Context: Transcranial magnetic stimulation (TMS) may provide important information regarding the corticospinal mechanisms that may contribute to the neuromuscular activation impairments. Paired-pulse TMS testing is a reliable method for measuring intracortical facilitation and inhibition; however, little evidence exists regarding agreement of these measures in the quadriceps. Objective: To determine the between-sessions and interrater agreement of intracortical excitability (short- and long-interval intracortical inhibition [SICI, LICI] and intracortical facilitation [ICF]) in the dominant-limb quadriceps. Design: Reliability study. Setting: Research laboratory. Participants: 13 healthy volunteers (n = 6 women; age 24.7 ± 2.1 y; height 1.7 ± 0.1 m; mass 77.1 ± 17.4 kg). Intervention: Participants completed 2 TMS sessions separated by 1 wk. Main Outcome Measures: Two investigators measured quadriceps SICI, LICI, and ICF at rest and actively (5% of maximal voluntary isometric contraction). All participants were seated in a dynamometer with the knee flexed to 90°. Intracortical-excitability paradigm and investigator order were randomized. Bland-Altman analyses were used to establish agreement. Results: Agreement was stronger between sessions within a single investigator than between investigators and for active than resting measures. Agreement was strongest for resting SICI and active ICF and LICI between sessions for each investigator. Conclusions: Quadriceps intracortical excitability may be measured longitudinally by a single investigator, though active muscle contraction should be elicited during testing.
Abbey C. Thomas, Brian G. Pietrosimone, and Carter J. Bayer
Shelby Waldron, J.D. DeFreese, Brian Pietrosimone, Johna Register-Mihalik, and Nikki Barczak
Sport specialization has been linked to multiple negative health related outcomes including increased injury risk and sport attrition, yet a gap remains in our understanding of potential psychological outcomes of early specialization (≤ age 12). The current study evaluated the associations between retrospective athlete reports of sport specialization and both retroactive and current psychological health outcomes. Early specializers reported significantly higher levels of multiple maladaptive psychological outcomes (e.g., global athlete burnout, emotional and physical exhaustion, sport devaluation, amotivation). Overall, findings suggest that specialization environment factors, in addition to the age of specialization, are potentially critical factors in determining health and well-being outcomes. Findings support prominent position statements suggesting early specialization may be associated with increased health risks. Study findings may also inform the development of guidelines and recommendations to aid parents, coaches, and athletes in positively impacting athlete psychosocial outcomes.
Matthew Harkey, Michelle McLeod, Ashley Van Scoit, Masafumi Terada, Michael Tevald, Phillip Gribble, and Brian Pietrosimone
Altered neuromuscular function and decreased dorsiflexion range of motion (DFROM) have been observed in patients with chronic ankle instability (CAI). Joint mobilizations are indicated for restoring DFROM and dynamic postural control, yet it remains unknown if a mobilization can alter neuromuscular excitability in muscles surrounding the ankle.
To determine the immediate effects of a Maitland grade III anterior-to-posterior joint mobilization on spinal-reflex and corticospinal excitability in the fibularis longus (FL) and soleus (SOL), DFROM, and dynamic postural control.
Single-blinded randomized control trial.
30 patients with CAI randomized into a mobilization (n = 15) or control (n = 15) group.
Maitland grade III anterior-to-posterior joint mobilization.
Main Outcome Measures:
Spinal-reflex excitability was measured with the Hoffmann reflex, while corticospinal excitability was evaluated with transcranial magnetic stimulation. DFROM was measured seated with the knee extended, and dynamic postural control was quantified with the Star Excursion Balance Test. Separate 2 × 2 repeated-measures ANOVAs were performed for each outcome measure. Dependent t tests were used to evaluate individual differences within groups in the presence of significance.
Spinal-reflex and corticospinal excitability of the SOL and FL were not altered in the mobilization or control group (P > .05). DFROM increased immediately after the mobilization (P = .05) but not in the control group, while dynamic postural control was unchanged in both groups (P > .05).
