Quadriceps arthrogenic muscle inhibition: neural mechanisms and treatment perspectives

Local vibration training improves the recovery of quadriceps strength in early rehabilitation after anterior cruciate ligament reconstruction: A feasibility randomised controlled trial

BACKGROUND

After anterior cruciate ligament reconstruction (ACLR), quadriceps strength must be maximised as early as possible.

OBJECTIVES

We tested whether local vibration training (LVT) during the early post-ACLR period (i.e., ∼10 weeks) could improve strength recovery.

METHODS

This was a multicentric, open, parallel-group, randomised controlled trial. Thirty individuals attending ACLR were randomised by use of a dedicated Web application to 2 groups: vibration (standardised rehabilitation plus LVT, n=16) or control (standardised rehabilitation alone, n=14). Experimenters, physiotherapists and participants were not blinded. Both groups received 24 sessions of standardised rehabilitation over ∼10 weeks. In addition, the vibration group received 1 hour of vibration applied to the relaxed quadriceps of the injured leg at the end of each rehabilitation session. The primary outcome - maximal isometric strength of both injured and non-injured legs (i.e., allowing for limb asymmetry measurement) - was evaluated before ACLR (PRE) and after the 10-week rehabilitation (POST).

RESULTS

Seven participants were lost to follow-up, so data for 23 participants were used in the complete-case analysis. For the injured leg, the mean (SD) decrease in maximal strength from PRE to POST was significantly lower for the vibration than control group (n=11, -16% [10] vs. n=12, -30% [11]; P=0.0045, Cohen's d effect size=1.33). Mean PRE-POST change in limb symmetry was lower for the vibration than control group (-19% [11] vs. -29% [13]) but not significantly (P=0.051, Cohen's d effect size=0.85).

CONCLUSION

LVT improved strength recovery after ACLR. This feasibility study suggests that LVT applied to relaxed muscles is a promising modality of vibration therapy that could be implemented early in ACLR.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02929004.

One Session Effects of Knee Motion Visualization Using Immersive Virtual Reality in Patients with Hemophilic Arthropathy

(1) Background: Hemophilic knee arthropathy is characterized by a loss of muscle mass and decreased strength of the quadriceps muscle. The visualization of movement aims to favor the recruitment of the motor system in the same premotor and parietal areas, as would happen with the active execution of the observed action. The aim was to evaluate changes in quadriceps activation in patients with hemophilic knee arthropathy following immersive VR visualization of knee extension movements. (2) Methods: We recruited 13 patients with severe hemophilia A and knee arthropathy. Patients underwent a 15 min session of immersive VR visualization of knee extension movements. The quadriceps muscle activation was evaluated by surface electromyography. (3) Results: After the intervention, there were no changes in the muscle activation of vastus medialis, vastus lateralis, or rectus femoris muscles. There was a large effect size of changes in rectus femoris muscle activation. Age and knee joint damage did not correlate with changes in quadriceps activation. Dominance, inhibitor development, and type of treatment were not related with post-intervention muscle activation. (4) Conclusions: A session of immersive VR visualization of knee extension movement does not modify quadriceps muscle activation. A specific protocol for patients with hemophilic knee arthropathy may be effective in improving the activation of the rectus femoris muscle.

Deficit in knee extension strength following anterior cruciate ligament reconstruction is explained by a reduced neural drive to the vasti muscles

The persistence of quadriceps weakness represents a major concern following anterior cruciate ligament reconstruction (ACLR). The underlying adaptations occurring in the activity of spinal motoneurons are still unexplored. This study examined the discharge patterns of large populations of motor units (MUs) in the vastus lateralis (VL) and vastus medialis muscles following ACLR. Nine ACLR individuals and 10 controls performed unilateral trapezoidal contractions of the knee extensor muscles at 35%, 50% and 70% of the maximal voluntary isometric force (MVIF). High-density surface electromyography (HDsEMG) was used to record the myoelectrical activity of the vasti muscles in both limbs. HDsEMG signals were decomposed with a convolutive blind source separation method and MU properties were extracted and compared between sides and groups. The ACLR group showed a lower MVIF on the reconstructed side compared to the contralateral side (28.1%; P < 0.001). This force deficit was accompanied by reduced MU discharge rates (∼21%; P < 0.05), lower absolute MU recruitment and derecruitment thresholds (∼22% and ∼22.5%, respectively; P < 0.05) and lower input-output gain of motoneurons (27.3%; P = 0.009). Deficits in MU discharge rates of the VL and in absolute recruitment and derecruitment thresholds of both vasti MUs were associated with deficits in MVIF (P < 0.05). A strong between-side correlation was found for MU discharge rates of the VL of ACLR individuals (P < 0.01). There were no significant between-group differences (P > 0.05). These results indicate that mid- to long-term strength deficits following ACLR may be attributable to a reduced neural drive to vasti muscles, with potential changes in excitatory and inhibitory synaptic inputs. KEY POINTS: Impaired expression and control of knee extension forces is common after anterior cruciate ligament reconstruction and is related to high risk of a second injury. To provide novel insights into the neural basis of this impairment, the discharge patterns of motor units in the vastus lateralis and vastus medialis were investigated during voluntary force contractions. There was lower knee extensor strength on the reconstructed side with respect to the contralateral side, which was explained by deficits in motor unit discharge rate and an altered motoneuronal input-output gain. Insufficient excitatory inputs to motoneurons and increased inhibitory afferent signals potentially contributed to these alterations. These results further our understanding of the neural underpinnings of quadriceps weakness following anterior cruciate ligament reconstruction and can help to develop effective rehabilitation protocols to regain muscle strength and reduce the risk of a second injury.

Time to Save Time: Beneficial Effects of Blood Flow Restriction Training and the Need to Quantify the Time Potentially Saved by Its Application During Musculoskeletal Rehabilitation

The main goal of musculoskeletal rehabilitation is to achieve the pre-injury and/or pre-surgery physical function level with a low risk of re-injury. Blood flow restriction (BFR) training is a promising alternative to conventional therapy approaches during musculoskeletal rehabilitation because various studies support its beneficial effects on muscle mass, strength, aerobic capacity, and pain perception. In this perspective article, we used an evidence-based progressive model of a rehabilitative program that integrated BFR in 4 rehabilitation phases: (1) passive BFR, (2) BFR combined with aerobic training, (3) BFR combined with low-load resistance training, and (4) BFR combined with low-load resistance training and traditional high-load resistance training. Considering the current research, we propose that a BFR-assisted rehabilitation has the potential to shorten the time course of therapy to reach the stage where the patient is able to tolerate resistance training with high loads. The information and arguments presented are intended to stimulate future research, which compares the time to achieve rehabilitative milestones and their physiological bases in each stage of the musculoskeletal rehabilitation process. This requires the quantification of BFR training-induced adaptations (eg, muscle mass, strength, capillary-to-muscle-area ratio, hypoalgesia, molecular changes) and the associated changes in performance with a high measurement frequency (≤1 week) to test our hypothesis. This information will help to quantify the time saved by BFR-assisted musculoskeletal rehabilitation. This is of particular importance for patients, because the potentially accelerated recovery of physical functioning would allow them to return to their work and/or social life earlier. Furthermore, other stakeholders in the health care system (eg, physicians, nurses, physical therapists, insurance companies) might benefit from that with regard to work and financial burden.

Should We Trust Perceived Effort for Loading Control and Resistance Exercise Prescription After ACL Reconstruction?

CONTEXT

The rating of perceived effort (RPE) is a common method used in clinical practice for monitoring, loading control, and resistance training prescription during rehabilitation after rupture and anterior cruciate ligament reconstruction (ACLR). It is suggested that the RPE results from the integration of the afferent feedback and corollary discharge in the motor and somatosensory cortex, and from the activation of brain areas related to emotions, affect, memory, and pain (eg, posterior cingulate cortex, precuneus, and prefrontal cortex). Recent studies have shown that rupture and ACLR induce neural adaptations in the brain commonly associated with the RPE. Therefore, we hypothesize that RPE could be affected because of neural adaptations induced by rupture and ACLR.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

RPE could be directly altered by changes in the activation of motor cortex, posterior cingulate cortex, and prefrontal cortex. These neural adaptations may be induced by indirect mechanisms, such as the afferent feedback deficit, pain, and fear of movement (kinesiophobia) that patients may feel after rupture and ACLR.

CONCLUSION

Using only RPE for monitoring, loading control, and resistance training prescription in patients who had undergone ACLR could lead to under- or overdosing resistance exercise, and therefore, impair the rehabilitation process.

STRENGTH-OF-RECOMMENDATION TAXONOMY

3C.

Mechanisms of Arthrogenic Muscle Inhibition

CONTEXT

Arthrogenic muscle inhibition (AMI) continues to be a limiting factor in joint rehabilitation as the inability to volitionally activate muscle significantly dampens recovery. New evidence acquired at higher brain centers and in clinical populations continues to reshape our perspective of what AMI is and how to treat it. This review aims to stimulate discussion about the far-reaching effects of AMI by exploring the interconnected pathways by which it evolves.

