Trunk Lean During a Single-Leg Squat Is Associated With Trunk Lean During Pitching

Abstract

Background: Impaired trunk motion during pitching may be a risk factor for upper extremity injuries. Specifically, increased forces about the shoulder and elbow have been observed in pitchers with excessive contralateral trunk lean during pitching. Because of the difficulty in identifying abnormal trunk motions during a high-speed task such as pitching, a clinical screening test is needed to identify pitchers who have impaired trunk motion during pitching. Hypothesis/Purpose:The purpose of this study was to determine the relationship between the degree of lateral trunk lean during the single-leg squat and amount of trunk lean during pitching and if trunk lean during pitching can be predicted from lean during the single-leg squat.Study Design: Controlled Laboratory Study; Cross-sectional.Methods: Seventy-three young baseball pitchers (11.4 ± 1.7 years; 156.3 ± 11.9 cm; 50.5 ± 8.8 kg) participated. An electromagnetic tracking system was used to obtain trunk kinematic data during a single-leg squat task (lead leg) and at maximum shoulder external rotation of a fastball pitch. Pearson correlation coefficients for trunk lean during the single-leg squat and pitching were calculated. A linear regression analysis was performed to determine if trunk lean during pitching can be predicted from lean during the single-leg squat.Results: There was a positive correlation between trunk lean during the single-leg squat and trunk lean during pitching (r= 0.53; p<0.001). Lateral trunk lean during the single-leg squat predicted the amount of lateral trunk lean during pitching (R 2 = 0.28; p< 0.001).Conclusions: A moderate positive correlation was observed between trunk lean during an SLS and pitching. Trunk lean during the single-leg squat explained 28% of the variance in trunk lean during pitching. Level of Evidence: Diagnosis, level 3

Single-Leg Squat Performance and Reported Pain within Youth Softball Players

“…Based on the fact that the SLS is a reliable assessment of LPHC strength and stability, sport performance, and lower extremity pain [9,11,14,[16][17][18], the purpose of this study to investigate the associations between bilateral SLS performance and reported pain in youth softball athletes. A positive correlation was found between bilateral differences of knee valgus at maximal knee flexion and pain.…”

“…Kinematic data were collected at 100 Hz using an electromagnetic tracking system (trackSTAR TM , Ascension Technologies, Inc., Burlington, VT, USA) synced with The MotionMonitor (Innovative Sports Training, Chicago, IL, USA). Thirteen sensors were attached to the following landmarks: (1) posterior aspect of the torso at the first thoracic vertebrae (T1) spinous process; (2) posterior aspect of the pelvis at the first sacral vertebrae (S1); (3)(4) flat, broad portion of the acromion on the bilateral scapula; (5-6) lateral aspect of bilateral upper arm at the deltoid tuberosity; (7-8) posterior aspect of bilateral distal forearm, centered between the radial and ulnar styloid processes; (9-10) lateral aspect of bilateral upper leg, centered between the greater trochanter and the lateral condyle of the knee; (10-11) lateral aspect of bilateral lower leg, centered between the head of the fibula and lateral malleolus; (12) posterior aspect of the dominate hand below the second phalanx; and (13) superior aspect of the foot, midway between the metatarsophalangeal and talocalcaneonavicular joint [9,10,14]. A fourteenth, moveable sensor was attached to a plastic stylus and used for the digitization of bony landmarks.…”

“…The investigator then demonstrated an acceptable and unacceptable trial for each participant. A trial was deemed acceptable if the participant squatted down as far as possible and then rose to their initial position without the raised leg contacting the ground or stance leg [9,10,14]. Prior to testing, participants were allowed to practice the SLS.…”

“…Clinically, LPHC stability has been assessed and validated through the use of a single-leg squat (SLS) [7,14]. When considering the ability of the LPHC to stabilize both the lower extremity and trunk, clinicians commonly rely on the assessment of the SLS [15,16].…”

“…When considering the ability of the LPHC to stabilize both the lower extremity and trunk, clinicians commonly rely on the assessment of the SLS [15,16]. It has been found that the SLS squat test is a reliable assessment of LPHC strength and stability [11,16], plane specific knee mechanics, sport performance [9,14,17], and lower extremity pain [18]. Based on the dynamic nature of the overhead throwing motion and the need for proximal stability of the lower extremity and LPHC, utilization of the SLS as a mechanism of screening for injury susceptibility though the examination of pain prevalence could prove beneficial [8,10,11,14].…”