A single joint-mobilization treatment was efficacious at restoring DFROM in participants with CAI; however, excitability of spinal reflex and corticospinal pathways at the ankle and dynamic postural control were unaffected.
Michelle M. McLeod, Phillip Gribble, Kate R. Pfile, and Brian G. Pietrosimone
Arthroscopic partial meniscectomy (APM) after meniscal tear has been widely accepted and associated with quick return to activity. Unfortunately, meniscectomy is associated with risk for knee osteoarthritis, which may be attributed to postsurgical quadriceps weakness. This has important implications, as the quadriceps play a prominent role in knee stabilization and energy attenuation in the lower extremity.
To determine the magnitude of interlimb quadriceps strength deficits in people with unilateral APM by systematically reviewing the current literature.
The Web of Knowledge databases were searched on September 22, 2010, using terms meniscus OR meniscectomy AND quadriceps strength OR quadriceps weakness. Included articles were written in English, reporting means and SDs of isokinetic peak torque at 60° and 180°/s for both limbs.
Four articles were included in the final analysis. Effect sizes and 95% confidence intervals (CI) were calculated between limbs for periods less than 1 mo, 1–3 mo, 3–6 mo, and more than 6 mo.
Homogeneous effect sizes indicate quadriceps weakness in the involved limb. Effects were strong at less than 1 mo (d = −1.01 to −1.62), while weak to strong effects were found for 1–3 mo (d = −0.40 to −8.04) and 3–6 mo (d = −0.40 to −5.11). Weak effects were found at more than 6 mo (d = −0.30 to −0.37). Definitive effects with a CI not crossing zero were found in 65% of the data. Although APM patients return to function within weeks after surgery, prolonged quadriceps strength deficits may increase the risk of knee-joint degeneration. Furthermore, evidence of bilateral dysfunction after unilateral injury may suggest that neuromuscular deficits post-APM are greater than the interlimb differences found in this review. Further research should be conducted to determine the nature of strength deficits and the best methods for restoring strength after APM.
Masafumi Terada, Megan Beard, Sara Carey, Kate Pfile, Brian Pietrosimone, Elizabeth Rullestad, Heather Whitaker, and Phillip Gribble
This study aimed to compare time-to-boundary and sample entropy during a single-leg balance task between individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls. Twenty-two participants with CAI, 20 lateral ankle sprain copers, and 24 healthy controls performed a single-leg balance task during an eyes-closed condition. Participants with CAI exhibited lower time-to-boundary values compared with lateral ankle sprain copers and healthy controls. However, we did not find differences in sample entropy variables between cohorts. A decrease in time-to-boundary values in participants with CAI indicated that CAI may constrain the ability of the sensorimotor system to maintain the center of pressure within the boundaries of the base of support. However, the regularity of the center of pressure velocity time series appears not to be altered in the CAI cohort in this study.
Kate R. Pfile, Phillip A. Gribble, Gretchen E. Buskirk, Sara M. Meserth, and Brian G. Pietrosimone
Epidemiological data demonstrate the need for lower-extremity injury-prevention training. Neuromuscularcontrol (NMC) programs are immediately effective at minimizing lower-extremity injury risk and improving sport-related performance measures. Research investigating lasting effects after an injury-prevention program is limited.
To determine whether dynamic balance, landing mechanics, and hamstring and quadriceps strength could be improved after a 6-wk NMC intervention and maintained for a season.
Prospective case series.
11 Division I women’s basketball players (age 19.40 ± 1.35 y, height 178.05 ± 7.52 cm, mass 72.86 ± 10.70 kg).
Subjects underwent testing 3 times, completing the Star Excursion Balance Test (SEBT), Landing Error Scoring System (LESS), and isometric strength testing for the hamstrings and quadriceps muscles. Pretest and posttest 1 occurred immediately before and after the intervention, respectively, and posttest 2 at the end of the competitive season, 9 mo after posttest 1. Subjects participated in eighteen 30-min plyometric and NMC-training sessions over a 6-wk period.