OBJECTIVES

To discuss how reflexive inhibition can lead to adaptations in brain activity, to illustrate how changes in descending motor pathways limit our ability to contract muscle following injury, and to summarize the emerging literature on the wide-reaching effects of AMI on other interconnected systems.

DATA SOURCES

The databases PubMed, SPORTDiscus, and Web of Science were searched for articles pertaining to AMI. Reference lists from appropriate articles were cross-referenced.

CONCLUSION

AMI is a sequential and cumulative neurological process that leads to complex clinical impairments. Originating with altered afferent information arising from an injured joint, patients experience changes in afferent information, reflexive muscle inhibition, deficiencies in somatosensation, neuroplastic compensations in higher brain centers, and ultimately decreased motor output to the muscle surrounding the joint. Other aspects of clinical function, like muscle structure and psychological responses to injury, are also impaired and influenced by AMI. Removing, or reducing, AMI should continue to be a focus of rehabilitation programs to assist in the optimization of health after joint injury.

Differences in the mass and quality of the quadriceps with age and sex and their relationships with knee extension strength

BACKGROUND

Although muscle quality evaluations are currently considered important for diagnosing sarcopenia, data from the general population are lacking. This study used mid-thigh computed tomography measurements to evaluate age-related and sex-related differences in quadriceps femoris muscle quality and mass and their relationships with knee extension strength (KES).

METHODS

Cross-sectional data from 520 Japanese individuals (273 men and 247 women, mean age: 63.1 ± 10.6 years) were analysed. Mass and quality were assessed using quadriceps cross-sectional areas (CSAs) and computed tomography values (CTVs), respectively. The four constituent muscles, intermuscular adipose tissue, and entire quadriceps area (total quadriceps muscles + intermuscular adipose tissue) were assessed, and the data were stratified by five age groups and sex. To evaluate age-related decline, linear and quadratic equations were tested for fit according to the constituent muscles and sex. KES could be measured in 472 of the 520 participants (254 men and 218 women, mean age: 62.3 ± 10.3). Multiple linear regression analyses with age-adjusted models were then used for evaluating the relationships between KES and quadriceps measurements.

RESULTS

All muscle CSAs and CTVs showed downward trends with age (men: P < 0.001 for all; women: vastus medialis CTV, P = 0.004; others, P < 0.001); the intermuscular adipose tissue CSA did not show any trend (men: P = 0.938; women: P = 0.139), although its percentage of the entire quadriceps area showed an upward trend in both sexes (P < 0.001). Men exhibited a quadratic decline in the CSAs for the entire quadriceps area (P = 0.016), total quadriceps muscles (P = 0.021), the vastus medialis (P = 0.010) and vastus lateralis (P = 0.038), and all CTVs (rectus femoris, P = 0.044; others, P < 0.001). Women exhibited a quadratic equation in the CTV for rectus femoris (P = 0.031), but a linear decline in the other variables (P < 0.001 for all). Both the total quadriceps muscles CSA and CTV were significantly associated with KES in both sexes (P < 0.001). For each muscle, the CSAs of the vastus medialis (P < 0.001) and vastus intermedius (P = 0.001) were significantly associated with KES in men, whereas the vastus medialis CSA (P < 0.001), vastus lateralis CSA (P = 0.006), rectus femoris CSA (P = 0.020), and vastus intermedius CTV (P = 0.025) were significantly associated with KES in women CONCLUSIONS: Age-related quadriceps femoris changes in mass and quality differed by sex and the constituent muscles. The constituent muscles contributing to KES differed between men and women. Quadriceps CSA and CTV measurements are useful for objectively assessing age-related and sex-related muscle deterioration and KES.

Muscle Activity and Activation in Previously Strain-Injured Lower Limbs: A Systematic Review

BACKGROUND

Lower limb muscle strain injury is highly prevalent in running-based sports and is considered a risk factor for recurrent injury. It is possible that differences in muscle activity and activation in previously strain-injured limbs may contribute to the elevated risk of reinjury.

OBJECTIVES

To systematically review available literature investigating whether muscle activity and/or activation is different in previously strain-injured muscles compared to contralateral uninjured muscles or uninjured controls.

METHODS

A systematic review of literature in SPORTDiscus, MEDLINE Complete, CINAHL and Web of Science was conducted. Full-text English articles which compared indicators of neuromuscular function between injured and uninjured contralateral limbs or control groups in those with a history of muscle strain injury were included.

RESULTS

Twelve studies were included in the review after eligibility criteria were applied. A best evidence synthesis revealed moderate to limited evidence suggesting differences in surface electromyography (sEMG) amplitude, integrated sEMG amplitude, inter-muscle sEMG ratios and voluntary activation in injured limbs, most often during eccentric contractions. Studies utilising sprinting assessments demonstrated conflicting evidence when comparing late swing phase biceps femoris sEMG amplitude between limbs with a history of hamstring strain injury and uninjured contralateral limbs.

CONCLUSIONS

Differences in muscle activity and activation were observed between injured and uninjured limbs across a variety of strength assessments. The evidence supporting these differences was most often moderate or limited and was generally observed during eccentric contractions. Mostly conflicting or limited evidence was found to suggest that participants with previous hamstring strain injury demonstrate no differences in muscle activity during running tasks when compared with their uninjured counterparts or contralateral limbs.

TRIAL REGISTRY

PROSPERO (ID, CRD42019135681).

Combined neuromuscular electrical stimulation with motor control exercise can improve lumbar multifidus activation in individuals with recurrent low back pain

Motor control exercise (MCE) is commonly prescribed for patients with low back pain. Although MCE can improve clinical outcomes, lumbar multifidus muscle (LM) activation remains unchanged. Neuromuscular electrical stimulation (NMES) can be used to re-activate motor units prior to MCE which should result in increased LM activation. Therefore, this study aimed to explore the immediate effects of NMES combined with MCE on LM activation and motor performance. Twenty-five participants without low back pain (NoLBP) and 35 participants with movement control impairment (MCI) were recruited. Participants with MCI were further randomized to combined NMES with MCE (COMB) or sham-NMES with MCE (MCE) group. Ultrasound imaging was used to measure LM thickness at rest, maximum voluntary isometric contraction (MVIC), and NMES with MVIC. These data were used to calculate LM activation. Quadruped rocking backward was used to represent motor performance. LM activation and motor performance were measured at baseline and after one-session of intervention. Results showed that both COMB and MCE groups had significantly lower (P < 0.05) LM activation compared with NoLBP group at baseline. Additionally, both COMB and MCE groups demonstrated significant improvement (P < 0.05) in motor performance while COMB group demonstrated significantly greater improvement (P < 0.05) in LM activation compared with MCE group. Individuals with MCI still have persisting LM activation deficit. Our key findings suggest that combined NMES and MCE may have better ability to improve LM activation in individuals with MCI. These findings would support the utility of NMES to induce a priming effect before MCE.

Patients with chronic unilateral anterior knee pain experience bilateral deficits in quadriceps function and lower quarter flexibility: a cross-sectional study

Background: Little is known about how chronic unilateral anterior knee pain (AKP) affects bilateral quadriceps function and lower quarter flexibility. Objective: To determine if patients with chronic unilateral AKP present bilateral deficits in quadriceps function and lower quarter flexibility. Methods: Twenty-two patients with chronic unilateral AKP (pain duration: 48.6 months) and 22 matched healthy controls were evaluated. Pain perception and functional outcomes were obtained. Knee joint and thigh circumferences, quadriceps subcutaneous tissue thickness and function (i.e. maximal and explosive strength, activation, and endurance), and lower quarter flexibility (i.e. hamstrings and iliopsoas/rectus femoris muscle) in both legs were compared across conditions. Results: Knee joint and thigh circumferences, and quadriceps subcutaneous tissue thickness were not different between conditions (P ≥ .39). Compared with matched healthy controls, patients with chronic unilateral AKP showed: 1) greater pain perception (0.0 versus 4.4 cm, P < .0001); 2) a lower score for functional outcomes (79.6 versus 53.9, P < .0001); 3) less bilateral quadriceps maximal (3.5 versus 2.8 Nm/kg, P < .0001) and explosive (10.8 versus 8.7 Nm/kg/s, P = .01) strength, activation (0.95 versus 0.83, P < .0001), and endurance (1.66 versus 1.52 Nm/kg, P = .02); and 4) less bilateral hamstrings (86.8 versus 72.6°, P = .002) and iliopsoas/rectus femoris (11.6 versus 7.8°, P < .05) flexibility. Conclusion: Patients with chronic unilateral AKP (without knee joint effusion or quadriceps muscle atrophy) appear to have bilateral deficits in quadriceps function and lower quarter flexibility, which should be addressed with pain reduction.

Durability of the Therapeutic Effect of Restorative Neurostimulation for Refractory Chronic Low Back Pain

Objectives

The purpose of the ongoing follow‐up of ReActiv8‐A clinical trial is to document the longitudinal benefits of episodic stimulation of the dorsal ramus medial branch and consequent contraction of the lumbar multifidus in patients with refractory mechanical chronic low back pain (CLBP). We report the four‐year outcomes of this trial.

