Quadriceps and Patient-Reported Function in ACL-Reconstructed Patients: A Principal Component Analysis.

CONTEXT: Assessment of physical function for individuals after anterior cruciate ligament reconstruction (ACL-R) is complex and warrants the use of diverse evaluation strategies. To maximize the efficiency of assessment, there is a need to identify tests that provide the most meaningful information about this population. OBJECTIVE: To investigate underlying constructs of quadriceps muscle function that uniquely describe aspects of performance in patients after ACL-R and establish clinical thresholds for measures able to classify patients with and without ACL-R. DESIGN: Cross-sectional. SETTING: Research laboratory. Patients (or Other Participants): Seventy-two patients with a primary, unilateral ACL-R (32 males and 40 females, age = 26.0 [9.3] y, time since surgery = 46.5 [58.0] mo) and 30 healthy controls (12 males and 18 females, age = 22.7 [4.6] y). INTERVENTION(S): Quadriceps function was assessed bilaterally during 1 study visit. MAIN OUTCOME MEASURES: Isokinetic strength (peak torque, total work, and average power) at 90° and 180°/s, maximal voluntary isometric contraction torque, fatigue index, central activation ratio, Hoffmann reflex, and active motor threshold. Principal component analyses were performed for the involved limb, contralateral limb, and limb symmetry. Receiver-operator characteristic curve analyses were conducted to determine the diagnostic utility of each variable. Binary logistic regression was used to predict group membership (ACL-R vs healthy). RESULTS: Three components of peripheral, central, and combined (peripheral and central) muscle function were identified, explaining 70.7% to 80.5% of variance among measures of quadriceps function. Total knee-extensor work at 90°/s (≥18.4 J/kg), active motor threshold (≥39.5%), and central activation ratio (≥94.7%) of the involved limb were strong predictors of patient status and correctly classified 83.5% of patients with ACL-R (P < .001). CONCLUSIONS: Unique constructs of peripheral, central, and combined muscle function exist in patients with ACL-R. Total knee-extensor work at 90°/s, active motor threshold, and central activation ratio consistently explained a significant portion of variance in measures of quadriceps function, demonstrated acceptable to excellent diagnostic utility, and predicted group membership with 72.8% to 83.5% accuracy.

Differential rates of recovery after acute sport-related concussion: electrophysiologic, symptomatic, and neurocognitive indices.

PURPOSE: To determine if motor evoked potentials (MEPs), postconcussion signs and symptoms, and neurocognitive functions follow a similar recovery pattern after concussion. METHODS: Nine collegiate athletes with acute concussion (>24 hours after injury) participated in this retrospective time series design. Transcranial magnetic stimulation was applied over the motor cortex, and MEPs were recorded from the contralateral upper extremity. Self-reported symptoms were evaluated using the Head Injury Scale, and the Concussion Resolution Index was used to assess neurocognitive function. All measures were repeated on days 3, 5, and 10 after injury. RESULTS: Composite scores on the Head Injury Scale were significantly higher on day 1 after injury (F3,51 = 15.3; P = 0.0001). Processing speed on the Concussion Resolution Index was slower on days 1, 3, and 5 compared with that on day 10 (F3,24 = 6.75; P = 0.0002). Median MEP latencies were significantly longer on day 10 compared with day 1 after concussion (t8 = -2.69; P = 0.03). Ulnar MEP amplitudes were significantly smaller on day 3 after concussion compared with day 5 (t8 = -3.48; P = 0.008). CONCLUSIONS: Acutely concussed collegiate athletes demonstrate changes in MEPs, which persist for up to 10 days after injury and do not follow the same recovery pattern as symptoms and neuropsychological test performance. The apparent differential rates of recovery most likely indicate different pathophysiological processes occurring in the immediate postconcussion period.

Knee-extension exercise's lack of immediate effect on maximal voluntary quadriceps torque and activation in individuals with anterior knee pain.

CONTEXT: Weight-bearing (WB) and non-weight-bearing (NWB) exercises are commonly used in rehabilitation programs for patients with anterior knee pain (AKP). OBJECTIVE: To determine the immediate effects of isolated WB or NWB knee-extension exercises on quadriceps torque output and activation in individuals with AKP. DESIGN: A single-blind randomized controlled trial. SETTING: Laboratory. PARTICIPANTS: 30 subjects with self-reported AKP. INTERVENTIONS: Subjects performed a maximal voluntary isometric contraction (MVIC) of the quadriceps (knee at 90°). Maximal voluntary quadriceps activation was quantified using the central activation ratio (CAR): CAR = MVIC/(MVIC + superimposed burst torque). After baseline testing, subjects were randomized to 1 of 3 intervention groups: WB knee extension, NWB knee extension, or control. WB knee-extension exercise was performed as a sling-based exercise, and NWB knee-extension exercise was performed on the Biodex dynamometer. Exercises were performed in 3 sets of 5 repetitions at approximately 55% MVIC. Measurements were obtained at 4 times: baseline and immediately and 15 and 30 min postexercise. MAIN OUTCOME MEASURES: Quadriceps torque output (MVIC: N·m/Kg) and quadriceps activation (CAR). RESULTS: No significant differences in the maximal voluntary quadriceps torque output (F2,27 = 0.592, P = .56) or activation (F2,27 = 0.069, P = .93) were observed among the 3 treatment groups. CONCLUSIONS: WB and NWB knee-extension exercises did not acutely change quadriceps torque output or activation. It may be necessary to perform exercises over a number of sessions and incorporate other disinhibitory interventions (eg, cryotherapy) to observe acute changes in quadriceps torque and activation.

