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Mark A. Sutherlin, L. Colby Mangum, Jay Hertel, Susan A. Saliba and Joseph M. Hart

Ultrasound imaging has been used to assess muscle function of deeper muscles and to compare individuals with and without low back pain. These measures may be influenced by numerous factors requiring normalization for these comparisons. The purpose of this study was to assess anthropometric normalization variables with muscle thickness of the transversus abdominis and lumbar multifidus across multiple ultrasound testing positions. Numerous anthropometric variables were correlated with muscle thickness. Mass, body mass index, and height times mass show the best promise for normalization, but were not consistent for the transversus abdominis and lumbar multifidus muscles. Normalization strategies should be considered when comparing between groups.

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Alyssa Muething, Shellie Acocello, Kimberly A. Pritchard, Stephen F. Brockmeier, Susan A. Saliba and Joseph M. Hart

Context:

Understanding how muscles activate in a population with a previous glenohumeral-joint (GH) injury may help clinicians understand how to build a conservative treatment plan to strengthen or activate the specific muscles in an attempt to reduce recurrent shoulder injury and development of GH laxity.

Objective:

To investigate muscle-activation differences between the previously injured limb of individuals with a history of GH-joint injury and healthy matched controls during functional isometric contractions.

Design:

Case control.

Setting:

University research laboratory.

Participants:

17 individuals (8 women, 9 men; age 22.3 ± 2.6 y, height 172.4 ± 8.8 cm, mass 75.4 ± 16.5 kg) with previous unilateral shoulder pain and 17 (8 women, 9 men; age 22.9 ± 3.9 y, height 170.9 ± 11.3 cm, mass 73.6 ± 22.9 kg) with no history of shoulder pain or injury.

Intervention(s):

Diagnostic ultrasound measurements of the supraspinatus were completed in both resting and contracted states to assess changes in muscle thickness. Manual muscle tests (anterior deltoid, upper trapezius, infraspinatus, lower trapezius, serratus anterior) and functional isometric contractions (forward flexion, scaption, abduction) were measured using electromyography.

Main Outcome Measures:

Peak, normalized activation of each muscle and supraspinatus thickness activation ratio were compared between groups and bilaterally within groups using separate ANOVAs.

Results:

The anterior deltoid was significantly less activated during all functional isometric tasks in previously injured subjects than in healthy subjects (P = .024). In previously injured subjects, the involved limb-lower trapezius was significantly less activated during scaption and abduction tasks than the contralateral side (P = .022 and P = .031, respectively).

Conclusions:

There were decreases in muscle activation in the anterior deltoid between previously injured and healthy people, as well as in the lower trapezius, in previously injured subjects. Understanding the source of muscle-activation deficits can help clinicians focus rehabilitation exercises on specific muscles.

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Mark A. Sutherlin, L. Colby Mangum, Shawn Russell, Susan Saliba, Jay Hertel and Joe M. Hart

Context: Reduced spinal stabilization, delayed onset of muscle activation, and increased knee joint stiffness have been reported in individuals with a history of low back pain (LBP). Biomechanical adaptations resulting from LBP may increase the risk for future injury due to suboptimal loading of the lower-extremity or lumbar spine. Assessing landing mechanics in these individuals could help identify which structures might be susceptible to future injury. Objective: To compare vertical and joint stiffness of the lower-extremity and lumbar spine between individuals with and without a previous history of LBP. Design: Cross-sectional study. Setting: Research laboratory. Participants: There were 45 participants (24 without a previous history of LBP—age 23 [8] y, height 169.0 [8.5] cm, mass 69.8 [13.8] kg; 21 with a previous history of LBP—age 25[9] y, height 170.0 [8.0] cm, mass 70.2 [11.8] kg). Interventions: Single-limb landing trials on the dominant and nondominant limb from a 30-cm box. Main Outcome Measures: Vertical stiffness and joint stiffness of the ankle, knee, hip, and lumbar spine. Results: Individuals with a previous history of LBP had lower vertical stiffness (P = .04), but not joint stiffness measures compared with those without a previous history of LBP (P > .05). Overall females had lower vertical (P = .01), ankle (P = .02), and hip stiffness (P = .04) compared with males among all participants. Males with a previous history of LBP had lower vertical stiffness compared with males without a previous history LBP (P = .01). Among all individuals without a previous history of LBP, females had lower vertical (P < .01) and ankle stiffness measures (P = .04) compared with males. Conclusions: Landing stiffness may differ among males and females and a previous history of LBP. Comparisons between individuals with and without previous LBP should be considered when assessing landing strategies, and future research should focus on how LBP impacts landing mechanics.