Materials and Methods

ReActiv8‐A is a prospective, single‐arm trial performed at nine sites in the United Kingdom, Belgium, and Australia. Eligible patients had disabling CLBP (low back pain Numeric Rating Scale [NRS] ≥6; Oswestry Disability Index [ODI] ≥25), no indications for spine surgery or spinal cord stimulation, and failed conventional management including at least physical therapy and medications for low back pain. Fourteen days postimplantation, stimulation parameters were programmed to elicit strong, smooth contractions of the multifidus, and participants were given instructions to activate the device for 30‐min stimulation‐sessions twice daily. Annual follow‐up through four years included collection of NRS, ODI, and European Quality of Life Score on Five Dimensions (EQ‐5D). Background on mechanisms, trial design, and one‐year outcomes were previously described.

Results

At baseline (N = 53) (mean ± SD) age was 44 ± 10 years; duration of back pain was 14 ± 11 years, NRS was 6.8 ± 0.8, ODI 44.9 ± 10.1, and EQ‐5D 0.434 ± 0.185. Mean improvements from baseline were statistically significant (p < 0.001) and clinically meaningful for all follow‐ups. Patients completing year 4 follow‐up, reported mean (±standard error of the mean) NRS: 3.2 ± 0.4, ODI: 23.0 ± 3.2, and EQ‐5D: 0.721 ± 0.035. Moreover, 73% of participants had a clinically meaningful improvement of ≥2 points on NRS, 76% of ≥10 points on ODI, and 62.5% had a clinically meaningful improvement in both NRS and ODI and 97% were (very) satisfied with treatment.

Conclusions

In participants with disabling intractable CLBP who receive long‐term restorative neurostimulation, treatment satisfaction remains high and improvements in pain, disability, and quality‐of‐life are clinically meaningful and durable through four years.

Joint Corticosteroid Injection Associated With Higher Physical Therapy Compliance in Knee Osteoarthritis

Background Knee corticosteroid injection (KCSI) and physical therapy (PT) are two efficacious treatments for knee osteoarthritis (KOA). However, poor adherence to PT in resource-limited communities might limit its effectiveness. KCSI prior to PT might improve adherence in this population. Methodology This was a retrospective cohort analysis of patients referred to PT for KOA from January 01, 2018 to December 31, 2019 from an adult primary care resident clinic in Hartford, Connecticut, USA. Patients were divided into two groups, namely, those who had a KCSI around the time of the referral versus those who did not. PT adherence was evaluated in both groups. Results A total of 143 patients referred to PT were selected, and 11 patients were excluded. In total, 38/132 patients had a KCSI within a four-month window of the PT referral. Patients were mostly Hispanic (no injection 79.8% vs. injection 78.9%) females (80.9% vs. 71.1%), the average age was in the 60s, and over 90% were insured by either Medicaid or Medicare. In the injection group, 18/38 patients completed at least one PT visit (47.4%) versus 21/94 patients (22.3%) in the noninjection group. The odds ratio of undergoing PT was 1.38 (95% confidence interval [CI] = 1.14-1.69; p = 0.002), and the rate ratio of PT visits was 2.50 (95% CI = 1.82-3.42; p = 1.36 × 10-8), both adjusted for age, sex, and severity. Among those who attended at least one session, the mean number of PT visits was 5.4 in both injection and noninjection groups (median 5 versus 4).  Conclusions In a predominantly Hispanic patient population, those who underwent KCSI were more likely to undergo PT and, as a group, attend more sessions.

Altered Knee Laxity and Stiffness in Response to a Soccer Match Simulation in Players Returning to Sport Within 12 Months After Anterior Cruciate Ligament Reconstruction

BACKGROUND

The acute effects of exercise on anterior knee laxity (AKL) and anterior knee stiffness (AKS) have been documented in healthy participants, but only limited evidence has been provided for athletes cleared to return to sports after anterior cruciate ligament (ACL) reconstruction (ACLR).

PURPOSE/HYPOTHESIS

The purpose was to determine if 45 minutes of a soccer match simulation lead to acute changes in AKL and AKS in soccer players returning to sport within 12 months after ACLR. We hypothesized that the reconstructed knee of the ACLR group would exhibit an altered response to sport-specific exercise.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 13 soccer players cleared to return to sport after ACLR and 13 healthy control soccer players matched for age, physical activity level, limb dominance, and anthropometric characteristics were recruited. To assess the effects of a standardized soccer match simulation (Soccer Aerobic Field Test [SAFT45]) on AKL and AKS, an arthrometric evaluation was carried out bilaterally before and immediately after SAFT45. To conduct a comprehensive examination of the force-displacement curve, the absolute and side-to-side difference (SSD) values of both AKL and AKS were extracted at 67, 134, and 200 N.

RESULTS

The ACLR and control groups showed similar AKL and AKS at baseline (P > .05). In response to SAFT45, laxity increased bilaterally at all force levels by 14% to 17% only in the control group (P < .025). Similarly, AKS at 134 and 200 N decreased in response to SAFT45 only in the control group (10.5% and 20.5%, respectively; P < .025). After SAFT45, the ACLR group had 1.9 and 2.5 times higher SSDs of AKS at 67 and 134 N compared with the control group, respectively (P < .025), as well as a 1.9 times higher SSD of AKS at 134 N compared with baseline (P = .014).

CONCLUSION

Soccer players at the time of return to sport after ACLR showed an altered mechanical response to a sport-specific match simulation consisting of bilaterally unchanged AKL and AKS.

CLINICAL RELEVANCE

Soccer players showing altered AKL and AKS in response to exercise after ACLR may not be ready to sustain their preinjury levels of sport, thus potentially increasing the risk of second ACL injuries.

Low-Load Unilateral and Bilateral Resistance Training to Restore Lower Limb Function in the Early Rehabilitation After Total Knee Arthroplasty: A Randomized Active-Controlled Clinical Trial

Background: Continuous passive motion (CPM) is frequently used during rehabilitation following total knee arthroplasty (TKA). Low-load resistance training (LLRT) using continuous active motion (CAM) devices is a promising alternative. We investigated the effectiveness of CPM compared to LLRT using the affected leg (CAMuni) and both legs (CAMbi) in the early post-operative rehabilitation. Hypotheses: (I) LLRT (CAMuni and CAMbi) is superior to CPM, (II) additional training of the unaffected leg (CAMbi) is more effective than unilateral training (CAMuni).

Materials and Methods: Eighty-five TKA patients were randomly assigned to three groups, respectively: (i) unilateral CPM of the operated leg; (ii) unilateral CAM of the operated leg (CAMuni); (iii) bilateral alternating CAM (CAMbi). Patients were assessed 1 day before TKA (pre-test), 1 day before discharge (post-test), and 3 months post-operatively (follow-up). Primary outcome: active knee flexion range of motion (ROM_Flex). Secondary outcomes: active knee extension ROM (ROM_Ext), swelling, pain, C-reactive protein, quality of life (Qol), physical activity, timed-up-and-go performance, stair-climbing performance, quadriceps muscle strength. Analyses of covariances were performed (modified intention-to-treat and per-protocol).

Results: Hypothesis I: Primary outcome: CAMbi resulted in a higher ROM_Flex of 9.0° (95%CI −18.03–0.04°, d = 0.76) and 6.3° (95%CI −14.31–0.99°, d = 0.61) compared to CPM at post-test and follow-up, respectively. Secondary outcomes: At post-test, C-reactive protein was lower in both CAM groups compared with CPM. Knee pain was lower in CAMuni compared to CPM. Improved ROM_Ext, reduced swelling, better stair-climbing and timed-up-and-go performance were observed for CAMbi compared to CPM. At follow-up, both CAM groups reported higher Qol and CAMbi showed a better timed-up-and-go performance. Hypothesis II: Primary outcome: CAMbi resulted in a higher knee ROM_Flex of 6.5° (95%CI −2.16–15.21°, d = 0.56) compared to CAMuni at post-test. Secondary outcomes: At post-test, improved ROM_Ext, reduced swelling, and better timed-up-and-go performance were observed in CAMbi compared to CAMuni.

Conclusions: Additional LLRT of the unaffected leg (CAMbi) seems to be more effective for recovery of function than training of the affected leg only (CAMuni), which may be mediated by positive transfer effects from the unaffected to the affected limb (cross education) and/or preserved neuromuscular function of the trained, unaffected leg.

Trial Registration:ClinicalTrials.gov Identifier: NCT02062138.

Muscle strength and osteoarthritis progression after surgery or exercise for degenerative meniscal tears: Secondary analyses of a randomized trial

OBJECTIVE

To evaluate muscle strength changes following partial meniscectomy or exercise therapy for degenerative meniscal tears and the relationship between baseline muscle strength and osteoarthritis progression.

METHODS

Secondary analysis of a randomized trial (n=140 participants). Isokinetic quadriceps and hamstrings strength (peak torque [N·m/kg] and total work [J/kg]) were assessed at baseline, three-, 12-month, and five-year follow-up. Between-group differences were analyzed using intention-to-treat linear mixed models. The relationship between baseline muscle strength and osteoarthritis progression (Kellgren and Lawrence, ≥1 grade increase) were assessed using logistic regression models.

