Patellofemoral Joint Loading during the Performance of the Wall Squat and Ball Squat with Heel-to-Wall-Distance Variations.

INTRODUCTION: Although 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 vs wall squat) and between two heel-to-wall-distance (HTWD) variations (long HTWD vs short HTWD). METHODS: 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, whereas electromyographic data were used in a knee muscle model to predict resultant knee force and torque, and subsequently, all these data were inputted into a biomechanical computer optimization model to output patellofemoral joint force and stress at select knee angles. A repeated-measures two- and three-way ANOVA ( P < 0.01) was used for statistical analyses. RESULTS: 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 angles 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 angles during squat ascent. Collapsed across ball and wall squats, patellofemoral joint force and stress were greater with a short HTWD than a long HTWD at 100° ( P = 0.007) and 90° ( P = 0.008) knee angles during squat ascent. CONCLUSIONS: 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 with 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 with squatting with long HTWD.

Patellofemoral Joint Loading in Forward Lunge With Step Length and Height Variations.

The objective was to assess how patellofemoral loads (joint force and stress) change while lunging with step length and step height variations. Sixteen participants performed a forward lunge using short and long steps at ground level and up to a 10-cm platform. Electromyography, ground reaction force, and 3D motion were captured, and patellofemoral loads were calculated as a function of knee angle. Repeated-measures 2-way analysis of variance (P < .05) was employed. Patellofemoral loads in the lead knee were greater with long step at the beginning of landing (10°-30° knee angle) and the end of pushoff (10°-40°) and greater with short step during the deep knee flexion portion of the lunge (50°-100°). Patellofemoral loads were greater at ground level than 10-cm platform during lunge descent (50°-100°) and lunge ascent (40°-70°). Patellofemoral loads generally increased as knee flexion increased and decreased as knee flexion decreased. To gradually increase patellofemoral loads, perform forward lunge in the following sequence: (1) minimal knee flexion (0°-30°), (2) moderate knee flexion (0°-60°), (3) long step and deep knee flexion (0°-100°) up to a 10-cm platform, and (4) long step and deep knee flexion (0°-100°) at ground level.

Patellofemoral Joint Loading During the Performance of the Forward and Side Lunge with Step Height Variations.

BACKGROUND: Forward and side lunge exercises strengthen hip and thigh musculature, enhance patellofemoral joint stability, and are commonly used during patellofemoral rehabilitation and training for sport. HYPOTHESIS/PURPOSE: The purpose was to quantify, via calculated estimates, patellofemoral force and stress between two lunge type variations (forward lunge versus side lunge) and between two step height variations (ground level versus 10 cm platform). The hypotheses were that patellofemoral force and stress would be greater at all knee angles performing the bodyweight side lunge compared to the bodyweight forward lunge, and greater when performing the forward and side lunge at ground level compared to up a 10cm platform. STUDY DESIGN: Controlled laboratory biomechanics repeated measures, counterbalanced design. METHODS: Sixteen participants performed a forward and side lunge at ground level and up a 10cm platform. Electromyographic, ground reaction force, and kinematic variables were collected and input into a biomechanical optimization model, and patellofemoral joint force and stress were calculated as a function of knee angle during the lunge descent and ascent and assessed with a repeated measures 2-way ANOVA (p<0.05). RESULTS: At 10° (p=0.003) knee angle (0° = full knee extension) during lunge descent and 10° and 30° (p<0.001) knee angles during lunge ascent patellofemoral joint force and stress were greater in forward lunge than side lunge. At 40°(p=0.005), 50°(p=0.002), 60°(p<0.001), 70°(p=0.006), 80°(p=0.005), 90°(p=0.002), and 100°(p<0.001) knee angles during lunge descent and 50°(p=0.002), 60°(p<0.001), 70°(p<0.001), 80°(p<0.001), and 90°(p<0.001) knee angles during lunge ascent patellofemoral joint force and stress were greater in side lunge than forward lunge. At 60°(p=0.009) knee angle during lunge descent and 40°(p=0.008), 50°(p=0.009), and 60°(p=0.007) knee angles during lunge ascent patellofemoral joint force and stress were greater lunging at ground level than up a 10cm platform. CONCLUSIONS: Patellofemoral joint loading changed according to lunge type, step height, and knee angle. Patellofemoral compressive force and stress were greater while lunging at ground level compared to lunging up to a 10 cm platform between 40° - 60° knee angles, and greater while performing the side lunge compared to the forward lunge between 40° - 100° knee angles. LEVEL OF EVIDENCE: II.

Arthroscopic Knotless Remplissage for the Treatment of Hill-Sachs Lesions Using the PASTA Bridge Configuration.

