Does High Medial Elbow Stress During Pitching Compromise the Dynamic Stabilizers of The Elbow?

Background

The flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS) are thought to provide dynamic stability to the medial elbow, with a lesser contribution from the pronator teres (PT).

Hypothesis/Purpose

The purpose of this study was to determine if baseball pitchers with higher valgus elbow torque experience greater FCU and FDS strength loss.

Study Design

Controlled Laboratory Study.

Methods

A pilot study was performed to determine if middle and ring finger flexion strength tests preferentially activated the FCU and FDS versus the PT (10 men age 36±12 yr). EMG amplitudes, expressed as percent of maximal voluntary contraction (MVC) were compared between tests and muscles. In a field study of college baseball pitchers, middle finger, ring finger and grip strength were tested prior to, immediately after, and one day after 14 pitching performances in 10 pitchers (21±2 yr). Elbow valgus torque was measured from an inertial measurement unit, housed in a compression sleeve and pitchers were categorized as having high or low valgus torque.

Results

For the pilot study EMG activations were 74% FDS, 66% FCU and 35% PT for the middle finger test (muscle effect p=0.032) and 93% FCU, 61% FDS and 23% PT for the ring finger test (muscle effect p=0.005). In the field study, pitchers with high valgus torque showed marked post-game middle finger fatigue (88% of baseline) and incomplete recovery the following day (95%), while pitchers with low valgus torque showed no strength loss (107% post game, 106% a day later; group x time p=0.022). Results were similar for ring finger strength (high torque: 94% post game 96% a day later; low torque: 114% post game 107% a day later; group x time p=0.048). By contrast, grip strength was not different between pitchers with high versus low valgus torque (p=0.143).

Conclusion

High medial elbow stress during pitching fatigues the dynamic stabilizers of the medial elbow.

Level of Evidence

Level 3©The Author(s).

Role of Pelvis and Trunk Biomechanics in Generating Ball Velocity in Baseball Pitching

ABSTRACT

Orishimo, KF, Kremenic, IJ, Mullaney, MJ, Fukunaga, T, Serio, N, and McHugh, MP. Role of pelvis and trunk biomechanics in generating ball velocity in baseball pitching. J Strength Cond Res 37(3): 623-628, 2023-The purpose of this study was to determine the impact of pelvis rotation velocity, trunk rotation velocity, and hip-shoulder separation on ball velocity during baseball pitching. Fastball pitching kinematics were recorded in 29 male pitchers (age 17 ± 2 years, 23 high school, 6 college). Pelvis and trunk angular velocities and hip-shoulder separation were calculated and averaged for the 3 fastest pitches. Associations between peak pelvis velocity, peak trunk velocity, hip-shoulder separation at foot contact, and ball velocity were assessed using Pearson correlation coefficients and multiple regression. The average ball velocity was 33.5 ± 2.8 m·s -1 . The average hip-shoulder separation at foot contact was 50 ± 12°. The peak pelvis velocity (596 ± 88°·s -1 ) occurred at 12 ± 11% of the time from stride foot contact to ball release, with the peak trunk velocity (959 ± 120°·s -1 ) occurring at 36 ± 11%. Peak trunk velocity was predictive of ball velocity ( p = 0.002), with 25% of the variability in ball velocity explained. No combination of factors further explained ball velocity. Hip-shoulder separation at foot contact (17%, p = 0.027), peak pelvis velocity (23%, p = 0.008), and the timing of peak pelvis velocity (16%, p = 0.031) individually predicted peak trunk velocity. The combination of peak pelvis velocity, hip-shoulder separation at foot contact, and the timing of peak trunk velocity explained 55% of the variability in trunk rotation velocity ( p < 0.001). These data highlight the importance of interactions between pelvis and trunk for maximizing velocity in pitching. Training to improve pelvis-trunk axial dissociation may increase maximal trunk rotation velocity and thereby increase ball velocity without increasing training load on the shoulder and elbow.

Accelerated Muscle Recovery in Baseball Pitchers Using Phase Change Material Cooling

PURPOSE

The purpose of this study was to document recovery after a pitching performance and determine whether prolonged postgame phase change material (PCM) cooling of the shoulder and forearm accelerates recovery.

METHODS

Strength, soreness, and serum creatine kinase (CK) activity were assessed before and on the 2 d after pitching performances in 16 college pitchers. Pitchers were randomized to receive either postgame PCM cooling packs on the shoulder and forearm or no cooling (control). PCM packs were applied inside compression shirts and delivered cooling at a constant temperature of 15°C for 3 h. Strength was assessed for shoulder internal rotation (IR), external rotation (ER), empty can (EC) test, and grip.