RESULTS

We found statistically significant between-group differences favoring exercise therapy at three months (quadriceps: -0.30 N·m/kg, 95% CI -0.40, -0.20; hamstrings: -0.10 N·m/kg, 95% CI -0.15, -0.04) and 12 months (quadriceps: -0.13 N·m/kg, 95% CI -0.23, -0.03; hamstrings: -0.08 N·m/kg, 95% CI -0.14, -0.03). At five years, between-group differences were -0.10 N·m/kg (95% CI -0.21 to 0.01) for quadriceps and -0.07 N·m/kg (95% CI -0.13 to -0.01) for hamstrings. Quadriceps muscle weakness at baseline was associated with knee osteoarthritis progression over five years: adjusted odds ratio of 1.40 for every 0.2 N·m/kg decrease (95% CI 1.15 to 1.71). The adjusted odds ratio for hamstrings was 1.14 (95% CI 0.97-1.35) for every 0.1 N·m/kg decrease.

CONCLUSION

Exercise therapy was effective in improving muscle strength at three and 12-month follow-up compared to partial meniscectomy, but the effect was attenuated at five years. Quadriceps muscle weakness at baseline was associated with higher odds of osteoarthritis progression over five years.

Slacklining: A narrative review on the origins, neuromechanical models and therapeutic use

Slacklining, the neuromechanical action of balance retention on a tightened band, is achieved through self-learned strategies combining dynamic stability with optimal energy expenditure. Published slacklining literature is recent and limited, including for neuromechanical control strategy models. This paper explores slacklining's definitions and origins to provide background that facilitates understanding its evolution and progressive incorporation into both prehabilitation and rehabilitation. Existing explanatory slacklining models are considered, their application to balance and stability, and knowledge-gaps highlighted. Current slacklining models predominantly derive from human quiet-standing and frontal plane movement on stable surfaces. These provide a multi-tiered context of the unique and complex neuro-motoric requirements for slacklining's multiple applications, but are not sufficiently comprehensive. This consequently leaves an incomplete understanding of how slacklining is achieved, in relation to multi-directional instability and complex multi-dimensional human movement and behavior. This paper highlights the knowledge-gaps and sets a foundation for the required explanatory control mechanisms that evolve and expand a more detailed model of multi-dimensional slacklining and human functional movement. Such a model facilitates a more complete understanding of existing performance and rehabilitation applications that opens the potential for future applications into broader areas of movement in diverse fields including prostheses, automation and machine-learning related to movement phenotypes.

No difference in long-term outcomes between men and women undergoing medial fixed-bearing cemented unicompartmental knee arthroplasty: A retrospective cohort study with minimum 10-year follow up

BACKGROUND

Some studies have suggested that women have poorer short-term outcomes after unicompartmental knee arthroplasty (UKA) due to a higher incidence of implant overhang. This study aimed to compare patient-reported outcome measures (PROMs) between men and women after UKA at a minimum follow-up of 10 years.

METHODS

Patients who underwent medial fixed-bearing UKA by two arthroplasty surgeons were identified from an institutional joint registry. Men and women were matched for age, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists class, range-of-motion and baseline PROMs using propensity scores. PROMs were compared at 2 and 10 years. Patients also completed a satisfaction questionnaire during these visits. Radiographic outliers were defined as > 2 mm of overhang.

RESULTS

A total of 128 patients were included. There was no difference in complications, length of stay or readmissions. Women had poorer Knee Society functional scores, Short-Form 36 physical and mental component scores (SF-36 MCS) at 2 years. No difference in PROMs was found at 10 years, except for poorer SF-36 MCS in women (P = 0.041). At 10 years, 96% of women and 92% of men were satisfied (P = 0.243). Fifteen-year survivorship free from any revision was 96% in each group. There were more medial-tibial outliers in women (9%) compared with men (5%) (P = 0.018). However, no association between outliers and outcomes or survivorship was found on multivariate analyses.

CONCLUSION

There was nodifference in clinical outcomes between men and women undergoing UKA at a minimum follow-up of 10 years. While women had a higher incidence of medial tibial overhang, this was not associated with long-term outcomes or survivorship.

Peripheral and Central Pathological Mechanisms of Chronic Low Back Pain: A Narrative Review

Chronic low back pain (CLBP), lasting >3 months, is the end result of multiple pathogenic factors. Unfortunately, little is known about CLBP pathogenesis, which limits its advancements in clinical therapy and disease management. This paper summarizes the known pathological axes of CLBP, involving both peripheral and central systems. In particular, this paper details injurious nerve stimulation, inflammation-induced peripheral pathway, and central sensitization. Lumbar components, such as intervertebral disc (IVD), facet joints, muscles, fascia, ligaments, and joint capsules, contain pain receptors called nociceptors. Degeneration of the aforementioned lumbar components activates inflammatory pathways, which can directly damage nerves, lower nociceptor threshold to fire action potentials (AP), and cause pain. Additionally, damaged lumbar IVDs and endplates can also lead to the pathologic invasion of nerve growth and innervation, followed by the compression of herniated IVDs on nerve roots, thereby causing traumatic neuropathic pain. The central mechanism of CLBP involves alteration of the sensory processing of the brain and malfunction of the descending pain modulatory system, which facilitates pain amplification in the center nervous system (CNS). Lastly, abnormalities in the brain biochemical metabolism, activation of glial cells, and subsequent inflammation also play important roles in CLBP development. Taken together, inflammation plays an important role in both peripheral and central sensitization of CLBP. Due to the heterogeneity of CLBP, its pathological mechanism remains complex and difficult to understand. Therefore, it is a worthy field for future research into the subcomponents of CLBP pathogenesis, in order to distinguish the specific form of the disease, identify its origins, and develop corresponding highly effective comprehensive therapy against CLBP.

Effects of Focal Knee Joint Cooling on Static and Dynamic Strength of the Quadriceps: Innovative Approach to Muscle Conditioning

Recent evidence suggests an innovative approach to muscle conditioning: focal knee joint cooling (FKJC) appears to improve quadriceps function, including static (isometric) strength. However, there is limited evidence on the effects of FKJC on dynamic (concentric and eccentric) strength. Thus, the purpose of the study was to examine dynamic quadriceps strength following FKJC as well as static strength. Twenty-one college-aged participants volunteered. They randomly underwent 20 min of FKJC and control condition at least 72 h apart. FKJC involves two ice bags, placed on the anterior and posterior surfaces of the knee, whereas the control condition received a plastic ice bag filled with candy corn. We assessed isometric and isokinetic (concentric and eccentric) quadriceps strength at two different velocities (60°/s and 180°/s). Participants performed three maximal voluntary contractions for each mode of muscle contraction, before and after each treatment (immediately, 20, and 40 min after). The outcome variable was maximum knee extension peak torque. FKJC did not change peak torque during any mode of muscle contraction (p > 0.05). The current findings suggest that 20 min of FKJC does not change static (isometric) or dynamic (isokinetic) strength of the quadriceps. FKJC was neither beneficial nor harmful to static or dynamic muscular strength.

Slacklining as therapy to address non-specific low back pain in the presence of multifidus arthrogenic muscle inhibition

Low back pain (LBP) represents the most prevalent, problematic and painful of musculoskeletal conditions that affects both the individual and society with health and economic concerns. LBP is a heterogeneous condition with multiple diagnoses and causes. In the absence of consensus definitions, partly because of terminology inconsistency, it is further referred to as non-specific LBP (NSLBP). In NSLBP patients, the lumbar multifidus (MF), a key stabilizing muscle, has a depleted role due to recognized myocellular lipid infiltration and wasting, with the potential primary cause hypothesized as arthrogenic muscle inhibition (AMI). This link between AMI and NSLBP continues to gain increasing recognition. To date there is no 'gold standard' or consensus treatment to alleviate symptoms and disability due to NSLBP, though the advocated interventions are numerous, with marked variations in costs and levels of supportive evidence. However, there is consensus that NSLBP management be cost-effective, self-administered, educational, exercise-based, and use multi-modal and multi-disciplinary approaches. An adjuvant therapy fulfilling these consensus criteria is 'slacklining', within an overall rehabilitation program. Slacklining, the neuromechanical action of balance retention on a tightened band, induces strategic indirect-involuntary therapeutic muscle activation exercise incorporating spinal motor control. Though several models have been proposed, understanding slacklining's neuro-motor mechanism of action remains incomplete. Slacklining has demonstrated clinical effects to overcome AMI in peripheral joints, particularly the knee, and is reported in clinical case-studies as showing promising results in reducing NSLBP related to MF deficiency induced through AMI (MF-AMI). Therefore, this paper aims to: rationalize why and how adjuvant, slacklining therapeutic exercise may positively affect patients with NSLBP, due to MF-AMI induced depletion of spinal stabilization; considers current understandings and interventions for NSLBP, including the contributing role of MF-AMI; and details the reasons why slacklining could be considered as a potential adjuvant intervention for NSLBP through its indirect-involuntary action. This action is hypothesized to occur through an over-ride or inhibition of central down-regulatory induced muscle insufficiency, present due to AMI. This subsequently allows neuroplasticity, normal neuro-motor sequencing and muscle re-activation, which facilitates innate advantageous spinal stabilization. This in-turn addresses and reduces NSLBP, its concurrent symptoms and functional disability. This process is hypothesized to occur through four neuro-physiological processing pathways: finite neural delay; movement-control phenotypes; inhibition of action and the innate primordial imperative; and accentuated corticospinal drive. Further research is recommended to investigate these hypotheses and the effect of slacklining as an adjuvant therapy in cohort and control studies of NSLBP populations.

