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.
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Abbey C. Thomas, Brian G. Pietrosimone, and Carter J. Bayer
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.
Brian G. Pietrosimone, Adam S. Lepley, Hayley M. Ericksen, Phillip A. Gribble, and Jason Levine
Background:
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.
Purposes:
To evaluate the ability of quadriceps strength and cortical excitability to predict self-reported disability in patients with ACL-R.
Methods:
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).
Results:
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.
Conclusions:
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.
Michelle M. McLeod, Phillip Gribble, Kate R. Pfile, and Brian G. Pietrosimone
Context:
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.
Objective:
To determine the magnitude of interlimb quadriceps strength deficits in people with unilateral APM by systematically reviewing the current literature.
Evidence Acquisition:
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.
Evidence Synthesis:
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.
Conclusion:
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.
Kate R. Pfile, Phillip A. Gribble, Gretchen E. Buskirk, Sara M. Meserth, and Brian G. Pietrosimone
Context:
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.
Objective:
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.
Design:
Prospective case series.
Setting:
Controlled laboratory.
Participants:
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).
Interventions:
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.
Results:
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).
Conclusions:
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.
Matthew Harkey, Michelle M. McLeod, Masafumi Terada, Phillip A. Gribble, and Brian G. Pietrosimone
Context:
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).
Objective:
To determine the association between self-reported disability and both spinal-reflexive and corticomotor excitability in people with CAI.
Design:
Descriptive laboratory study.
Setting:
Research laboratory.
Participants:
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.
Results:
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).
Conclusions:
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.
Brittney A. Luc, Adam S. Lepley, Michael A. Tevald, Phillip A. Gribble, Donald B. White, and Brian G. Pietrosimone
Context:
Alterations in corticomotor excitability are observed in a variety of patient populations, including the musculature surrounding the knee and ankle after joint injury. Active motor threshold (AMT) and motor-evoked-potential (MEP) amplitudes elicited through transcranial magnetic stimulation (TMS) are outcome measures used to assess corticomotor excitability and have been deemed reliable in upper-extremity musculature. However, there are few studies assessing the reliability of TMS measures in lower-extremity musculature.
Objective:
To determine the intersession reliability of AMT and MEP amplitudes over 14 and 28 d in the quadriceps and fibularis longus (FL).
Design:
Descriptive laboratory study.
Setting:
University laboratory
Participants:
20 able-bodied volunteers (10 men, 10 women; 22.35 ± 2.3 y, 1.71 ± 0.11 m, 73.61 ± 16.77 kg).
Main Outcome Measures:
AMT and MEP amplitudes were evaluated at 95%, 100%, 105%, 110%, 120%, 130%, and 140% of AMT in the dominant and nondominant quadriceps and FL. Interclass correlation coefficients (ICCs) were used to assess reliability for absolute agreement and internal consistency between baseline and 2 follow-up sessions at 14 and 28 d postbaseline. Each ICC was fit with the best-fit straight line or parabola to smooth out noise in the observations and best determine if a pattern existed in determining the most reliable MEP value.
Results:
All muscles yielded strong ICCs between baseline and both time points for AMT. MEPs in both the quadriceps and FL produced varying degrees of reliability, with the greatest reliability demonstrated on day 28 at 130% and 140% of AMT in the quadriceps and FL, respectively. The dominant FL muscle showed a significant pattern; as TMS intensity increased, MEP reliability increased.
Conclusion:
TMS can be used to reliably identify corticomotor alterations after therapeutic interventions, as well as monitor disease progression.
Daniel H. Huffman, Brian G. Pietrosimone, Terry L. Grindstaff, Joseph M. Hart, Susan A. Saliba, and Christopher D. Ingersoll
Context:
Motoneuron-pool facilitation after cryotherapy may be mediated by stimulation of thermoreceptors surrounding a joint. It is unknown whether menthol counterirritants, which also stimulate thermoreceptors, have the same effect on motoneuron-pool excitability (MNPE).
Objective:
To compare quadriceps MNPE after a menthol-counterirritant application to the anterior knee, a sham counterirritant application, and a control treatment in healthy subjects.
Design:
A blinded, randomized controlled laboratory study.
Setting:
Laboratory.
Participants:
Thirty healthy subjects (16 m, 14 f; 24.1 ± 3.9 y, 170.6 ± 11.4 cm, 72.1 ± 15.6 kg) with no history of lower extremity surgery volunteered for this study.
Intervention:
Two milliliters of menthol or sham counterirritant was applied to the anterior knee; control subjects received no intervention.
Main Outcome Measures:
The average vastus medialis normalized Hoffmann reflex (Hmax:Mmax ratio) was used to measure MNPE. Measurements were recorded at 5, 15, 25, and 35 minutes postintervention and compared with baseline measures.
Results:
Hmax:Mmax ratios for all groups significantly decreased over time (F 4,108 = 10.52, P < .001; menthol: baseline = .32 ± .20, 5 min = .29 ± .18, 15 min = .27 ± .18, 25 min = .28 ± .19, 35 min = .27 ± .18; sham: baseline = .46 ± .26, 5 min = .36 ± .20, 15 min = .35 ± .19, 25 min = .35 ± .20, 35 min = .34 ± .18; control: baseline = .48 ± .32, 5 min = .37 ± .27, 15 min = .37 ± .27, 25 min = .37 ± .29, 35 min = .35 ± .28). No significant Group × Time interaction or group differences in Hmax:Mmax were found.
Conclusions:
Menthol did not affect quadriceps MNPE in healthy subjects.
Adam S. Lepley, Allison M. Strouse, Hayley M. Ericksen, Kate R. Pfile, Phillip A. Gribble, and Brian G. Pietrosimone
Context:
Components of gluteal neuromuscular function, such as strength and corticospinal excitability, could potentially influence alterations in lower extremity biomechanics during jump landing.
Objective:
To determine the relationship between gluteal muscle strength, gluteal corticospinal excitability, and jump-landing biomechanics in healthy women.
Setting:
University laboratory.
Design:
Descriptive laboratory study.
Participants:
37 healthy women (21.08 ± 2.15 y, 164.8 ± 5.9 cm, 65.4 ± 12.0 kg).
Interventions:
Bilateral gluteal strength was assessed through maximal voluntary isometric contractions (MVIC) using an isokinetic dynamometer. Strength was tested in the open chain in prone and side-lying positions for the gluteus maximus and gluteus medius muscles, respectively. Transcranial magnetic stimulation was used to elicit measures of corticospinal excitability. Participants then performed 3 trials of jump landing from a 30-cm box to a distance of 50% of their height, with an immediate rebound to a maximal vertical jump. Each jump-landing trial was video recorded (2-D) and later scored for errors.
Main Outcome Measures:
MVICs normalized to body mass were used to assess strength in the gluteal muscles of the dominant and nondominant limbs. Corticospinal excitability was assessed by means of active motor threshold (AMT) and motor-evoked potentials (MEP) elicited at 120% of AMT. The Landing Error Scoring System (LESS) was used to evaluate jump-landing biomechanics.
Results:
A moderate, positive correlation was found between dominant gluteus maximus MEP and LESS scores (r = .562, P = .029). No other significant correlations were observed for MVIC, AMT, or MEP for the gluteus maximus and gluteus medius, regardless of limb.
Conclusions:
The findings suggest a moderate relationship between dominant gluteus maximus corticospinal excitability and a clinical measure of jump-landing biomechanics. Further research is required to substantiate the findings and expand our understanding of the central nervous system’s role in athletic movement.