RESULTS

Total pitch count was 60 ± 16 for 23 PCM cooling games and 62 ± 17 for 24 control games (P = 0.679). On the days after pitching, IR strength (P = 0.006) and grip strength (P = 0.036) were higher in the PCM cooling group versus control. One day after pitching, IR strength was 95% ± 14% of baseline with PCM cooling versus 83% ± 13% for control (P = 0.008, effect size d = 0.91) and 107% ± 9% versus 95% ± 10% for grip strength (P = 0.022, effect size d = 1.29). There was a trend for greater ER strength with PCM cooling (P = 0.091, effect size d = 0.51). The EC strength was not impaired after pitching (P = 0.147) and was therefore unaffected by PCM cooling (P = 0.168). Elevations in soreness and CK were not different between treatments (treatment-time CK P = 0.139, shoulder soreness P = 0.885, forearm soreness P = 0.206).

CONCLUSION

This is one of the first studies to document impairments in muscle function on the days after baseball pitching, and the first study showing a novel cryotherapy intervention that accelerates recovery of muscle function in baseball pitchers after a game.

EMG OF SHOULDER MUSCLES DURING REACTIVE ISOMETRIC ELASTIC RESISTANCE EXERCISES

BACKGROUND

Traditionally, shoulder isometrics are introduced in the early stages of shoulder rehabilitation. A patient's isometric torque output is based on a subjective perception of force generation. By utilizing elastic resistance elongation (strain) to standardize force output, clinicians could prescribe shoulder therapeutic isometrics based on % maximum voluntary contraction (%MVC).

PURPOSE/HYPOTHESIS

The purpose of this study was to measure electromyographic (EMG) activity and determine the %MVC during shoulder flexion, external rotation and abduction isometrics at varying lengths of TheraBand® elastic resistance. It was hypothesized that increased elongation of progressive resistance bands would proportionately increase the %MVC of the shoulder musculature.

STUDY DESIGN

Laboratory design using healthy subjects.

METHODS

Eight healthy subjects (16 shoulders) (5 females, 3 males; avg. age 29.2) were tested. Surface EMG electrodes were placed over the anterior deltoid, middle deltoid, and infraspinatus muscles. A force transducer was anchored to a stable surface with its corresponding end in series with an extremity strap securely holding the elastic band. Subjects were asked to maintain shoulder position for the proper isometric contraction (flexion, abduction and external rotation) while taking incremental steps away from the anchored elastic resistance, to the beat of a metronome to clearly marked distances on the floor (50, 100, 150, 200 and 250% of band elongation). This was repeated with yellow, red, green, and blue TheraBand® resistance levels. Maximum voluntary contractions for both force and EMG were collected for each subject in all three test positions. EMG data were normalized and expressed as a %MVC.

RESULTS

For external rotation and flexion, the infraspinatus and anterior deltoid activity increased with band elongation (p<0.01) and progressive colors (p<0.01). The increases in EMG activity with elongation plateaued with the yellow and red bands but continued to increase with the green and blue bands (p<0.01). The increase in infraspinatus and anterior deltoid EMG activity with progressive band color was more apparent for green and blue bands compared with yellow and red band (p<0.01). For the abduction exercise, middle deltoid activity increased with band elongation (p<0.01) and progressive color (p<0.01). In all three exercises, there was an increase in force exerted by the band with increasing length and band color (p < 0.001). However, while there were clear increases in force from red to green to blue, there was no difference in force between yellow and red regardless of elongation (p<0.01).

CONCLUSION

Isometric flexion, external rotation and abduction muscle activity can be accurately prescribed clinically by adjusting the elongation and resistance associated with progressive colors of resistance bands.

LEVEL OF EVIDENCE

3.

CURRENT CONCEPTS AND TREATMENT OF PATELLOFEMORAL COMPRESSIVE ISSUES

Patellofemoral disorders, commonly encountered in sports and orthopedic rehabilitation settings, may result from dysfunction in patellofemoral joint compression. Osseous and soft tissue factors, as well as the mechanical interaction of the two, contribute to increased patellofemoral compression and pain. Treatment of patellofemoral compressive issues is based on identification of contributory impairments. Use of reliable tests and measures is essential in detecting impairments in hip flexor, quadriceps, iliotibial band, hamstrings, and gastrocnemius flexibility, as well as in joint mobility, myofascial restrictions, and proximal muscle weakness. Once relevant impairments are identified, a combination of manual techniques, instrument-assisted methods, and therapeutic exercises are used to address the impairments and promote functional improvements. The purpose of this clinical commentary is to describe the clinical presentation, contributory considerations, and interventions to address patellofemoral joint compressive issues.

Functional Outcomes After Double-Row Versus Single-Row Rotator Cuff Repair: A Prospective Randomized Trial

Background:

The functional benefits of double-row (DR) versus single-row (SR) rotator cuff repair are not clearly established.

Purpose:

To examine the effect of DR versus SR rotator cuff repair on functional outcomes and strength recovery in patients with full-thickness tears.

Study Design:

Randomized controlled trial; Level of evidence, 2.

