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.

The health status of retired American football players: Super Bowl III revisited.

Background: Despite a perception that retired professional football players have poor health, there are little supporting data.

Hypothesis: Retired football players have poor health compared with age-matched population norms.

Study Design: Cross-sectional study; Level of evidence, 4.

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.

Effect of fatigue on single-leg hop landing biomechanics.

The objective of this study was to measure adaptations in landing strategy during single-leg hops following thigh muscle fatigue. Kinetic, kinematic, and electromyographic data were recorded as thirteen healthy male subjects performed a single-leg hop in both the unfatigued and fatigued states. To sufficiently fatigue the thigh muscles, subjects performed at least two sets of 50 step-ups.

Performance demands of professional male tennis players.

Objective: To quantify the performance demands in professional male tennis.

Methods: Games from three grand slam tournaments were analysed by an elite tennis player from video recordings. Game related data were collected on 22 players (French Open, 8 (186 games); Wimbledon, 11 (206 games); US Open, 9 (224 games)).

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.

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.

Quantifying shoulder rotation weakness in patients with shoulder impingement.

The purpose of this study was to determine whether strength deficits could be detected in individuals with and without shoulder impingement, all of whom had normal shoulder strength bilaterally according to grading of manual muscle testing. Strength of the internal rotators and external rotators was tested isokinetically at 60 degrees /s and 180 degrees /s, as well as manually with a handheld dynamometer (HHD) in 17 patients and 22 control subjects. Testing was performed with the shoulder positioned in the scapular plane and in 90 degrees of shoulder abduction with 90 degrees of elbow flexion (90-90).

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.

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.

The effect of rotator cuff tear size on shoulder strength and range of motion.

Study Design: Prospective cohort study.

Objectives: To determine the effect of rotator cuff tear size on shoulder strength and range of motion.

Background: Patients with rotator cuff pathology typically present with weakness and motion loss in various motions.

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.

The role of exercising muscle length in the protective adaptation to a single bout of eccentric exercise.

The purpose of this study was to determine if the protective adaptation to a single bout of eccentric exercise (repeated bout effect) is dependent on the muscle length at which the eccentric contractions are performed. Ten subjects (six men, four women) performed two bouts of 120 isokinetic eccentric contractions separated by 2 weeks (target intensity was 90% of maximum isometric strength at 70 degrees). In the initial bout one limb exercised from 30 degrees to 70 degrees of knee flexion (short initial bout; SIB) and the contralateral limb exercised from 70 degrees to 110 degrees (long initial bout; LIB).

Transcutaneous magnetic stimulation of the quadriceps via the femoral nerve.

We investigated the efficacy of different frequencies and intensities of magnetic stimulation for activating the quadriceps muscles; a painless method for stimulating the quadriceps would be useful in the rehabilitation of patients who have difficulty in voluntarily activating their muscles after injury or surgery. Eleven subjects underwent magnetic stimulation of the femoral nerve over a range of frequencies and intensities using a MagStim Rapid magnetic stimulator. Magnetic stimulation at 30 Hz at 80% of the power output of the stimulator used was capable of generating 72% of quadriceps maximal voluntary contraction torque.

Effect of knee flexion angle on active joint stiffness.

Aim: The purpose of this study was to determine if active joint stiffness measured during maximum voluntary knee extension contractions was affected by knee flexion angle.

Methods: Eighteen subjects volunteered (11 male, seven female). A stretch was imposed on isometric knee contractions performed at 30 degrees, 50 degrees, 70 degrees, 90 degrees, and 110 degrees of knee flexion.

Changes in the relationship between joint angle and torque production associated with the repeated bout effect.

A single bout of eccentric exercise induces a protective adaptation against damage from a repeated bout. The aim of this study was to determine whether this repeated bout effect is due to a change in the length-tension relationship. Twelve individuals performed an initial bout of six sets of 10 eccentric quadriceps contractions and then performed a repeated bout 2 weeks later.

Reconstruction of the coracoclavicular ligaments with tendon grafts: a comparative biomechanical study.

Background: Numerous surgical techniques have been described to address injuries to the coracoclavicular ligaments.

Purpose: To compare the biomechanical properties of tendon graft reconstructions with those of the native coracoclavicular ligaments and various other repair methods.

Study Design: Controlled laboratory study.

Recent advances in the understanding of the repeated bout effect: the protective effect against muscle damage from a single bout of eccentric exercise.

The repeated bout effect refers to the adaptation whereby a single bout of eccentric exercise protects against muscle damage from subsequent eccentric bouts. While the mechanism for this adaptation is poorly understood there have been significant recent advances in the understanding of this phenomenon. The purpose of this review is to provide an update on previously proposed theories and address new theories that have been advanced.

Food and fluid intake and disturbances in gastrointestinal and mental function during an ultramarathon.

The purpose of this study was to document eating strategies employed by runners during a 160-km race, and to identify eating patterns that predispose the runner to disturbed mental or gastrointestinal functioning. We monitored intake in 19 volunteers during the 12 hours pre-race. Intake was determined by interview with runners approximately every 12 km throughout the race.

Food intake and electrolyte status of ultramarathoners competing in extreme heat.

Objective: To relate changes in laboratory indices to dietary intake during extremely prolonged running and to determine if dietary intake influences the ability of runners to finish an 160 km trail race.

Methods: We monitored intake and serum chemistries of 26 runners competing in an 160 km foot race in temperatures which peaked at 38 degrees C. Blood was drawn pre-, mid- and post-race.

Evidence of abnormal anteroposterior patellar tilt in patients with patellar tendinitis with use of a new radiographic measurement.

Background: A number of clinical conditions of the patellofemoral joint have been correlated with abnormal patellofemoral radiographic measurements.

Hypothesis: An abnormal anteroposterior patellar-tilt angle may be a contributing factor to pathologic conditions of the knee.

Study Design: Prospective nonrandomized clinical trial.

Electromyographic predictors of residual quadriceps muscle weakness after anterior cruciate ligament reconstruction.

Background: Despite the high prevalence of residual quadriceps muscle weakness after anterior cruciate ligament reconstruction, specific predictive factors have not been identified.

Hypothesis: Electromyographic analysis is a better predictor of residual muscle weakness than is preoperative strength.

Study Design: Prospective cohort study.

Adductor muscle strains in sport.

An in-season adductor muscle strain may be debilitating for the athlete. Furthermore, an adductor strain that is treated improperly could become chronic and career threatening. Any one of the six muscles of the adductor group could be involved.

Differences in activation patterns between eccentric and concentric quadriceps contractions.

Previous studies analysing electromyograms (EMGs) from indwelling electrodes have indicated that fast-twitch motor units are selectively recruited for low-intensity eccentric contractions. The aim of this study was to compare the frequency content of surface EMGs from quadriceps muscles during eccentric and concentric contractions at various contraction intensities. Electromyograms were recorded from the rectus femoris, vastus lateralis and vastus medialis muscles of 10 men during isokinetic (1.

Neuromuscular rehabilitation of a female Olympic ice hockey player following anterior cruciate ligament reconstruction.

Study Design: Case study.

Objective: To demonstrate the unique aspects of rehabilitating a female athlete participating in ice hockey following anterior cruciate ligament (ACL) reconstruction.

Background: The patient was a 28-year-old female who sustained a traumatic injury to her left knee while playing ice hockey.