The effectiveness of traditional and sling exercise strength training in women.

Strength training often combines closed-kinetic-chain exercises (CKCEs) and open kinetic-chain exercises (OKCEs). The CKCE may be more effective for improving performance in lower-body training. Recently, we reported upper-body CKCE (using a commercially available system of ropes and slings, Redcord AS, Staubo, Norway) was as effective as OKCE training for strength gains and that CKCE was more effective than OKCE for improving throwing performance. To our knowledge the effectiveness of a strength training program that uses exclusively CKCE is unknown. In this study, we examined the effectiveness of CKCE vs. OKCE strength training programs in women enrolled in an introductory strength training program. Twenty-six participants were randomized to OKCE (traditional exercises) or CKCE (sling-based exercises). Participants completed 6 sets per week for 13 weeks. Pre and posttraining evaluations included the following: 1 repetition maximum (1RM) leg and bench press; sling exercise push-ups; isokinetic dynamometry; lateral step-down test; and the Star Excursion Balance Test. Both groups significantly improved bench press (by an average of 4-6 kg) and leg press (by an average of 23-35 kg) (p < 0.001). There was a significant group × time interaction (p < 0.001) for sling exercise push-ups (OKCE pre = 5.5 ± 8.6, OKCE post = 6.1 ± 8.2, CKCE pre = 6.8 ± 6.0, CKCE post = 16.9 ± 6.6). Isokinetic measures of knee extension, knee flexion, shoulder internal rotation, and shoulder external rotation increased (improvements ranged from 2.7 to 27.7%), with no group differences. Both OKCE and CKCE strength training elicited similar changes in balance. We conclude that CKCE training is equally as effective as OKCE training during the initial phases of a strength training program in women. The fact that only CKCE improved sling exercise push-ups supports previous findings suggesting functional superiority of CKCE.

A preliminary investigation of motor evoked potential abnormalities following sport-related concussion.

BACKGROUND: Assessment of concussion is primarily based on self-reported symptoms, neurological examination and neuropsychological testing. The neurophysiologic sequelae and the integrity of the corticomotor pathways could be obtained by evaluating motor evoked potentials (MEPs). OBJECTIVES: To compare MEPs obtained through transcranial magnetic stimulation (TMS) in acutely concussed and non-concussed collegiate athletes. METHODS: Eighteen collegiate athletes (12 males, six females, aged 20.4 +/- 1.3 years) including nine subjects with acute concussion ( 0.05). CONCLUSION: MEP abnormalities among acutely concussed collegiate athletes provide direct electrophysiologic evidence for the immediate effects of concussion.

Anterior shoulder laxity is not correlated with medial elbow laxity in high school baseball players.

CONTEXT: Uninjured baseball players have been shown to have increased anterior glenohumeral joint laxity, which may result in adaptive changes at the medial elbow. OBJECTIVE: To determine the relationship between anterior shoulder laxity and medial elbow laxity in both arms of baseball and nonbaseball high school athletes and compare the laxity of dominant and nondominant shoulders and elbows of high school baseball and nonbaseball players. DESIGN: Cohort design. SETTING: Local high schools. PARTICIPANTS: Thirty healthy high school male athletes. OUTCOME MEASURES: Anterior shoulder and medial elbow laxity measurements were taken bilaterally with the Ligmaster. RESULTS: Dominant and nondominant shoulder laxity was significantly greater in the nonbaseball players than the baseball players. No other significant relationships existed. CONCLUSIONS: High school baseball players exhibit less anterior shoulder laxity than do nonbaseball players. No relationship exists between anterior shoulder and medial elbow laxity in high school baseball players.

The effect of protective equipment on cervical spine alignment in collegiate lacrosse players.

BACKGROUND: Contact sports place athletes at risk for cervical spine injury. Protective helmets and shoulder pads worn by football and ice hockey athletes alter cervical spine alignment. The effect of helmet and shoulder pads on neck alignment in lacrosse athletes is not known. HYPOTHESIS: Helmets and shoulder pads worn by lacrosse athletes alter cervical spine alignment. STUDY DESIGN: Controlled laboratory study. METHODS: Sagittal plane cervical spine alignment was evaluated in 16 uninjured male collegiate lacrosse players using computed tomography. Patients were immobilized in the supine position on a standard spine board. Testing was performed without equipment, with both helmet and shoulder pads in place, and with the helmet removed. Angular measurements of the cervical spine were made and analyzed. RESULTS: The presence of both the helmet and shoulder pads caused an increase in overall cervical extension (mean, 6 degrees ) compared with the absence of both pieces of equipment (P = .002). Helmet removal alone resulted in a mean increase in cervical flexion of 4.7 degrees in the upper cervical spine compared with the presence of both pieces of equipment (P = .011). Compared with the absence of equipment, shoulder pads caused increased cervical flexion in the lower cervical spine (mean, 4.4 degrees ; P = .036). CONCLUSION: Protective equipment worn by lacrosse athletes causes statistically significant increases in cervical extension, and its removal causes statistically significant increases in cervical flexion. This alteration is different from that previously reported for protective equipment in football and ice hockey. CLINICAL RELEVANCE: The authors' recommendation is that both lacrosse helmets and shoulder pads be left in place until they can be completely removed in a controlled fashion. The effect of external equipment on neck position is different for lacrosse compared with football and ice hockey.