Tensor Fascia Latae Muscle Structure and Activation in Individuals With Lower Limb Musculoskeletal Conditions: A Systematic Review and Meta-Analysis

BACKGROUND

Dysfunction of the tensor fascia latae (TFL) muscle is often clinically implicated in many musculoskeletal disorders.

OBJECTIVE

To systematically review the literature of the TFL muscle to determine whether there are differences in its structure and activation between individuals with and without lower limb musculoskeletal conditions.

DATA SOURCES

A comprehensive search in MEDLINE, EMBASE, CINHAL, and LILACS was undertaken from year of inception to 9 July 2019.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies that directly investigated the structure or activity of the TFL muscle between individuals with a lower limb musculoskeletal condition and a pain-free control group.

RESULTS

Seventeen studies were included (n = 556 participants), eight reporting structure and ten activation of the TFL muscle. Conditions included lateral hip pain, hip joint pathology, ACL injury, iliotibial band syndrome, and patellofemoral joint osteoarthritis. Meta-analysis identified with low confidence (p value = 0.07) a small tendency towards hypertrophy in the affected side of participants with hip joint diseases (SMD 0.37, 95% CI [- 0.02, 0.77]). Moderate effect sizes were found for a higher cross-sectional area of the TFL/sartorius ratio in abductor tendon tear (SMD 0.74; 95% CI [0.05, 1.43, p value = 0.04), and for a smaller body mass normalized TFL volume in patellofemoral joint osteoarthritis (SMD - 0.61; 95% CI [- 1.23, 0.00], p value = 0.05). Normalised electromyography (EMG) amplitude did not differ between groups for any condition, but when EMG was analysed as linear envelopes or synergies, some differences in pattern of TFL activation were observed between individuals with lateral hip pain and controls. Timing of TFL activation did not differ between individuals with knee conditions and controls.

CONCLUSIONS AND IMPLICATIONS

Common clinical assumptions of the role of TFL muscle in lower limb musculoskeletal conditions are not well investigated and poorly supported by current research. There are contradictory findings on the muscle size of TFL. Differing methodology in muscle activation studies precludes a clear interpretation for comparison between groups.

PROSPERO REGISTRATION NUMBER

CRD42017076160.

Pain and load progression following an early maximal strength training program in total hip- and knee arthroplasty patients

PURPOSE

Total hip arthroplasty (THA) and total knee arthroplasty (TKA) patients significantly increase muscle strength after maximal strength training (MST) initiated soon after surgery. Owing to severe postoperative pain, knee patients are anticipated to be more limited in performing heavy load exercises than hip patients. The aim of the present study was to describe pain and load progression during early MST in THA and TKA patients.

METHODS

Explorative study based on secondary analyses from two randomized controlled trials: 26 THA and 16 TKA patients had their training sessions logged. They trained at 85-90% of their maximal capacity in leg press, and abduction/knee-extension of the operated leg (4 × 5 repetitions) for 8-10 weeks, initiated early postoperatively.

RESULTS

Knee patients experienced significantly more pain than hip patients during the training sessions (p < 0.03), however, pain before and after training was not different (p > 0.09). All patients significantly increased leg press training load until the last intervention week (p < 0.01).

CONCLUSION

This study demonstrates that TKA patients experience more pain than THA patients during training following a MST program but not more than moderate levels during or after training. Pain before and after training is not different. Both groups significantly increased load progression during the intervention. These findings indicate that both THA and TKA patients might perform MST with extensive load progression early after surgery without compromising pain. The studies were registered at ClinicalTrials.gov .

A Randomized Controlled Trial of Eccentric Versus Concentric Cycling for Anterior Cruciate Ligament Reconstruction Rehabilitation

BACKGROUND

Persistent strength and biomechanical deviations remain after anterior cruciate ligament reconstruction (ACLR). Eccentric training may reduce these and associated reinjury or osteoarthritis risks.

HYPOTHESIS

For male patients who have undergone ACLR, eccentric training is more effective than concentric training at improving knee flexion angle and other biomechanical deviations, as well as strength and patient-reported outcomes, using a matched perceived exertion dose.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 26 men, 10-16 weeks after hamstring tendon graft ACLR, were randomized to an eccentric training group or a concentric control group. Both groups trained 3 times a week for 8 weeks using the same isokinetic cycle ergometer in a matched studio environment. Exercise dose was matched in training frequency, time, progression, and intensity using a target rating of perceived exertion. Baseline and follow-up testing included questionnaires, dynamometer strength testing, and walk/run gait analysis.

RESULTS

Eccentric training increased knee (+2.1°; P = .022) and hip (+2.1°; P = .010) flexion angles more than concentric training but not more than the minimal clinically important difference of 3°. Very large asymmetries in baseline knee abduction moment (walk, -0.10 N·m/kg/m; run, -0.54 N·m/kg/m) had not changed in either group by follow-up. Knee valgus angle effects were mixed. Tibial rotation angle increased in both groups, but concentric training was more effective at promoting symmetry (P < .001). Both groups had similar increases in affected limb quadriceps strength and knee flexion moments during walk/run gait (by 20% to 33%). Hamstring strength increased in the eccentric group (+15.4%) but not the concentric group. Eccentric group limb forces were 33% to 70% higher than those of the concentric group, with a lower heart rate. Both groups had low pain scores throughout.

CONCLUSION

For rehabilitation after ACLR, progressive eccentric cycle training was not more clinically effective than concentric training at a matched perceived intensity dose in male patients. This can guide exercise prescription for reducing gait and strength deviations of these patients.

REGISTRATION

PACTR201602001449365 (Pan African Clinical Trials Registry), NHREC 4344 (South African).

Arthrogenic muscle inhibition and return to sport after arthrofibrosis complicating anterior cruciate ligament surgery

Arthrofibrosis is a devastating complication after Anterior Cruciate Ligament reconstruction (ACLr) characterized by a muscle weakness secondary to an arthrogenic muscle inhibition process. The loss of knee isokinetic strength due to arthrogenic muscle inhibition may be more important after arthrofibrosis, compared to an ACLr population with no complication. The isokinetic strength deficit [Limb Symmetry Index (LSI) at 60 and 180°/s of angular speed] was measured at 4, 7 and 12 post-operative months. Knee function, return to running and return to sport were evaluated. A comparison of the Quadriceps and the Hamstring LSI between patients with arthrofibrosis and those without post-operative complication was performed according to time and taking into consideration the type of surgical procedure. 539 primary ACLr patients were assessed. The arthrofibrosis group presented at 4, 7 and 12 post-operative months a Quadriceps LSI significantly lower compared to the control group, without influence of the graft procedure (LSI: 38, 53, 68% vs 63, 73, 85% at 60°/s, respectively). The Hamstring LSI was significantly lower at 4 and 7 post-operative months, but comparable at 12 months with an influence of the Hamstring procedure. Knee function was significantly lower at 4 and 7 post-operative months. Few arthrofibrosis ACLr patients returned to running at 7 post-operative months (6.8% vs 69.9%; p < .0001). An important and durable Quadriceps muscle weakness occurred after arthrofibrosis, whatever the type of graft procedure. This is explained by an Arthrogenic muscle inhibition which compromised the return to sport at the same level until 12 post-operative months. HighlightsAn important and durable quadriceps muscle weakness occurred after arthrofibrosis.The arthrogenic muscle inhibition was significant on the operated side independently of the type of the graft procedure.Arthrogenic muscle inhibition compromised the return to sport at the same level until 12 post-operative months.

Promising Effect of Visually-Assisted Motor Imagery Against Arthrogenic Muscle Inhibition - A Human Experimental Pain Study

Purpose

Clinically, arthrogenic muscle inhibition (AMI) has a negative impact on functional recovery in musculoskeletal disorders. One possible technique to relieve AMI is motor imagery, which is widely used in neurological rehabilitation to enhance motor neuron excitability. The purpose of this study was to verify the efficacy of visually-assisted motor imagery against AMI using a human experimental pain model.

Methods

Ten healthy volunteers were included. Experimental ankle pain was induced by hypertonic saline infusion into unilateral Kager’s fat pad. Isotonic saline was used as control. Subjects were instructed to imagine while watching a movie in which repetitive motion of their own ankle or fingers was shown. H-reflex normalized by the motor response (H/M ratio) on soleus muscle, maximal voluntary contraction (MVC) force of ankle flexion, and contractile activities of the calf muscles during MVC were recorded at baseline, pre-intervention, post-intervention, and 10 minutes after the pain had subsided.