Methods:

Forty-nine patients were randomized to DR or SR repairs; 36 patients (13 women, 23 men; mean age, 62 ± 7 years; 20 SR, 16 DR) were assessed at a mean 2.2 ± 1.6 years after surgery (range, 1-7 years; tear size: 17 medium, 13 large, 9 massive). The following data were recorded prior to surgery and at follow-up: Penn shoulder score, American Shoulder and Elbow Surgeons (ASES), and Simple Shoulder Test (SST) results; range of motion (ROM) for shoulder flexion, external rotation (ER) at 0° and 90° of abduction, and internal rotation (IR) at 90° of abduction; and shoulder strength (Lafayette manual muscle tester) in empty- and full-can tests, abduction, and ER at 0° of abduction. Treatment (SR vs DR) × time (pre- vs postoperative) mixed-model analysis of variance was used to assess the effect of rotator cuff repair.

Results:

Rotator cuff repair markedly improved Penn, ASES, and SST scores (P < .001), with similar improvement between SR and DR repairs (treatment × time, P = .38-.10) and excellent scores at follow-up (DR vs SR: Penn, 91 ± 11 vs 92 ± 11 [P = .73]; ASES, 87 ± 12 vs 92 ± 12 [P = .21]; SST, 11.4 ± 1.0 vs 11.3 ± 1.0 [P = .76]). Patients with DR repairs lost ER ROM at 0° of abduction (preoperative to final follow-up, 7° ± 10° loss [P = .013]). ER ROM did not significantly change with SR repair (5° ± 14° gain, P = .16; treatment by time, P = .008). This effect was not apparent for ER ROM at 90° of abduction (treatment × time, P = .26). IR ROM improved from preoperative to final follow-up (P < .01; SR, 17° ± 27°; DR, 7° ± 21°; treatment × time, P = .23). Rotator cuff repair markedly improved strength in empty-can (54%), full-can (66%), abduction (47%), and ER (54%) strength (all P < .001), with no difference between SR and DR repairs (P = .23-.75). All clinical tests with the exception of the lift-off test were normalized at follow-up (P < .05).

Conclusion:

Outcomes were not different between SR or DR repair, with generally excellent outcomes for both groups. Rotator cuff repair and subsequent rehabilitation markedly improved shoulder strength.

The Effect of a High Pitch Volume on Musculoskeletal Adaptations in High School Baseball Pitchers

BACKGROUND

Shoulder range of motion and strength adaptations occur at an early age in baseball pitchers.

PURPOSE/HYPOTHESIS

The purpose of this study was to examine the effect of pitch volume on in-season and year-to-year range of motion (ROM) and strength adaptations in high school baseball pitchers. The hypothesis was that a high pitch volume will not affect range of motion asymmetries but will impair supraspinatus strength.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Pre- and postseason ROM and strength measures were performed on pitchers from 3 high schools for 4 consecutive seasons, for a total of 95 player-seasons (mean ± SD participant age, 16 ± 1 years). Preseason measures were repeated the next year on players returning to the teams, for a total of 71 consecutive player-seasons. ROM tests included internal-external rotation and posterior shoulder flexibility. Strength tests (hand-held dynamometer) included internal-external rotation, supraspinatus, and scapular retraction. Pitchers were categorized by pitch count for the season (high, >400; moderate, 180-400; low, <180). ROM and strength changes in the dominant versus nondominant arm were assessed by analysis of variance.

RESULTS

Dominant versus nondominant ROM differences did not change from pre- to postseason (P = .36-.99) or from one year to the next (P = .46-.86), with no effect of pitch volume (P = .23-.87). Supraspinatus strength decreased in the dominant arm during the season, with 13% loss in high-volume pitchers (P < .001) and insignificant losses in moderate- (6%) and low-volume pitchers (2%). Strength in other tests was unaffected by pitch volume. Consistent with physical development, strength increased bilaterally from one year to the next (supraspinatus, 12%; external rotation, 15%; internal rotation, 14%; scapular retraction, 23%; P < .001). Supraspinatus strength gain in the dominant arm was affected by prior pitch volume (P = .02): 24% in low-volume pitchers (P < .01), with no significant change in moderate-volume (0%; P = .99) or high-volume (5%; P = .99) pitchers.

CONCLUSION

Dominant versus nondominant ROM differences did not progress during the season, or from one year to the next, and were unaffected by pitch volume. A high pitch volume was associated with in-season supraspinatus weakness and diminished strength gains from one year to the next. In conclusion, a high pitch volume appeared to have a catabolic effect on supraspinatus strength.

Risk Factors for Shoulder and Elbow Injuries in High School Baseball Pitchers: The Role of Preseason Strength and Range of Motion

BACKGROUND

Shoulder strength and motion deficits in high school baseball pitchers have been implicated in injury risk.