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Rebecca J. Guthrie, Terry L. Grindstaff, Theodore Croy, Christopher D. Ingersoll and Susan A. Saliba

Context:

Individuals with low back pain (LBP) are thought to benefit from interventions that improve motor control of the lumbopelvic region. It is unknown if therapeutic exercise can acutely facilitate activation of lateral abdominal musculature.

Objective:

To investigate the ability of 2 types of bridging-exercise progressions to facilitate lateral abdominal muscles during an abdominal drawing-in maneuver (ADIM) in individuals with LBP.

Design:

Randomized control trial.

Setting:

University research laboratory.

Participants:

51 adults (mean ± SD age 23.1 ± 6.0 y, height 173.6 ± 10.5 cm, mass 74.7 ± 14.5 kg, and 64.7% female) with LBP. All participants met 3 of 4 criteria for stabilization-classification LBP or at least 6 best-fit criteria for stabilization classification.

Interventions:

Participants were randomly assigned to either traditional-bridge progression or suspension-exercise-bridge progression, each with 4 levels of progressive difficulty. They performed 5 repetitions at each level and were progressed based on specific criteria.

Main Outcome Measures:

Muscle thickness of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) was measured during an ADIM using ultrasound imaging preintervention and postintervention. A contraction ratio (contracted thickness:resting thickness) of the EO, IO, and TrA was used to quantify changes in muscle thickness.

Results:

There was not a significant increase in EO (F 1,47 = 0.44, P = .51) or IO (F 1,47 = .30, P = .59) contraction ratios after the exercise progression. There was a significant (F 1,47 = 4.05, P = .05) group-by-time interaction wherein the traditional-bridge progression (pre = 1.55 ± 0.22; post = 1.65 ± 0.21) resulted in greater (P = .03) TrA contraction ratio after exercise than the suspension-exercise-bridge progression (pre = 1.61 ± 0.31; post = 1.58 ± 0.28).

Conclusion:

A single exercise progression did not acutely improve muscle thickness of the EO and IO. The magnitude of change in TrA muscle thickness after the traditional-bridging progression was less than the minimal detectable change, thus not clinically significant.

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Grant E. Norte, Jay N. Hertel, Susan A. Saliba, David R. Diduch and Joseph M. Hart

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.

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Alexandra F. DeJong, L. Colby Mangum, Jacob E. Resch and Susan A. Saliba

Context: Medial knee displacement (MKD) is a common risk factor for lower-extremity injury and is related to altered gluteal muscle activity. Ultrasound imaging (USI) is a reliable means to explore mechanical muscle activity; however, no information exists regarding USI of the gluteals during gait in an MKD population. Objective: To determine differences in USI gluteal muscle activity during gait in individuals with and without MKD. Design: Descriptive laboratory study. Setting: University research laboratory. Participants: Out of 28 participants, 14 exhibiting MKD unilaterally during a single-leg squat (19.36 [1.51] y, 169.73 [7.50] cm, and 62.01 [10.57] kg; 10 females) and 14 matched non-MKD subjects (20.29 [1.73] y, 167.24 [9.07] cm, and 67.53 [16.03] kg). Interventions: Bilateral B-mode USI of the gluteus maximus (Gmax) and gluteus medius (Gmed) muscles during quiet stance, heel strike, and a 10-second treadmill walking clip. Main Outcome Measures: Gluteal thickness measures normalized to quiet stance yielded activity ratios, and percentage of muscle thickness change was assessed between heel strike and quiet stance. Differences between groups were assessed with Cohen’s d effect sizes with 95% confidence intervals. Activity ratios with 90% confidence intervals plotted on 10% intervals from 0% to 100% of gait were used to compare groups and limbs. A subsample of images was measured to determine intertester reliability. Results: USI revealed decreased Gmax and Gmed percent change at heel strike (%change = −9.57% [7.15%] and −8.76% [4.26%], respectively). The MKD limb compared with the contralateral limb exhibited decreased Gmed activity ratio at 30% of gait (MKD = 0.89 [0.056]; non-MKD = 1.01 [.052]). Intertester reliability was excellent for gluteus maximus (intraclass correlation coefficient = .987 [.014]) and Gmed (intraclass correlation coefficient = .989 [.013]) measurements. Conclusions: USI highlighted gluteal activity differences of MKD limbs during gait, which may contribute to inadequate hip stabilization during this daily repetitive task. These findings potentiate the use of USI as an intervention- or screening-based visual tool.

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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.