Results

Hypertonic saline produced continuous and constant peri-ankle pain (VAS peak [median]= 6.7 [2.1–8.4] cm) compared to isotonic saline (0 [0–0.8] cm). In response to pain, there were significant decreases in the H/M ratio, MVC and contractile activities (P<0.01), all of which were successfully reversed after the ankle motion imagery. In contrast, no significant changes were observed with the finger motion imagery.

Conclusion

Visually-assisted motor imagery improved the pain-induced AMI. Motor imagery of the painful joint itself would efficiently work for relieving AMI. This investigation possibly shows the potential of a novel and versatile approach against AMI for patients with musculoskeletal pain.

Assessment of Quadriceps Corticomotor and Spinal-Reflexive Excitability in Individuals with a History of Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

BACKGROUND

Differences in the excitability of motor generating neural pathways are reported following anterior cruciate ligament reconstruction (ACLR) that is associated with quadriceps dysfunction and theorized to prevent the full recovery of muscle function.

OBJECTIVE

The aims of this systematic review and meta-analysis were to compare quadriceps neural excitability between the involved ACLR limb, the uninvolved limb, and uninjured controls, and to determine at what time intervals these differences are present after surgery.

METHODS

We conducted a search of PubMed, SPORTDiscus, Embase, and Web of Science, and extracted measures assessing difference of quadriceps spinal-reflexive, corticospinal, and intracortical excitability from studies that compared (1) involved limb to the uninvolved limb, (2) involved limb to a control limb, or (3) uninvolved limb to a control limb. We stratified time at 24 months, since this represents a period of heightened risk for reinjury. A modified Downs and Black checklist and Egger's test were used to determine the methodological quality of individual studies and risk of bias between studies.

RESULTS

Fourteen studies comprising 611 participants (371 individuals with a history of ACLR; median time from surgery: 31.5 months; range 0.5-221.1 months) were included in the review. Overall, the involved (g = 0.60, 95% CI [0.24, 0.96]) and uninvolved (g = 0.49, 95% CI [0.00, 0.98]) limbs exhibited greater motor threshold (MT) in comparison to uninjured controls. Motor-evoked potential (MEP) amplitudes were greater in the uninvolved limb in comparison to uninjured controls (g = 0.31, 95% CI [0.03, 0.59]). Lesser intracortical inhibition was exhibited in the uninvolved limb compared to uninjured controls (g = 0.54, 95% CI [0.14, 0.93]). When stratified by time from surgery, MEP amplitudes were greater in the uninvolved limb compared to uninjured controls (g = 0.33, 95% CI [0.03, 0.63]) within the first 24 months after surgery. When evaluated more than 24 months after surgery, the involved limb exhibited greater Hoffmann reflex (H-reflex) compared to uninjured controls (g = 0.38, 95% CI [0.00, 0.77]). MT were greater in the involved limb (g = 0.93, 95% CI [- 0.01, 1.88]) and uninvolved limb (g = 0.57, 95% CI [0.13, 1.02]) compared to uninjured controls. MEP amplitudes in the involved limb were lesser compared to uninjured controls when evaluated more than 24 months after ACLR (g = -1.11, 95% CI [- 2.03, - 0.20]).

CONCLUSIONS

The available evidence supports that there are neural excitability differences within the corticospinal tract in individuals with ACLR when compared to uninjured controls. Future research should focus further on longitudinal assessments of neural excitability prior to and following ACLR. Identifying interventions aimed to facilitate corticospinal excitability after ACLR appears to be warranted to improve quadriceps function.

TRIAL REGISTRATION

Registered through PROSPERO CRD42020158714.

Gamma Loop Dysfunction as a Possible Neurophysiological Mechanism of Arthrogenic Muscle Inhibition: A Narrative Review of the Literature

Context: Quadriceps activation failure has been observed following various pathological conditions in a knee joint such as knee surgery, pain, effusion in knee, and osteoarthritis also could be aging matter. Those patients are unable to attain maximal quadriceps strength for a long period of time although their quadriceps itself is not damaged. This impairment is termed arthrogenic muscle inhibition (AMI). AMI has been of concern to clinicians because this weakness hinders the rehabilitation process considerably and delays recovery because strengthening protocols for the AMI could be largely ineffective. Clinically, it is important to understand neurophysiological mechanisms of the AMI to treat patients with the impairment. Objectives: This is a narrative review of the literature. The purpose of this review is to understand the following: (1) Why investigations of only peripheral spinal reflexive pathways are not enough for elucidation of the mechanisms of the AMI? (2) What we know about the role of the gamma spindle system in AMI so far? (3) Could a dysfunctional gamma spindle system contribute to AMI lead neural changes in upper central nervous system? and (4) Concerns that a clinician should take into consideration when deciding whether to apply therapeutic interventions for AMI. Data Sources: The databases PubMed, MEDLINE, SPORTDiscus, and CINAHL were searched with the terms arthrogenic muscle inhibition (AMI), reflex inhibition, joint mechanoreceptor, gamma loop, corticospinal pathway, spinal reflex, effusion, and joint injury. The remaining citations were collected from references of similar papers. Conclusions: AMI is a limiting factor in the rehabilitation of joint injury. Motor unit recruitment could be hindered in patients with AMI as a result of a dysfunctional gamma spindle system. Clinicians should understand the mechanism of AMI well in order to establish effective rehabilitation programs for AMI. Indeed, AMI is not caused by a single factor, but rather, multiple neural factors can change over time following the appearance of AMI. Therefore, multiple interventions targeting different neural pathways should be combined to achieve the ideal therapeutic goal for the treatment of AMI.

Athletes with an ACL reconstruction show a different neuromuscular response to environmental challenges compared to uninjured athletes

BACKGROUND

Evidence suggests that neuromuscular alterations in patients with an anterior cruciate ligament reconstruction (ACLR) are rooted in neurocognitive and proprioceptive deficits. The aim of this study was to assess neuromuscular control of athletes with ACLR under increased cognitive and environmental challenges.

RESEARCH QUESTION

Do athletes with ACLR show a different neuromuscular response to cognitive and environmental challenges relative to controls?

METHODS

Cross-sectional study. Twenty athletes who had an ACLR (age: 23.7 ± 4.3 years, 14 males, time post-surgery: 258.6 ± 54 days) and twenty uninjured controls (age: 21.4 ± 1.5 years, 14 males) performed a stepping down-task in four environmental conditions: no additional challenges, while performing a cognitive dual-task, while undergoing an unpredictable support surface perturbation, and with the cognitive dual-task and unpredictable perturbation combined. Muscle activations of the vastus medialis (VM), vastus lateralis, hamstrings medialis (HM), hamstrings lateralis (HL), gastrocnemius medialis, gastrocnemius lateralis (GL) and gluteus medius were recorded with surface EMG. A three-way ANOVA with main effects for group, dual-task and perturbation was used to compare muscle activations.

RESULTS

Athletes with ACLR show larger HM (ES = 0.45) and HL activation (ES = 1.32) and lower VM activation (ES = 0.72), compared to controls. Athletes with ACLR show a significantly smaller increase in VM (ES = 0.69), VL (ES = 0.53) and GL activation (ES = 0.52) between perturbed and unperturbed tasks compared to controls. Furthermore, under cognitive loading a significantly larger decrease in HM activation (ES = 0.40) and (medial) co-contraction (ES = 0.75) was found in athletes with ACLR compared to controls.

SIGNIFICANCE

Athletes with ACLR show an altered neuromuscular response which might represent an arthrogenic muscle response. They show less additional adaptation to perturbed tasks compared to controls, potentially as result of altered proprioceptive input. Furthermore a larger influence of increased cognitive loading on the neuromuscular control was found in athletes with ACLR, indicating that also neurocognitive limitations may contribute to altered neuromuscular control.

Using neuromuscular electrical stimulation in conjunction with ultrasound imaging technique to investigate lumbar multifidus muscle activation deficit

Lumbar multifidus muscle (LM) activation deficit has been proposed as a potential underlying mechanism responsible for recurrence episode of low back pain (LBP). The quantification of voluntary LM activation can provide a better understanding of the role of muscle activation deficit in LBP. The objective of this technical report is to propose a new approach using neuromuscular electrical stimulation (NMES) in combination with the ultrasound imaging technique (USI) to investigate the ability of individual to voluntarily activate the LM. We recruited ten participants with a recurrent LBP (rLBP) and twelve participants with no history of LBP (NoLBP). Theoretically, the superimposition of NMES on the LM during maximum voluntary isometric contraction (MVIC) should activate all motor units available in the LM. The percentage of LM activation (%LM) can be calculated by the changes of LM thickness during MVIC, divided by the changes of LM thickness during the combination of MVIC and NMES. This %LM was used to compare between groups. The individuals with rLBP had significantly lower %LM (p < 0.05) compared with the NoLBP counterpart (%LM = 72.4 and 92.9, respectively). Results demonstrate that this new approach can potentially differentiate %LM among individuals with rLBP and NoLBP. This new approach can be potentially used to 1) determine the extent of LM activation deficit, 2) identify the existence of muscle activation deficit in the LM, and 3) objectively measure the effect of the intervention designed to address the LM activation deficit.