PURPOSE/HYPOTHESIS

To prospectively determine if preseason strength and range of motion (ROM) are predictive of injury in high school baseball pitchers. It was hypothesized that ROM asymmetries and weakness would be predictive of injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Preseason strength and ROM measurements were made on 101 pitchers from 4 different high schools over 4 seasons (total 166 pitcher-seasons: 25 freshman, 46 junior varsity, and 95 varsity player-seasons). Glenohumeral internal rotation (IR), glenohumeral external rotation, and posterior shoulder ROM were measured bilaterally. Strength in IR, external rotation, supraspinatus (empty-can test), and scapular retraction was measured bilaterally (handheld dynamometer). Injury incidence (injuries per 1000 pitches) was computed for players categorized as above normal (≥1 SD above the mean), normal (within 1 standard deviation of the mean), and below normal (≤1 SD below the mean) for each potential risk factor. Injury was defined as a missed game or practice because of shoulder or elbow problem.

RESULTS

There were 28 upper extremity injuries (19 shoulder, 9 elbow; incidence, 0.58 injuries/1000 pitches). There was a trend for supraspinatus weakness to be associated with increased injury risk (relative risk [RR], 3.60; 95% CI, 0.75-17.32; P = .09). When analyzing major injuries only (>3 missed games), preseason supraspinatus weakness was significantly associated with increased injury risk (RR, 4.58; 95% CI, 1.40-15.01; P = .02). Paradoxically, pitchers with no IR loss were at increased risk compared with pitchers with ≥20° loss (RR, 4.85; 95% CI, 1.01-23.29; P = .04). Other ROM and strength measures were unrelated to injury risk.

CONCLUSION

Although excessive loss of IR ROM is thought to be a risk factor for injury, the opposite was the case in this study. The absence of IR ROM loss in high school pitchers may indicate inadequate prior exposure to pitching, resulting in increased injury risk. Preseason supraspinatus weakness was associated with increased risk for a major injury, and preventative supraspinatus strengthening may be beneficial.

Adaptations in single-leg hop biomechanics following anterior cruciate ligament reconstruction

When a patient performs a clinically normal hop test based on distance, it cannot be assumed that the biomechanics are similar between limbs. The objective was to compare takeoff and landing biomechanics between legs in patients who have undergone anterior cruciate ligament reconstruction. Kinematics and ground reaction forces were recorded as 13 patients performed the single-leg hop on each leg. Distance hopped, joint range of motion, peak joint kinetics and the peak total extensor moment were compared between legs during both takeoff and landing. Average hop distance ratio (involved/noninvolved) was 93 ± 4%. Compared to the noninvolved side, knee motion during takeoff on the involved side was significantly reduced (P = 0.008). Peak moments and powers on the involved side were lower at the knee and higher at the ankle and hip compared with the noninvolved side (Side by Joint P = 0.011; P = 0.003, respectively). The peak total extensor moment was not different between legs (P = 0.305) despite a decrease in knee moment and increases in ankle and hip moments (Side by Joint P = 0.015). During landing, knee motion was reduced (P = 0.043), and peak power absorbed was decreased at the knee and hip and increased at the ankle on the involved side compared to the noninvolved side (P = 0.003). The compensations by other joints may indicate protective adaptations to avoid overloading the reconstructed knee.

Reliability of shoulder range of motion comparing a goniometer to a digital level

The clinical use of digital levels, for joint measurement, may be a viable alternative to standard goniometry. The purpose of this study was to determine the intra- and intertester reliability of a construction grade digital level compared to the standard universal goniometer for measurements for active assisted shoulder range of motion (ROM). Two experienced physical therapists measured shoulder flexion, external rotation (ER), and internal rotation (IR) ROM bilaterally, on two different occasions, in 20 patients (9 males, 11 females, 18-79 years old) with unilateral shoulder pathology, using a goniometer and a digital level. Relative reliability was assessed by using intraclass correlation coefficients (ICC), and absolute reliability was assessed by using 95% limits of agreement (LOA). Intratester ICCs ranged from 0.91 to 0.99, and LOA ranged from 3 degrees to 9 degrees for measurements made with the goniometer and digital level. Intertester ICCs ranged from 0.31 to 0.95, and LOA ranged from 6 degrees to 25 degrees . For the comparison of goniometric vs. digital level ROM, ICCs ranged from 0.71 to 0.98. ER and IR ROM were 3-5 degrees greater for the digital level than the goniometer (p < 0.01). Goniometric vs. digital level LOA ranged from 6 degrees to 11 degrees for shoulder flexion. Both measurement techniques had excellent intratester reliability, but for intertester reliability ICCs were 20% lower and LOA were 2.3 times higher than intratester values. Reliability estimates were similar between the digital level and the goniometer. However, because glenohumeral rotation was 3-5 degrees greater for the digital level than the goniometer (systematic error), the two methods cannot be used interchangeably. On the basis of the average intratester LOA for the goniometer and the digital level, a change of 6-11 degrees is needed to be certain that true change has occurred. For comparison of measures made by two different therapists, a change is of 15 degrees is required to be certain a true change has occurred. A digital level can be used to reliably measure shoulder ROM but should not be used interchangeably with a standard goniometer.

