joint injuries has not yet been established. The biomechanical and radiographic effect of the LockDown device, a synthetic ligament for AC joint reconstruction, was evaluated to assess the optimal surgical technique for unstable AC and CC joint injuries. It was hypothesized that the LockDown device would restore AC joint kinematics and radiographic stability to near native values. Methods. Three fresh frozen cadaveric torsos (6 shoulders) modelled CC joint motion in their “native,” “severed,” and “reconstructed” states. The effects of stressed and unstressed native, severed, and reconstructed conditions on AC separation and CC distances in anteroposterior, mediolateral, and inferosuperior directions during shoulder abduction, flexion, and scaption were assessed. The analysis of variance (p, 0.05) was used to compare CC distance and peak AC distance in anteroposterior, mediolateral, and inferosuperior directions during shoulder flexion, abduction, and scaption measurements among native, severed, and reconstructed states with unstressed and stressed Zanca radiographic views. Results. From radiographic analyses, the CC distance was significantly greater (p=0.001) across the surgical state in stressed versus unstressed views. Mean difference between stressed and unstressed views was 1.8 mm in native state, 4.1 mm in severed state, and 0.9 mm in reconstructed state. The CC distance was significantly greater in the “severed” state (10.4 mm unstressed; 14.5 mm stressed) compared to the “native” state (p=0.016) (6.5 mm unstressed; 8.3 mm stressed) and compared to the “reconstructed” state (p=0.005) (3.1 mm unstressed; 4.0 mm stressed) and significantly less (p=0.008) in the “reconstructed” state compared to the “native” state. CC distances decreased from native to reconstructed, an average of 3.3 mm for unstressed and 4.3 mm for stressed. On average, peak AC joint separation distance in anteroposterior, mediolateral, and inferosuperior directions during shoulder-abduction, flexion, and scaption was shown to be restored to 11.5 mm of native values after reconstruction with LockDown device. Conclusion. Reconstruction of AC joint with LockDown synthetic ligament restores motion of clavicle and acromion to near native values, thereby decreasing scapular dyskinesis and enhancing AC joint stability.