Impaired Regulation of Submaximal Force after ACL Reconstruction: Role of Muscle Spindles

Ongoing motor deficits are routinely present following anterior cruciate ligament (ACL) reconstruction, including the ability to regulate muscle force. While such deficits are known, it is unclear why this occurs. The goal of the current study was to investigate the potential influence of muscle spindle input on submaximal force regulation and muscle activity at the knee in people following ACL reconstruction. Fourteen participants (8 female) who were 6-24 months post-ACL reconstruction and 15 control participants (8 female) undertook submaximal force matching and force modulation tasks before and after 20 min of vibration applied to the patella tendon. Across all tasks, the ACL reconstruction participants were poorer at force matching (P=0.007). The effect of vibration was not significant in either group for the force matching tasks (P=0.06), although there was a reduction in maximum voluntary contraction post-vibration in the control group (P<0.001). The ACL reconstruction group also showed evidence of greater activation of the medial hamstring muscles in comparison to controls (P=0.04). Individuals who have undergone ACL reconstruction have a diminished ability to accurately match and regulate submaximal muscle force, but this does not appear to be related to impaired muscle spindle input. Neuromuscular retraining programs that involve force regulation tasks may be necessary to optimize rehabilitation after ACL reconstruction.

The relationship between prescribed pre-operative knee-extensor exercise dosage and effect on knee-extensor strength prior to and following total knee arthroplasty: a systematic review and meta-regression analysis of randomized controlled trials

OBJECTIVE

The aim of this systematic review was to evaluate the relationship between prescribed knee-extensor strength exercise dosage in pre-operative exercise intervention and the effect on knee-extensor muscle strength prior to and following TKA. Additional meta-analyses report the effect of pre-habilitation on outcomes prior to and following TKA.

DESIGN

A systematic literature search was performed including RCT's evaluating the effect of pre-operative exercise prior to and following TKA. Meta-regression analysis was performed to evaluate the dose-response relationship between prescribed exercise dose and the pooled effect, measured as standardized mean difference (SMD). The prescribed exercise dose was quantified using a formula accounting for as many exercise descriptors as possible. Risk of bias in the included trials was assessed using the Cochrane Risk of Bias Tool.

RESULTS

Twelve trials with 616 patients were included. Meta-regression analysis showed no relationship between prescribed pre-operative knee-extensor exercise dosage and change in knee-extensor strength neither prior to (slope 0.0005 [95%CI -0.007 to 0.008]) or 3 months following TKA (slope 0.0014 [95%CI -0.006 to 0.009]). Prior to TKA, a moderate effect favoring pre-operative exercise for increase in knee-extensor strength was found (SMD 0.50 [95%CI 0.12 to 0.88]), but not at 3 months following TKA (SMD -0.01 [95%CI -0.45 to 0.43]). Risk of bias was generally assessed as unclear.

CONCLUSION

Meta-regression analysis of existing trials suggests no relationship between the prescribed pre-operative knee-extensor exercise dosage and the change in knee-extensor strength observed prior to and following TKA. Pre-operative exercise including knee-extensor muscle strength exercise increased knee-extensor strength moderately prior to but not 3 months following TKA.

PROTOCOL REGISTRATION

PROSPERO ID (CRD42018076308) (http://www.crd.york.ac.uk/PROSPERO/).

The Immediate Effects of Transcranial Direct Current Stimulation on Quadriceps Muscle Function in Individuals With a History of Anterior Cruciate Ligament Reconstruction: A Preliminary Investigation

CONTEXT

Altered quadriceps activation is common following anterior cruciate ligament reconstruction (ACLR), and can persist for years after surgery. These neural deficits are due, in part, to chronic central nervous system alterations. Transcranial direct current stimulation (tDCS) is a noninvasive modality, that is, believed to immediately increase motor neuron activity by stimulating the primary motor cortex, making it a promising modality to use improve outcomes in the ACLR population.

OBJECTIVE

To determine if a single treatment of tDCS would result in increased quadriceps activity and decreased levels of self-reported pain and dysfunction during exercise.

DESIGN

Randomized crossover design.

SETTING

Controlled laboratory.

PATIENTS

Ten participants with a history of ACLR (5 males/5 females, 22.9 [4.23] y, 176.57 [12.01] cm, 80.87 [16.86] kg, 68.1 [39.37] mo since ACLR).

INTERVENTIONS

Active tDCS and Sham tDCS.

MAIN OUTCOME MEASURES

Percentage of maximum electromyographic data of vastus medialis and lateralis, voluntary isometric strength, percentage of voluntary activation, and self-reported pain and symptom scores were measured. The 2 × 2 repeated-measures analysis of variance by limb were performed to explain the differences between time points (pre and post) and condition (tDCS and sham).

RESULTS

There was a significant time main effect for quadriceps percentage of maximum electromyographic of vastus medialis (F9,1 = 11.931, P = .01) and vastus lateralis (F9,1 = 9.132, P = .01), isometric strength (F9,1 = 5.343, P = .046), and subjective scores for pain (F9,1 = 15.499, P = .04) and symptoms (F9,1 = 15.499, P = .04). Quadriceps percentage of maximum electromyographic, isometric strength, and voluntary activation showed an immediate decline from pre to post regardless of tDCS condition. Subjective scores improved slightly after each condition.

CONCLUSIONS

One session of active tDCS did not have an immediate effect on quadriceps activity and subjective scores of pain and symptoms. To determine if tDCS is a valid modality for this patient population, a larger scale investigation with multiple treatments of active tDCS is warranted.

Relationship between pre- and post-operative isokinetic strength after ACL reconstruction using hamstring autograft

BACKGROUND

Anterior cruciate ligament (ACL) ruptures are of major concern in sports. As mostly young and active individuals are affected there is an emphasis on the rapid and safe return to sports (RTS). Strengthening the ventral and dorsal thigh muscles is a prerequisite for a successful RTS after ACL reconstruction (ACLR), as persistent muscle weakness may increase the incidence for secondary injuries and impair performance. Aiming to increase evidence on the importance of preoperative muscle strength and the coaching of patients, the purpose of this study is to compare thigh muscle strength pre- and post-operatively after ACLR.

METHODS

We performed a retrospective analysis of 80 patients with primary, isolated ACLR using a four-stranded hamstring autograft. We performed bilateral isokinetic concentric strength measurement (60°/s) before and six months after ACLR. Primary outcomes were the maximal knee extension and flexion torque, hamstrings-to-quadriceps ratio (H/Q ratio) and the corresponding limb symmetry indices (LSI). Pearson correlations were calculated for pre- and post-surgical values.

RESULTS

The operated as well as the unaffected leg increased maximal knee extension (+ 18% ± 7% p < 0.05; + 11% ± 5% p < 0.05) and flexion torque (+ 9% ± 5% p < 0.05, + 10% ± 6% p < 0.05) throughout the 6 months of rehabilitation. The H/Q ratio remained unaffected (- 2% ± 3% p = 0.93; - 4% ± 4% p = 0.27). LSI of knee extension strength increased significantly (6% ± 3% p < 0.05), while flexion strength remained unaffected (+ 2% ± 4% p = 0.27). Positive correlations underline the interrelationship between the strength pre- and post-surgery for the knee extension (r = 0.788 p < 0.05) and knee flexion strength (r = 0.637 p < 0.05) after ACLR.

CONCLUSIONS

Preoperative leg extension and flexion strength normalized to body mass are strongly correlated to postoperative strength performance after ACLR. Therefore, pre-operative quadriceps and hamstring muscle strength deficits may have a significant negative impact on functional performance following ACLR. This emphasizes the need for intensive preoperative screening and subsequent treatment to achieve the best possible preoperative leg strength before ACLR.

TRIAL REGISTRATION

DRKS00020210 .

Knee Kinetics in Baseball Hitting and Return to Play after ACL Reconstruction

The purpose of this study was to describe the knee kinetics of baseball hitting, develop a tool to predict knee kinetics from easily obtainable measures, and to compare knee kinetics to other exercises along the rehabilitation continuum to determine a timeline for when hitting may resume after ACL reconstruction. Nineteen high school baseball athletes (16.3±0.8 yrs, 180.6±5.7 cm, 78.4±10.8 kg) participated. Participants took ten swings off a tee. Kinetic data were recorded using an electromagnetic tracking system. Data from swings with the top three exit velocities were averaged for analysis. Linear regressions were used to determine if predictors of height, mass, age and exit velocity could predict the following torques: bilateral knee net, extension, internal and external rotation, valgus and varus torque; and anterior force. Backwards regression models revealed independent variables could significantly predict front knee net, internal and external rotation, extension, and varus torque, and anterior force; and back knee net and valgus torque. Based on the kinetics of baseball hitting compared to those of rehabilitation exercises, if the involved knee is the front, we suggest tee hitting may be initiated at 13 weeks after ACL reconstruction. If the involved knee is the back, we suggest tee hitting may initiated at 17 weeks after ACL reconstruction.