Effect of knee flexion angle on Achilles tendon force and ankle joint plantarflexion moment during passive dorsiflexion

Early mobilization exercises are advocated following Achilles tendon (AT) repair, but forces on the repair during passive range of motion are unknown. The extent to which these forces change with flexion of the knee is also not known. Estimated AT forces were measured using 3 models: cadaveric, uninjured subjects, and in both legs of subjects 6 weeks following unilateral AT repair. For cadaveric testing, estimated AT force was recorded using a force transducer while cycling the ankle from 10 degrees plantarflexion to maximum dorsiflexion at 3 different knee flexion angles (0 degrees , 45 degrees , and 90 degrees ). For in vivo testing, subjects were seated in an isokinetic dynamometer, and their ankles passively cycled from plantarflexion to dorsiflexion with the knee extended and flexed 50 degrees . Passive plantarflexion moment recorded by the dynamometer was converted to AT force by estimating the AT moment arm. In the cadaveric model, knee flexion reduced estimated AT forces during dorsiflexion by more than 40% (P < .036). In vivo testing showed that estimated AT force was reduced in knee flexion in healthy subjects (P < .001) and in the uninvolved leg AT repair subjects (P = .021), but not in the AT repaired leg (P = .387). Normal AT showed a marked reduction in estimated AT force with knee flexion which was not present in repaired AT. This could be because of elongation of the repair, causing more slack in the tendon that would need to be taken up before force transmission occurs. ACFAS Level of Clinical Evidence: 4.

Clinical outcomes of coracoclavicular ligament reconstructions using tendon grafts

BACKGROUND

Numerous techniques for reconstruction of the coracoclavicular ligaments have been developed to treat acromioclavicular joint separations. A new, stronger method to reconstruct the coracoclavicular ligaments using semitendinosus tendon allografts has been previously described. No outcome studies have been published on this new procedure.

HYPOTHESIS

Reconstruction of the coracoclavicular ligaments using tendon grafts produces excellent functional results.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Nine patients underwent coracoclavicular ligament reconstruction using augmented cadaveric semitendinosus tendon allografts after a grade V acromioclavicular separation. All patients were evaluated for range of motion, strength, closed kinetic chain testing, the American Shoulder and Elbow Surgeons Rating Scale, Pennsylvania Shoulder Score, the Simple Shoulder Test, and the Acromioclavicular Joint Separation Questionnaire. Preoperative and postoperative radiographs were compared.

RESULTS

Range of motion measurements were normal in all motions except a loss of 5 degrees +/- 4 degrees (P < .05) in extension. No significant strength deficits were found. Functional closed kinetic chain tests scored comparatively to standardized norms. American Shoulder and Elbow Surgeons Rating scores were 96 +/- 5 out of 100; the Pennsylvania Shoulder Scale scores were 97 +/- 3 out of 100; the Simple Shoulder Test scores were 11.6 +/- 0 out of 12; and Acromioclavicular Joint Separation Questionnaire scores were 28 +/- 3 out of 31. Subjects reported an overall subjective satisfaction of 89% +/- 7%. Postoperative radiographs showed no loss of reduction of the acromioclavicular joint in any patient.

CONCLUSION

Outcome for coracoclavicular ligament reconstructions using augmented semitendinosus tendon grafts was excellent with full recovery of strength, minimal range of motion loss, and no clinical or radiographic loss of reduction of the acromioclavicular joint.

CLINICAL RELEVANCE

This procedure provides an excellent treatment for grade V acromioclavicular separations.

The effectiveness of a balance training intervention in reducing the incidence of noncontact ankle sprains in high school football players

BACKGROUND

A high body mass index and previous ankle sprains have been shown to increase the risk of sustaining noncontact inversion ankle sprains in high school football players.

HYPOTHESIS

Stability pad balance training reduces the incidence of noncontact inversion ankle sprains in football players with increased risk.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Height, body mass, history of previous ankle sprains, and current ankle brace/tape use were documented at the beginning of preseason training in 2 high school varsity football teams for 3 consecutive years (175 player-seasons). Players were categorized as minimal risk, low risk, moderate risk, and high risk based on the history of previous ankle sprain and body mass index. Players in the low-, moderate-, and high-risk groups (ie, any player with a high body mass index and/or a previous ankle sprain) were placed on a balance training intervention on a foam stability pad. Players balanced for 5 minutes on each leg, 5 days per week, for 4 weeks in preseason and twice per week during the season. Postintervention injury incidence was compared with preintervention incidence (107 players-seasons) for players with increased risk.

RESULTS

Injury incidence for players with increased risk was 2.2 injuries per 1000 exposures (95% confidence interval, 1.1-3.8) before the intervention and 0.5 (95% confidence interval, 0.2-1.3) after the intervention (P < .01). This represents a 77% reduction in injury incidence (95% confidence interval, 31%-92%).

CONCLUSION

The increased risk of a noncontact inversion ankle sprain associated with a high body mass index and a previous ankle sprain was eliminated by the balance training intervention.

