Reliability of an electromagnetic tracking system in describing pitching mechanics

Single-Leg Squat Compensations Are Associated With Softball Pitching Pathomechanics in Adolescent Softball Pitchers

Background:

A lack of lumbopelvic-hip complex (LPHC) stability is often associated with altered pitching mechanics, thus increasing pain and injury susceptibility. The single-leg squat (SLS) is a simple diagnostic tool used to examine LPHC stability.

Purpose:

To examine the relationship between trunk compensatory kinematics during the SLS and kinematics at foot contact during the windmill pitch.

Study Design:

Descriptive laboratory study.

Methods:

Participants included 55 youth and high school softball pitchers (mean age, 12.6 ± 2.2 years; height, 160.0 ± 11.0 cm; weight, 60.8 ± 15.5 kg). Kinematic data were collected at 100 Hz using an electromagnetic tracking device. Participants were asked to complete an SLS on each leg, then throw 3 fastballs at maximal effort. Values of trunk flexion, trunk lateral flexion, and trunk rotation at peak depth of the SLS were used as the dependent variables in 3 separate backward-elimination regression analyses. Independent variables examined at foot contact of the pitch were as follows: trunk flexion, trunk lateral flexion, trunk rotation, center of mass, stride length, and stride knee valgus.

Results:

The SLS trunk rotation regression (F(1,56) = 4.980, P = .030) revealed that trunk flexion predicted SLS trunk rotation (SE = 0.068, t = 2.232, P = .030) and explained approximately 7% of the variance in SLS trunk rotation (R² = 0.083, adjusted R² = 0.066). The SLS trunk flexion regression (F(1,56) = 5.755, P = 0.020) revealed that stride knee valgus significantly predicted SLS trunk flexion (SE = 0.256, t = 2.399, P = .020) and explained approximately 8% of variance in SLS trunk flexion (R² = 0.095, adjusted R² = 0.078).

Conclusion:

Additional trunk rotation and trunk flexion at peak depth of the SLS showed increased knee valgus and trunk flexion at foot contact of the pitch, both of which indicate poor LPHC stability during the softball pitch and may increase the potential for injury.

Clinical Relevance:

Players and coaches should implement SLS analyses to determine their players’ risk for injury and compensation due to poor core stability.

Relationship Between Humeral Energy Flow During the Baseball Pitch and Glenohumeral Stability

Researchers suggest that motion deriving energy from the more proximal segments of the body is important to reduce injury susceptibility. However, limited clinical assessments have been associated with efficient energy flow within a complex movement such as the baseball pitch. This research aimed to determine the relationship between glenohumeral stability as determined by the closed kinetic chain upper extremity stability test and energy transfer into and out of the humerus during the baseball pitching motion. Kinematic and kinetic data were collected at 240 Hz on twenty-four baseball pitchers. Participants performed the closed kinetic chain upper extremity stability test prior to throwing three fastballs at game speed to a catcher with the fastest fastball used for analysis. Spearman's Rho were used to examine relationships between energy flow in and out of the humerus with glenohumeral stability as determined by the average score and normalized stance width during the closed kinetic chain upper extremity stability test. There was a significant negative correlation between the average score and normalized peak power leaving the humerus (r _s[22]=-0.42, p=0.04). This result provides preliminary support for the use of the closed kinetic chain upper extremity stability test as a clinical assessment of a pitcher's ability to efficiently transfer energy within the upper extremity during the pitch.

Glenohumeral external rotation weakness partially accounts for increased humeral rotation torque in youth baseball pitchers

OBJECTIVES

To examine differences in shoulder internal rotation (IR) torque among youth pitchers of above and below average relative glenohumeral (GH) rotation strength levels. It was hypothesized that differences in IR torque during the pitching motion would could be explained by differences in relative IR and external rotation (ER) strength.

DESIGN

Descriptive laboratory study.

METHODS

Isometric GH rotation strength and upper extremity pitching mechanics were assessed in 78 male youth baseball pitchers (12.7±2.0yrs; 1.63±14.0m; 56.9±12.4kg). Shoulder IR torque during the pitch was examined at maximum humeral external rotation (MER) and throughout the arm acceleration phase (ACC). Multivariate analysis of covariance (MANCOVA) was used to examine the differences in pitching IR torque between GH strength groups.

RESULTS

A significant main effect of ER strength on the dependent variables was present after controlling for fastball velocity (λ=0.855, F_2,72=6.13, p=0.003, η_p²=0.145). Follow up univariate tests indicated significant differences in IR torque between strength groups at MER (F_1,73=12.36, p<0.001, η_p²=0.145) and during ACC (F_1,73=6.65, p= 0.012, η_p²=0.083). Participants who displayed ER strength at or below the group mean experienced greater IR torque at MER and greater average IR torque during ACC than participants who displayed ER strength above the group mean.

CONCLUSIONS

Weakness of the GH ER musculature partially accounts for increased shoulder IR torque during pitching.

Using the single leg squat as an assessment of stride leg knee mechanics in adolescent baseball pitchers

OBJECTIVES

Lack of control of the lower extremity or trunk during single leg tasks is often associated with pathomechanic adaptations during the pitching motion which may increase the risk of pain and injury to the upper extremity. The objectives of the study were to determine the amount of variability in stride knee mechanics accounted for by compensations during a common movement assessment, the single leg squat (SLS) and to establish the usefulness of SLS as a screening tool for at-risk athletes.

DESIGN

Cross-sectional design.

METHODS

Sixty-one adolescent baseball pitchers performed a SLS on each leg. Participants performed three fastball pitches to a catcher at a regulation distance. Kinematic data were collected at 100Hz using an electromagnetic tracking device.

RESULTS

MANOVAs with follow-up one-way ANOVAs were used to examine the amount of variance in pitching knee mechanics explained by SLS compensations. At stride foot contact, there was a significant effect of SLS valgus angle on knee valgus angle (F_1,51=23.16, p<0.001, η_p²=0.31) and valgus moment (F_1,51=8.28, p=0.006, η_p²=0.14). At ball release (BR), there was a significant effect of SLS valgus angle on flexion angle (F_1,51=9.37, p=0.004, η_p²=0.16) and valgus angle (F_1,51 = 26.93, p<0.001, η_p²=0.35). Examination of the average values occurring between SFC and BR, revealed a significant effect of SLS valgus angle on knee valgus angle (F_1,51=30.91, p<0.001, η_p²=0.38).

CONCLUSIONS

SLS compensations are potentially a useful screening tool for stride knee mechanics in adolescent baseball pitchers.