Recurrent glenohumeral dislocations can produce Hill-Sachs lesions-bony defects on the humeral head resulting from the humerus hitting the glenoid during dislocations. Some of these lesions can engage on the glenoid during motion, producing instability and potentially affecting the success of a labral repair. The remplissage was developed to address these Hill-Sachs lesions and improve stability. French for "filling," the goal of the remplissage is to fill the Hill-Sachs lesion with the infraspinatus tendon, preventing the margins of the lesion from engaging with the glenoid. Analogous to restoring the rotator cuff footprint during repair, a primary goal of the remplissage is to have the infraspinatus cover the Hill-Sachs lesion. The partial articular supraspinatus tendon avulsion (PASTA) bridge was originally developed for partial-thickness rotator cuff repair in situ, but additional uses have been found in other settings. The PASTA bridge uses a medial row horizontal mattress with a lateral anchor to create a linked construct to effectively distribute force and provide adequate coverage of the lesion. Knotless anchor technology used in this procedure prevents the need for arthroscopic knot tying and potentially damaging knot stacks. This Technical Note describes a remplissage technique using the PASTA bridge configuration to address Hill-Sachs lesions associated with recurrent glenohumeral instability.

Effects of a Short-Duration Stretching Drill After Pitching on Elbow and Shoulder Range of Motion in Professional Baseball Pitchers.

BACKGROUND: A glenohumeral internal rotation (IR) deficit or a total rotational motion (IR plus external rotation [ER]) deficit in the throwing shoulder compared with the nonthrowing shoulder has been shown to increase the risk of shoulder and elbow injuries. After a pitching session, both IR and total rotational motion deficits have been shown to occur naturally for an extended period of time in asymptomatic pitchers, but it is unclear how to best control these deficits between pitching sessions. Purpose/Hypothesis: The purpose of this study was to determine whether performing a short-duration stretching/calisthenics drill after pitching will result in an increase in IR, ER, total rotational motion, and elbow extension in professional baseball pitchers. It was hypothesized that these shoulder and elbow passive range of motion (PROM) measurements would all decrease after pitching but would subsequently return to prepitching values after the short-duration stretching/calisthenics drill. STUDY DESIGN: Controlled laboratory study. METHODS: A convenience sample of 20 male professional baseball pitchers served as study participants. The following sequence of activities was performed for all participants: (1) a 5- to 10-minute dynamic warm-up consisting of running and light throwing, (2) elbow extension and IR and ER PROM measurements taken before pitching, (3) 40 full-effort pitches off the pitching mound, (4) 8 minutes of rest, (5) elbow extension and IR and ER PROM measurements taken after pitching, (6) a short-duration stretching/calisthenics drill (two-out drill), and (7) elbow extension and IR and ER PROM measurements taken after the two-out drill. A 1-way repeated-measures analysis of variance ( P < .05) was employed to assess differences in elbow extension, IR, ER, and total rotational motion in the 3 measurement conditions (prepitching, postpitching, and postdrill). To assess intrarater and interrater reliability, intraclass correlation coefficients (ICCs) were calculated, and the measurement error was calculated using the standard error of measurement (SEM). RESULTS: Significant differences were observed among the 3 conditions for ER ( P = .002), IR ( P = .027), and total rotational motion ( P < .001), but there was no significant difference in elbow extension ( P = .117). Bonferroni post hoc analyses revealed (1) significantly greater ER during prepitching and postdrill versus the postpitching condition (94° ± 7° [prepitching] and 94° ± 8° [postdrill] vs 88° ± 8°; P = .010 and .005, respectively), (2) significantly greater IR during prepitching and postdrill versus the postpitching condition (36° ± 10° [prepitching] and 35° ± 9° [postdrill] vs 30° ± 10°; P = .034 and .043, respectively), and (3) significantly greater total rotational motion during prepitching and postdrill versus the postpitching condition (129° ± 13° [prepitching] and 129° ± 13° [postdrill] vs 119° ± 13°; P = .034 and .004, respectively). There were no significant differences in ER, IR, or total rotational motion between the prepitching and postdrill conditions ( P > .999 for all). The intrarater reliability (ICC3,1) was 0.91 for ER (SEM, 1.3°) and 0.90 for IR (SEM, 1.9°), and the interrater reliability (ICC2,1) was 0.81 for ER (SEM, 3.3°) and 0.77 for IR (SEM, 4.3°). CONCLUSION: After a 40-pitch bullpen session, IR and ER PROM as well as total rotational motion were significantly lower than prepitching values; however, these deficits were restored back to their prepitching levels after the players performed the two-out drill, which may increase pitching performance and decrease the risk of shoulder and elbow injuries. More research is needed to test these hypotheses and assess the clinical efficacy of the two-out drill. CLINICAL RELEVANCE: The findings from the current study will assist clinicians better understand the positive effects of performing a short duration stretching/calisthenics drill on shoulder internal and external rotation range of motion between innings while pitching during a baseball game.