Shoulder musculature activity and stabilization during upper extremity weight-bearing activities

BACKGROUND

Upper extremity weight-bearing exercises are routinely used in physical therapy for patients with shoulder pathology. However, little evidence exists regarding the demand on the shoulder musculature.

OBJECTIVE

To examine changes in shoulder muscle activity and center of pressure during upper extremity weight-bearing exercises of increasing difficulty.

METHODS

Electromyographic (EMG) and kinetic data were recorded from both shoulders of 15 healthy subjects (10 male and 5 female). Participants were tested in a modified tripod position under three conditions of increasing difficulty: (1) hand directly on the force plate, (2) on a green Stability Trainer(™) and (3) on a blue Stability Trainer(™). Ground reaction forces were recorded for each trial. Surface EMG was recorded from the serratus anterior, pectoralis major, upper trapezius, lower trapezius, infraspinatus, anterior deltoid, posterior deltoid, and the lateral head of the triceps muscles.

RESULTS

Mean deviation from center of pressure significantly increased when using the Stability Trainer(™) pads. The activities of the triceps, serratus anterior, and anterior deltoid muscles significantly increased as each trial progressed, irrespective of stability condition. Additionally, activity in the anterior deltoid, lower trapezius, and serratus anterior muscles significantly decreased with increasing difficulty, whereas activity in the triceps muscles significantly increased.

DISCUSSION AND CONCLUSION

Balancing on a foam pad made it more difficult to maintain the upper extremity in a stable position. However, this activity did not alter the proprioceptive stimulus enough to elicit an increase in shoulder muscle activation. While the results on this study support the use of different level Stability Trainers(™) to facilitate neuromuscular re-education, a less compliant unstable surface may produce larger training effects.

Concentric and Eccentric Muscle Fatigue of the Shoulder Rotators

Previous research has demonstrated fatigue resistance for eccentric compared with concentric muscle contractions in the lower extremity. The purpose of this study was to determine if eccentric fatigue resistance was also evident in the internal and external rotators of the shoulder. Ten subjects performed three sets of 32 maximum isokinetic contractions in shoulder internal and external rotation at 120 degrees /s. One arm performed eccentric contractions and the contralateral arm performed concentric contractions. Subjects were also tested for isometric strength prior to and immediately following the isokinetic contractions. Percent change in isokinetic torque (first five repetitions versus last five for each set) and isometric torque was compared between the arms performing eccentric and concentric contractions. Fatigue with isokinetic contractions was not different between eccentric and concentric internal rotation (25 % vs. 26 %, p = 0.76) and external rotation (24 % vs. 32 %, p = 0.11). Similarly, fatigue with isometric contractions was not different between eccentric and concentric internal rotation (11 % vs. 5 %. p = 0.33) and external rotation (15 % vs. 7 %, p = 0.07). These results indicate that unlike previously described fatigue resistance for eccentric muscle contractions in the quadriceps, dorsiflexors and plantarflexors, fatigue was not different between eccentric and concentric muscle contractions of the internal and external rotators of the shoulder.

Weakness in end-range plantar flexion after Achilles tendon repair

BACKGROUND

Separation of tendon ends after Achilles tendon repair may affect the tendon repair process and lead to postoperative end-range plantarflexion weakness.

HYPOTHESIS

Patients will have disproportionate end-range plantarflexion weakness after Achilles tendon repair.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Four-strand core suture repairs of Achilles tendon were performed on 1 female and 19 male patients. Postoperatively, patients were nonweightbearing with the ankle immobilized for 4 weeks. Plantarflexion torque, dorsiflexion range of motion, passive joint stiffness, toe walking, and standing single-legged heel rise (on an incline, decline, and level surface) were assessed after surgery (mean, 1.8 years postoperative; range, 6 months-9 years). Maximum isometric plantarflexion torque was measured at 20 degrees and 10 degrees of dorsiflexion, neutral, and 10 degrees and 20 degrees of plantar flexion. Percentage strength deficit (relative to noninvolved leg) was computed at each angle. Passive dorsiflexion range of motion was measured goniometrically. Passive joint stiffness was computed from increase in passive torque between 10 degrees and 20 degrees of dorsiflexion, before isometric contractions.

RESULTS

Significant plantarflexion weakness was evident on the involved side at 20 degrees and 10 degrees of plantar flexion (34% and 20% deficits, respectively; P <.001), with no torque deficits evident at other angles (6% at neutral, 3% at 10 degrees of dorsiflexion, 0% at 20 degrees of dorsiflexion). Dorsiflexion range of motion was not different between involved and noninvolved sides (P = .7). Passive joint stiffness was 34% lower on the involved side (P <.01). All patients could perform an incline heel rise; 14 patients could not perform a decline heel rise (P <.01).

CONCLUSION

Disproportionate weakness in end-range plantar flexion, decreased passive stiffness in dorsiflexion, and inability to perform a decline heel rise are evident after Achilles tendon repair. Possible causes include anatomical lengthening, increased tendon compliance, and insufficient rehabilitation after Achilles tendon repair.