Main Outcome Measures:
The normalized SEBT composite score, normalized peak isometric hamstrings:quadriceps (H:Q) ratio, and the LESS total score.
The mean composite reach significantly improved over time (F 2,10 = 6.96, P = .005) where both posttest scores were significantly higher than pretest (70.41% ± 4.08%) (posttest 1 73.48% ± 4.19%, t 10 = –3.11, P = .011) and posttest 2 (74.2% ± 4.77%, t 10 = –3.78, P = .004). LESS scores significantly improved over time (F 2,10 = 6.29, P = .009). The pretest LESS score (7.30 ± 3.40) was higher than posttest 1 (4.9 ± 1.20, t 10 = 2.71, P = .024) and posttest 2 (5.44 ± 1.83, t 10 = 2.58, P = .030). There were no statistically significant differences (P > .05) over time for the H:Q ratio when averaging both legs (F 2,10 = 0.83, P = .45).
A 6-wk NMC program improved landing mechanics and dynamic balance over a 9-mo period in women’s basketball players. NMC adaptations can be retained without an in-season maintenance program.
Hayley M. Ericksen, Brian Pietrosimone, Phillip A. Gribble, and Abbey C. Thomas
Context: Feedback is an important factor in interventions designed to reduce anterior cruciate ligament injury risk. Self-analysis feedback requires participants to self-critique their jump-landing mechanics; however, it is unknown if individuals can effectively self-analyze their own biomechanics and if this self-analysis agrees with observed biomechanical changes by an expert. Objective: To determine agreement between an expert and participants on biomechanical errors committed during 3 of 12 sessions, which were part of an intervention to change jump-landing biomechanics in healthy females. Design: Descriptive analysis. Setting: Research laboratory. Patients or Other Participants: Healthy recreationally active females with no history of lower-extremity fracture or surgery. Interventions: Participants completed a 4-week, 12-session feedback intervention. Each intervention session lasted approximately 15 minutes and included asking participants to perform 6 sets of 6 jumps off a 30-cm-high box placed 50% of their height away from the target landing area. Participants performed self-analysis feedback and received expert feedback on 7 different jump-landing criteria following each set of jumps. Main Outcome Measures: Data were coded, and agreement between the expert and the participant was assessed using Cohen’s unweighted kappa for sessions 1, 6, and 12. Results: There was agreement between the expert and participants for 0/7 criteria for session 1, 3/7 criteria for session 6, and 4/7 criteria for session 12. Conclusions: Participants demonstrated some agreement with the expert when evaluating their jump-landing biomechanics. Self-analysis feedback may not replace what an expert can provide; both types of feedback may be better used in conjunction to produce significant biomechanical changes. Changes made by the participant may not translate into biomechanical changes during a real-life game or practice situation. Future research should continue to investigate effective interventions to reduce injury risk.
Brian G. Pietrosimone, Adam S. Lepley, Hayley M. Ericksen, Phillip A. Gribble, and Jason Levine
Disability is common in a proportion of patients after anterior cruciate ligament reconstruction (ACL-R). Neuromuscular quadriceps deficits are a hallmark impairment after ACL-R, yet the link between muscle function and disability is not understood.
To evaluate the ability of quadriceps strength and cortical excitability to predict self-reported disability in patients with ACL-R.
Fifteen participants with a history of ACL-R (11 female, 4 male; 172 ± 9.8 cm, 70.4 ± 17.5 kg, 54.4 ± 40.9 mo postsurgery) were included in this study. Corticospinal excitability was assessed using active motor thresholds (AMT), while strength was assessed with maximal voluntary isometric contractions (MVIC). Both voluntary strength and corticospinal excitability were used to predict disability measured with the International Knee Documentation Committee Index (IKDC).
The overall multiple-regression model significantly predicted 66% of the variance in self-reported disability as measured by the IKDC index (R 2 = .66, P = .01). Initial imputation of MVIC into the model accounted for 61% (R 2 = .61, P = .01) of the variance in IKDC. The subsequent addition of AMT into the model accounted for an insignificant increase of 5% (Δ R 2 = .05, P = .19) in the prediction capability of the model.