AN ELECTROMYOGRAPHIC ANALYSIS OF THE SHOULDER COMPLEX MUSCULATURE WHILE PERFORMING EXERCISES USING THE BODYBLADE® CLASSIC AND BODYBLADE® PRO.

BACKGROUND: In spite of the bodyblade (BB®) being used in clinical settings during shoulder and trunk rehabilitation and training for 24 years, there are only five known scientific papers that have described muscle recruitment patterns using the BB®. Moreover, there are no known studies that have examined muscle activity differences between males and females (who both use the bodyblade in the clinic) or between different BB® devices. HYPOTHESIS/PURPOSE: The primary purposes of this investigation were to compare glenohumeral and scapular muscle activity between the Bodyblade® Pro (BB®P) and Bodyblade® Classic (BB®C) devices while performing a variety of exercises, as well as to compare muscle activity between males and females. It was hypothesized that glenohumeral and scapular muscle activity would be significantly greater in females compared to males, significantly greater while performing exercises with the BB®P compared to the BB®C, significantly different among various BB® exercises, and greater with two hand use compared to one hand use for the same exercise. STUDY DESIGN: Controlled laboratory study using a repeated-measures, counterbalanced design. METHODS: Twenty young adults, 10 males and 10 females, performed seven BB® exercises using the BB®C and BB®P, which are: 1) BB®1 - one hand, up and down motion, arm at side; 2) BB®2 - one hand, front to back motion, shoulder flexed 90 °; 3) BB®3 - one hand, up and down motion, shoulder abducted 90 °; 4) BB®4 - one hand, side to side motion, shoulder and elbow flexed 45 °; 5) BB®5 - two hands, side to side motion, shoulders and elbows flexed 45 °; 6) BB®6 - two hands, up and down motion, shoulders flexed 90 °; and 7) BB®7 - two hands, front to back motion, shoulders flexed 90 °. EMG data were collected from anterior and posterior deltoids, sternal pectoralis major, latissimus dorsi, infraspinatus, upper and lower trapezius, and serratus anterior during 10 sec of continuous motion for each exercise, and then normalized using maximum voluntary isometric contractions (MVIC). A two-factor repeated measures Analysis of Variance (p < 0.05) was employed to assess differences in EMG activity between BB® devices (BB®C and BB®P) and genders. RESULTS: As hypothesized, for numerous exercises and muscles glenohumeral and scapular EMG activity was significantly greater in females compared to males and was significantly greater in the BB®P compared to BB®C. There were generally no significant interactions between BB® devices and gender. Overall glenohumeral and scapular muscle activity was significantly greater in BB®3 and BB®6 compared to the remaining exercises, but generally not significantly different between using one hand and using two hands. CONCLUSIONS: It may be appropriate to employ BB® exercises during shoulder rehabilitation earlier for males compared to females and earlier for the BB®C compared to the BB®P given less overall muscle activation in males and BB®C compared to in females and BB®P. There was generally no difference in muscle activity between performing the BB® with one-hand or two-hands. Differences in muscle activity between exercises generally was the similar regardless if the BB®C or the BB®P was employed. LEVEL OF EVIDENCE: Level 2.

Comparison of three baseball-specific 6-week training programs on throwing velocity in high school baseball players.

Throwing velocity is an important baseball performance variable for baseball pitchers, because greater throwing velocity results in less time for hitters to make a decision to swing. Throwing velocity is also an important baseball performance variable for position players, because greater throwing velocity results in decreased time for a runner to advance to the next base. This study compared the effects of 3 baseball-specific 6-week training programs on maximum throwing velocity. Sixty-eight high school baseball players 14-17 years of age were randomly and equally divided into 3 training groups and a nontraining control group. The 3 training groups were the Throwers Ten (TT), Keiser Pneumatic (KP), and Plyometric (PLY). Each training group trained 3 d·wk(-1) for 6 weeks, which comprised approximately 5-10 minutes for warm-up, 45 minutes of resistance training, and 5-10 for cool-down. Throwing velocity was assessed before (pretest) and just after (posttest) the 6-week training program for all the subjects. A 2-factor repeated measures analysis of variance with post hoc paired t-tests was used to assess throwing velocity differences (p < 0.05). Compared with pretest throwing velocity values, posttest throwing velocity values were significantly greater in the TT group (1.7% increase), the KP group (1.2% increase), and the PLY group (2.0% increase) but not significantly different in the control group. These results demonstrate that all 3 training programs were effective in increasing throwing velocity in high school baseball players, but the results of this study did not demonstrate that 1 resistance training program was more effective than another resistance training program in increasing throwing velocity.