CLINICAL RELEVANCE

Impairments will have functional implications for activities (eg, descending stairs and landing from a jump). Weakness in end-range plantar flexion may be an unrecognized problem after Achilles tendon repair.

The role of hip muscle function in the treatment of patellofemoral pain syndrome

BACKGROUND

Previous literature has associated hip weakness with patellofemoral pain syndrome.

HYPOTHESIS

Improvements in hip strength and flexibility are associated with a decrease in patellofemoral pain.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Thirty-five patients with patellofemoral pain syndrome, aged 33 +mn; 16 years (29 women, 6 men; 43 knees), were evaluated and placed on a 6-week treatment program. Hip flexion, abduction, and adduction strengths, Thomas and Ober test results, and visual analog scale scores for pain with activities of daily living as well as with exercise were documented on initial evaluation and again 6 weeks later. Treatment consisted of strength and flexibility exercises primarily focusing on the hip.

RESULTS

Hip flexion strength improved by 35% +/- 8.4% in 26 lower extremities treated successfully, compared with -1.8% +/- 3.5% in 17 lower extremities with an unsuccessful outcome (P < .001). Before treatment, there were positive Ober test results in 39 of 43 lower extremities; positive Thomas test results were seen in 31 of 43 lower extremities. A successful outcome with a concurrent normalized Ober test result was seen in 83% (20/24) of lower extremities, and successful outcomes with normalized Thomas test results were seen in 80% (16/20) of lower extremities. A combination of improved hip flexion strength (> 20%) as well as normal Ober and Thomas test results was seen in 93% of successfully treated cases (14/15 lower extremities), compared with 0% success (0/5 lower extremities) if there was no change in hip flexion strength (< 20%) and if Ober and Thomas test results remained positive.

CONCLUSIONS

Improvements in hip flexion strength combined with increased iliotibial band and iliopsoas flexibility were associated with excellent results in patients with patellofemoral pain syndrome.

Risk factors for noncontact ankle sprains in high school athletes: the role of hip strength and balance ability

BACKGROUND

Ankle sprains are among the most common sports injuries.

HYPOTHESIS

Poor balance as measured on a balance board and weakness in hip abduction strength are associated with an increased risk of noncontact ankle sprains in high school athletes.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

One hundred sixty-nine high school athletes (101 male athletes, 68 female athletes) from football, men's basketball, men's soccer, women's gymnastics, women's basketball, and women's soccer were observed for 2 years. Balance in single-limb stance on an instrumented tilt board and hip flexion, abduction, and adduction strength (handheld dynamometer) were assessed in the preseason. Body mass, height, generalized ligamentous laxity, previous ankle sprains, and ankle tape or brace use were also documented.

RESULTS

There were 20 noncontact inversion ankle sprains. Balance ability (P = .72), hip abduction strength (P = .66), hip adduction strength (P = .41), and hip flexion strength (P = .87) were not significant risk factors for ankle sprains. The incidence of grade II and grade III sprains was higher in athletes with a history of a previous ankle sprain (1.12 vs 0.26 per 1000 exposures, P < .05). A higher body mass index in male athletes was associated with increased risk (P < .05). The combination of a previous injury and being overweight further increased risk (P < .01).

CONCLUSION

Balance as measured on a balance board and hip strength were not significant indicators for noncontact ankle sprains. The apparent high injury risk associated with the combination of a history of a previous ankle sprain and being overweight in male athletes warrants further examination.

Risk factors for noncontact ankle sprains in high school football players: the role of previous ankle sprains and body mass index

BACKGROUND

In a previous study, we noted a possible connection between an athlete's weight and risk of ankle sprain.

HYPOTHESIS

A high body mass index and a history of a previous ankle sprain increase the risk of a subsequent noncontact sprain.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

One hundred fifty-two athletes from 4 football teams were observed (2 varsity and 2 junior varsity). Two teams were observed for 3 seasons, and 2 teams were observed for 1 season. Before each season, body mass, height, history of previous ankle sprains, and ankle tape or brace use were recorded.

RESULTS

There were 24 ankle sprains, of which 15 were noncontact inversion sprains (11 grade I, 3 grade II, 1 grade III; incidence, 1.08 per 1000 athlete-exposures). Injury incidence was higher in athletes with previous ankle injuries (2.60 vs 0.39; P < .001). Body mass index was also a risk factor (P < .05): injury incidence was 0.52 for players with a normal body mass index, 1.05 for players at risk of overweight, and 2.03 for overweight players. Injury incidence was 0.22 for normal-weight players with no previous ankle sprain compared with 4.27 for overweight players who had a previous sprain.

CONCLUSION

An overweight player who had a previous ankle sprain was 19 times more likely to sustain a noncontact ankle sprain than was a normal-weight player with no previous ankle sprain.

CLINICAL RELEVANCE

Ankle sprain prevention strategies should be targeted at football players with a high body mass index and a history of previous ankle sprains.