Quadriceps voluntary strength and cortical excitability predicted two-thirds of the variance in disability of patients with ACL-R, with strength accounting for virtually all of the predictive capability of the model.
Matthew Harkey, Michelle M. McLeod, Masafumi Terada, Phillip A. Gribble, and Brian G. Pietrosimone
Spinal-reflexive and corticomotor excitability may have a critical role in altering muscle function needed to stabilize the ankle in people with chronic ankle instability (CAI).
To determine the association between self-reported disability and both spinal-reflexive and corticomotor excitability in people with CAI.
Descriptive laboratory study.
30 participants with CAI.
Main Outcome Measures:
Soleus spinal-reflexive excitability was measured with normalized Hoffmann reflexes (H:M ratio), and corticomotor excitability was measured with transcranial magnetic stimulation and quantified by normalized motor-evoked-potential (MEP) amplitudes at 120% of active motor threshold (120%MEP). Self-reported disability was quantified with the activities-of-daily-living and sport subscales of the Foot and Ankle Ability Measure (FAAM-ADL and FAAM-S). Separate linear Pearson product–moment correlations and nonlinear quadratic correlations were used to determine associations between the neural-excitability and disability variables.
Thirty participants were included in the spinal-reflexive-excitability analysis, while only 19 were included in the corticomotor analysis. There was a significant, weak linear association between H:M ratio and FAAM-ADL (R = .39, P = .03) and a nonsignificant, weak linear association between H:M ratio and FAAM-S (R = .36, P = .06). There were significant, moderate quadratic associations between H:M ratio and both FAAM-ADL (R = .48, P = .03) and FAAM-S (R = .50, P = .02). There was a significant, moderate linear association between 120%MEP and FAAM-ADL (R = –.48, P = .04) and a nonsignificant, moderate negative linear association between FAAM-S (R = –.42, P = .07). There was a significant, moderate quadratic association between 120%MEP and FAAM-ADL (R = .57, P = .046) and a significant, strong quadratic correlation between 120%MEP and FAAM-S (R = .71, P = .004).
There are significant quadratic associations between self-reported disability and both spinal-reflexive and corticomotor excitability of the soleus. CAI participants with low or high neural excitability present with lower function.
Jonathan S. Goodwin, Robert A. Creighton, Brian G. Pietrosimone, Jeffery T. Spang, and J. Troy Blackburn
Context: Orthotic devices such as medial unloader knee braces and lateral heel wedges may limit cartilage loading following trauma or surgical repair. However, little is known regarding their effects on gait biomechanics in young, healthy individuals who are at risk of cartilage injury during physical activity due to greater athletic exposure compared with older adults. Objective: Determine the effect of medial unloader braces and lateral heel wedges on lower-extremity kinematics and kinetics in healthy, young adults. Design: Cross-sectional crossover design. Setting: Laboratory setting. Patients: Healthy, young adults who were recreationally active (30 min/d for 3 d/wk) between 18 and 35 years of age, who were free from orthopedic injury for at least 6 months, and with no history of lower-extremity orthopedic surgery. Interventions: All subjects completed normal over ground walking with a medial unloader brace at 2 different tension settings and a lateral heel wedge for a total of 4 separate walking conditions. Main Outcome Measures: Frontal plane knee angle at heel strike, peak varus angle, peak internal knee valgus moment, and frontal plane angular impulse were compared across conditions. Results: The medial unloader brace at 50% (−2.04° [3.53°]) and 100% (−1.80° [3.63°]) maximum load placed the knee in a significantly more valgus orientation at heel strike compared with the lateral heel wedge condition (−0.05° [2.85°]). However, this difference has minimal clinical relevance. Neither of the orthotic devices altered knee kinematics or kinetics relative to the control condition. Conclusions: Although effective in older adults and individuals with varus knee alignment, medial unloader braces and lateral heel wedges do not influence gait biomechanics in young, healthy individuals.