Effects of a 4-week youth baseball conditioning program on throwing velocity.

Effects of a 4-week youth baseball conditioning program on throwing velocity. This study examined the effects of a 4-week youth baseball conditioning program on maximum throwing velocity. Thirty-four youth baseball players (11-15 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (each 75 minutes) weekly for 4 weeks, which comprised a sport specific warm-up, resistance training with elastic tubing, a throwing program, and stretching. Throwing velocity was assessed initially and at the end of the 4-week conditioning program for both control and training groups. The level of significance used was p < 0.05. After the 4-week conditioning program, throwing velocity increased significantly (from 25.1 ± 2.8 to 26.1 ± 2.8 m·s) in the training group but did not significantly increase in the control group (from 24.2 ± 3.6 to 24.0 ± 3.9 m·s). These results demonstrate that the short-term 4-week baseball conditioning program was effective in increasing throwing velocity in youth baseball players. Increased throwing velocity may be helpful for pitchers (less time for hitters to swing) and position players (decreased time for a runner to advance to the next base).

Shoulder muscle activity and function in common shoulder rehabilitation exercises.

The rotator cuff performs multiple functions during shoulder exercises, including glenohumeral abduction, external rotation (ER) and internal rotation (IR). The rotator cuff also stabilizes the glenohumeral joint and controls humeral head translations. The infraspinatus and subscapularis have significant roles in scapular plane abduction (scaption), generating forces that are two to three times greater than supraspinatus force. However, the supraspinatus still remains a more effective shoulder abductor because of its more effective moment arm. Both the deltoids and rotator cuff provide significant abduction torque, with an estimated contribution up to 35-65% by the middle deltoid, 30% by the subscapularis, 25% by the supraspinatus, 10% by the infraspinatus and 2% by the anterior deltoid. During abduction, middle deltoid force has been estimated to be 434 N, followed by 323 N from the anterior deltoid, 283 N from the subscapularis, 205 N from the infraspinatus, and 117 N from the supraspinatus. These forces are generated not only to abduct the shoulder but also to stabilize the joint and neutralize the antagonistic effects of undesirable actions. Relatively high force from the rotator cuff not only helps abduct the shoulder but also neutralizes the superior directed force generated by the deltoids at lower abduction angles. Even though anterior deltoid force is relatively high, its ability to abduct the shoulder is low due to a very small moment arm, especially at low abduction angles. The deltoids are more effective abductors at higher abduction angles while the rotator cuff muscles are more effective abductors at lower abduction angles. During maximum humeral elevation the scapula normally upwardly rotates 45-55 degrees, posterior tilts 20-40 degrees and externally rotates 15-35 degrees. The scapular muscles are important during humeral elevation because they cause these motions, especially the serratus anterior, which contributes to scapular upward rotation, posterior tilt and ER. The serratus anterior also helps stabilize the medial border and inferior angle of the scapular, preventing scapular IR (winging) and anterior tilt. If normal scapular movements are disrupted by abnormal scapular muscle firing patterns, weakness, fatigue, or injury, the shoulder complex functions less efficiency and injury risk increases. Scapula position and humeral rotation can affect injury risk during humeral elevation. Compared with scapular protraction, scapular retraction has been shown to both increase subacromial space width and enhance supraspinatus force production during humeral elevation. Moreover, scapular IR and scapular anterior tilt, both of which decrease subacromial space width and increase impingement risk, are greater when performing scaption with IR ('empty can') compared with scaption with ER ('full can'). There are several exercises in the literature that exhibit high to very high activity from the rotator cuff, deltoids and scapular muscles, such as prone horizontal abduction at 100 degrees abduction with ER, flexion and abduction with ER, 'full can' and 'empty can', D1 and D2 diagonal pattern flexion and extension, ER and IR at 0 degrees and 90 degrees abduction, standing extension from 90-0 degrees , a variety of weight-bearing upper extremity exercises, such as the push-up, standing scapular dynamic hug, forward scapular punch, and rowing type exercises. Supraspinatus activity is similar between 'empty can' and 'full can' exercises, although the 'full can' results in less risk of subacromial impingement. Infraspinatus and subscapularis activity have generally been reported to be higher in the 'full can' compared with the 'empty can', while posterior deltoid activity has been reported to be higher in the 'empty can' than the 'full can'.