Upper and lower extremity muscle fatigue after a baseball pitching performance

BACKGROUND

Previous studies have estimated joint torques and electromyogram activity associated with the pitching motion. Although previous studies have investigated the influence of extended pitching (fatigue) on kinematic and kinetic parameters, no attempts have been made to quantify the fatigue associated with a pitching performance.

PURPOSE

Considering previous investigations on muscle activity during pitching, this study investigated muscle fatigue in upper and lower extremity muscle groups after a pitching performance.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Thirteen baseball pitchers from 4 universities and 1 independent minor league team were tested before and after 19 games. Pitchers threw an average of 99 pitches during an average of 7 innings. Shoulder, scapular, and lower extremity muscle strengths were assessed using a handheld dynamometer before and after the pitching performances.

RESULTS

Baseline strength tests revealed that the pitching arm was 12% weaker (P=.02) in the empty can test (supraspinatus) compared to the contralateral side. Postgame shoulder strength tests revealed selective fatigue of 15% in shoulder flexion (P=.02), 18% fatigue in internal rotation (P=.03), and 11% fatigue in shoulder adduction (P = .01). Minimal fatigue was noted in the empty can test, scapular stabilizers, and hip musculature.

CONCLUSIONS

A trend toward significant baseline strength in internal rotation together with significant selective postgame fatigue on internal rotation of the dominant upper extremity indicate that the internal rotators experience a high performance demand during pitching. Weakness in the empty can test on the dominant arm combined with minimal postgame fatigue was surprising given that studies and injury patterns have indicated a high performance demand on the supraspinatus during pitching.

A prospectively randomized double-blind study on the effect of initial graft tension on knee stability after anterior cruciate ligament reconstruction

BACKGROUND

No consensus exists on the amount of tension that should be applied to anterior cruciate ligament grafts to best facilitate graft incorporation and re-create normal knee mechanics.

HYPOTHESIS

Differences in initial graft tension will affect postoperative knee stability.

STUDY DESIGN

Prospective, randomized, double-blind clinical trial.

METHODS

Forty-nine patients undergoing bone-patellar tendon-bone autograft anterior cruciate ligament reconstruction by a single surgeon were randomized into high-tension (n = 27) and low-tension (n = 22) groups. Grafts were set at 90 N or 45 N. Arthrometric measurements (KT-1000 arthrometer manual maximum) of anterior tibial displacement and knee range of motion were made before surgery and at 1 week and an average of 20 months after surgery. Knee outcome scores were collected before and after surgery, and a single-leg hop test was also performed at final follow-up.

RESULTS

After anterior cruciate ligament reconstruction, anterior tibial displacement was significantly greater in the patients in the low-tension group (P < .05). The side-to-side difference in anterior tibial displacement in the high-tension and low-tension groups was 1.1 +/- 1.7 mm versus 2.4 +/- 2.4 mm 1 week after surgery and 2.2 +/- 1.6 mm versus 3.0 +/- 2.2 mm at follow-up. Five patients had abnormal anterior tibial displacement (>5 mm side-to-side difference), and all were in the low-tension group (P <.05). Knee outcome scores improved with surgery (P <.01), with similar results for low-tension and high-tension groups. Hop test deficits were not different between groups.

CONCLUSIONS

Initial graft tension affects the restoration of knee stability. A graft tension of 45 N was not sufficient for restoring knee stability.

The effect of creatine supplementation on strength recovery after anterior cruciate ligament (ACL) reconstruction: a randomized, placebo-controlled, double-blind trial

BACKGROUND

Creatine supplementation has been shown to augment training-induced strength gains. The purpose of this study was to examine the effect of creatine supplementation on recovery of muscle strength after anterior cruciate ligament (ACL) reconstruction.

HYPOTHESIS

Creatine supplementation will facilitate strength gains after ACL reconstruction.

STUDY DESIGN

Double-blind, prospective, and randomized clinical trial.

METHODS

Sixty patients were randomized into creatine or placebo groups. Quadriceps and hamstring strength and power were measured isokinetically. Hip flexor, abductor, and adductor strengths were measured with a handheld dynamometer prior to surgery and at 6 weeks, 12 weeks, or 6 months after surgery.

RESULTS

From 6 weeks to 12 weeks after surgery, there were significant increases in strength on the involved side for knee extension (47%), knee flexion (27%), hip flexion (20%), hip abduction (9%), and hip adduction (17%). These strength improvements were unaffected by creatine supplementation with similar effects in the creatine and placebo groups. From 6 weeks to 12 weeks after surgery, there were significant increases in power on the involved side for knee extension (46%) and knee flexion (26%), but these effects were not affected by creatine supplementation. At 6 months, creatine supplementation did not affect outcome as measured by the single leg hop test for distance or the knee outcome score.

CONCLUSIONS

The results demonstrate that patients do not benefit from creatine supplementation during the first 12 weeks of rehabilitation after ACL reconstruction.