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Shandi L. Partner, Mark Alan Sutherlin, Shellie Acocello, Susan A. Saliba, Eric M. Magrum and Joe M. Hart

Context:

Individuals with low back pain (LBP) have reduced function of the transversus abdominis (TrA) and lumbar multifidus (LM) muscles. Biofeedback during exercise may increase the ability to contract the TrA and LM muscles compared with exercise alone.

Objective:

To compare TrA preferential activation ratio (PAR) and the percent change in LM-muscle thickness in patients with LBP history before and after exercise with or without biofeedback.

Design:

Controlled laboratory study.

Setting:

University research laboratory.

Patients:

20 LBP individuals, 10 exercise alone and 10 exercise with biofeedback.

Interventions:

Patients were allotted to tabletop exercises in isolation or tabletop exercises with visual, auditory, and tactile biofeedback.

Main Outcome Measures:

TrA PAR and percent change in LM-muscle thickness.

Results:

There were no differences between groups at baseline (all P > .05). Nonparametric statistics showed decreased resting muscle thickness for total lateral abdominal-wall muscles (P = .007) but not TrA (P = .410) or LM (P = .173). Percent TrA thickness increased from table to standing positions before (P = .006) and after exercise (P = .009). TrA PAR increased after exercise (pre 0.01 ± 0.02, post 0.03 ± 0.04, P = .033) for all patients and for exercise with biofeedback (pre 0.02 ± 0.01, post 0.03 ± 0.01, P = .037) but not for exercise alone (pre 0.01 ± 0.02, post 0.02 ± 0.05, P = .241). No group differences were observed for TrA PAR before (exercise 0.01 ± 0.02, exercise with biofeedback 0.02 ± 0.01, P = .290) or after exercise (exercise 0.02 ± 0.05, exercise with biofeedback 0.03 ± 0.01, P = .174). There were no group differences in LM percent change before exercise (P = .999) or after exercise (P = .597). In addition, no changes were observed in LM percent change as a result of exercise among all participants (P = .391) or for each group (exercise P = .508, exercise with biofeedback P = .575).

Conclusion:

TrA PAR increased after a single session of exercises, whereas no thickness changes occurred in LM.

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Hailey N. Love, Kimberly A. Pritchard, Joseph M. Hart and Susan A. Saliba

Context:

Alterations in skin sensations may be responsible for pain reduction provided by cryotherapy, but the exact physiological mechanism is unknown.

Objective:

To investigate perceptions of skin sensations associated with different modes of cryotherapy administration and skin temperature at the point of perceived numbness.

Design:

Repeated measures.

Participants:

30 healthy subjects (12 Male, 18 Female, Age = 21.1±1.9 years).

Interventions:

Crushed ice bag, ice massage, and cold water immersion.

Main Outcome Measures:

Perceptions of sensations during each mode of cryotherapy administration were derived from a Modified McGill Pain Questionnaire. Skin temperature was recorded when numbness was reported for each treatment.

Results:

Participants experienced sensations that included cold, tight, tingling, stinging, and numb. Ice massage sensations transitioned rapidly from cold to numb, whereas cold water immersion and ice bag treatments produced altered sensations for longer duration. Ice massage decreased skin temperature significantly more than the other two modes of cryotherapy administration.

Conclusions:

Ice massage may be the best mode of cryotherapy administration for achievement of anaesthesia as rapidly as possible, whereas cold water immersion and ice bag application may be better for attainment of pain reduction associated with noxious stimulation of skin receptors.

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Jenna K. Cataldi, Kimberly A. Pritchard, Joseph M. Hart and Susan A. Saliba

Context:

Recommended treatment duration for cryotherapy varies, but the primary therapeutic benefit may be related to the amount of time required for changes in cutaneous sensation.

Objective:

To determine the amount of time required to induce numbness for three different modes of cryotherapy administration, and the amount of time that numbness persists after treatment.

Design:

Repeated measures.

Participants:

30 healthy adults (12 males, 18 females, age = 21.1 ± 1.9 years).

Interventions:

Crushed ice bag, ice massage, and cold water immersion.

Main Outcome Measures:

Time required to induce numbness and the amount of time numbness remained after removal of each mode of cryotherapy.

Results:

Ice massage and cold water immersion produced numbness significantly faster than the crushed ice. There were no significant differences in terms of numbness duration.

Conclusions:

Changes in cutaneous sensation can be achieved in a relatively short amount of time (6–12 minutes) with ice massage and cold water immersion. The duration of the treatment effect did not differ among the three modes of cryotherapy administration.