Single bout of vibration-induced hamstrings fatigue reduces quadriceps inhibition and coactivation of knee muscles after anterior cruciate ligament (ACL) reconstruction

Persistent quadriceps strength deficits in individuals with anterior cruciate ligament reconstruction (ACLr) have been attributed to arthrogenic muscle inhibition (AMI). The purpose of the present study was to investigate the effect of vibration-induced hamstrings fatigue on AMI in patients with ACLr. Eight participants with unilateral ACLr (post-surgery time: M = 46.5, SD = 23.5 months; age: M = 21.4, SD = 1.4 years) and eight individuals with no previous history of knee injury (age: M = 22.5, SD = 2.5 years) were recruited. A fatigue protocol, consisting of 10 min of prolonged local hamstrings vibration, was applied to both the ACLr and control groups. The central activation ratio (CAR) of the quadriceps was measured with a superimposed burst of electrical stimulation, and hamstrings/quadriceps coactivation was assessed using electromyography (EMG) during isometric knee extension exercises, both before and after prolonged local vibration. For the ACLr group, the hamstrings strength, measured by a load cell on a purpose-built chair, was significantly (P = 0.016) reduced about 14.5%, indicating fatigue was actually induced in the hamstrings. At baseline, the ACLr group showed a trend (P = 0.051) toward a lower quadriceps CAR (M = 93.2%, SD = 6.2% versus M = 98.1%, SD = 1.1%) and significantly (P = 0.001) higher hamstrings/quadriceps coactivation (M = 15.1%, SD = 6.2% versus M = 7.5%, SD = 4.0%) during knee extension compared to the control group. The fatigue protocol significantly (P = 0.001) increased quadriceps CAR (from M = 93.2%, SD = 6.2% to M = 97.9%, SD = 2.8%) and significantly (P = 0.006) decreased hamstrings/quadriceps coactivation during knee extension (from M = 15.1%, SD = 6.2% to M = 9.5%, SD = 4.5%) in the ACLr group. In conclusion, vibration-induced hamstrings fatigue can alleviate AMI of the quadriceps in patients with ACLr. This finding has clinical implications in the management of recovery for ACLr patients with quadriceps strength deficits and dysfunction.

Type of measurement used influences central and peripheral contributions to quadriceps weakness after anterior cruciate ligament (ACL) reconstruction

OBJECTIVE

The relative contribution of muscle size and voluntary activation (VA) on quadriceps strength after anterior cruciate ligament (ACL) reconstruction remains inconclusive. Here, we aimed to determine the contributions of muscle size and VA on quadriceps strength in ACL-reconstructed patients and determine if contributions were similar if unilateral outcomes (i.e. ACL-reconstructed limb) or the LSI was used.

DESIGN

A cross-sectional study.

SETTING

A university research laboratory.

PARTICIPANTS

Sixteen individuals 6-12 months after ACL reconstruction (Age: 22.3 ± 6.0yr, Height: 1.7 ± 0.1 m, Mass: 68.7 ± 11.5 kg) were recruited.

MAIN OUTCOME MEASURES

Quadriceps isometric strength and VA, via the interpolated triplet technique, were assessed bilaterally. Ultrasound images were acquired of the vastus lateralis to calculate cross-sectional area (CSA) in both legs. LSI's were computed for all variables by expressing values of the reconstructed leg as a percent of the non-reconstructed leg. Separate stepwise linear regressions were performed to examine the contribution of VA and CSA on quadriceps strength. Model 1 used LSI for all outcomes and model 2 used outcomes from the reconstructed leg.

RESULTS

We observed between limb deficits of 27.78% in quadriceps strength, 13.61% in vastus lateralis CSA, and 13.18% in VA (P < 0.05). Strength LSI was significantly predicted by VA LSI (R² = 0.45, P < 0.01), but not by CSA LSI (R² = 0.01, P =0.87). Reconstructed leg strength was significantly predicted by VL CSA (R² = 0.50, P < 0.01) but not quadriceps VA (R² = 0.08, P =0.11).

CONCLUSIONS

The contributions of VA and CSA on quadriceps PT differed greatly if LSI or reconstructed leg outcomes were used. Evaluation of VA and CSA in unison may be provide a more holistic understanding of the sources of muscle weakness after ACL reconstruction.

Comparison of muscle activation levels and knee valgus between individuals with medial patellofemoral ligament reconstruction and healthy individuals during fatiguing step down task

BACKGROUND

Medial patellofemoral ligament reconstruction becomes first-choice surgical procedure for patients with a history of lateral patellar dislocations but there is limited knowledge about neuromuscular activation patterns of individuals with a history of patellar dislocation who underwent medial patellofemoral ligament reconstruction.

OBJECTIVE

The aim of this study was to compare muscle activation levels and knee valgus during step down performance test between individuals with a history of medial patellofemoral ligament reconstruction and healthy individuals.

METHODS

Fifteen individuals with medial patellofemoral ligament reconstruction and 15 healthy individuals were included. Vastus medialis obliquus, vastus lateralis and gluteus medius muscle activation levels and knee valgus were measured during 60-s- step down performance test. Two-way repeated-measures of analysis of covariance was used for statistical analysis.

FINDINGS

Compared to the healthy individuals, individuals with medial patellofemoral ligament reconstruction showed lower vastus medialis obliquus (p = .04) and gluteus medius (p = .005) activation levels, and higher knee valgus (p = .002) in last period of the step down performance test.

INTERPRETATION

Since the significant results were only observed in the fatiguing section of the test, endurance tests may provide more information about neuromuscular control of the individuals with history of medial patellofemoral ligament reconstruction. Future studies should investigate whether endurance exercises that target to improve vastus medialis obliquus and gluteus medius activity result in better clinical outcomes than conventional programs for individuals with medial patellofemoral ligament reconstruction.

Strength and Power Training in Rehabilitation: Underpinning Principles and Practical Strategies to Return Athletes to High Performance

Injuries have a detrimental impact on team and individual athletic performance. Deficits in maximal strength, rate of force development (RFD), and reactive strength are commonly reported following several musculoskeletal injuries. This article first examines the available literature to identify common deficits in fundamental physical qualities following injury, specifically strength, rate of force development and reactive strength. Secondly, evidence-based strategies to target a resolution of these residual deficits will be discussed to reduce the risk of future injury. Examples to enhance practical application and training programmes have also been provided to show how these can be addressed.

A Randomized Controlled Pilot Study Comparing the Efficacy of Pulsed Radiofrequency Combined With Exercise Versus Exercise Alone in Pain Relief and Functional Improvement for Chronic Knee Osteoarthritis

OBJECTIVES

To compare the long-term efficacy between pulsed radiofrequency (PRF) combined with passive stretching (PRF-PS) exercise and PS exercise alone in reducing pain and improving quadriceps muscle strength and knee function.

METHODS

Sixty-two participants were randomly assigned with a 1:1 allocation to the PRF-PS exercise group or the PS exercise group. Level of pain, muscle strength, and knee function were assessed from baseline to the first, third, and sixth months after treatment using the VAS, peak torque (PT), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), respectively.

RESULTS

There were no significant differences at baseline between the 2 groups. Compared to exercise alone, participants achieved superior efficacy with PRF-PS in pain relief, improvement of muscle strength, and knee function. Moreover, the improvement of all variables was maintained for a longer period of time in the PRF-PS group. The reduction in participants' VAS pain intensity scores was superior for PRF-PS vs. PS with overall estimation (adjusted mean difference: -1.85 cm; 95% confidence interval [CI] -2.25, -1.45 cm; P = 0.000). The increase in participants' PT scores was superior for PRF-PS vs. PS with overall estimation (adjusted mean difference: 15.53 N. m; 95% CI 7.07, 23.98 N. m; P = 0.000; and 12.62 N. m; 95% CI 0.96, 24.28 N. m; P = 0.000 for PT 60 degrees/s and PT 180 degrees/s, respectively). The reduction in participants' WOMAC scores was superior for PRF-PS vs. PS with overall estimation (adjusted mean difference: -16.43; 95% CI -22.22, -10.64; P = 0.000).

DISCUSSION

The improvement in pain relief and knee function might be associated with restoration of muscle strength after PRF-PS exercise by overcoming muscle inhibition.

Skeletal Muscle Disuse Atrophy and the Rehabilitative Role of Protein in Recovery from Musculoskeletal Injury

Muscle atrophy and weakness occur as a consequence of disuse after musculoskeletal injury (MSI). The slow recovery and persistence of these deficits even after physical rehabilitation efforts indicate that interventions designed to attenuate muscle atrophy and protect muscle function are necessary to accelerate and optimize recovery from MSI. Evidence suggests that manipulating protein intake via dietary protein or free amino acid-based supplementation diminishes muscle atrophy and/or preserves muscle function in experimental models of disuse (i.e., immobilization and bed rest in healthy populations). However, this concept has rarely been considered in the context of disuse following MSI, which often occurs with some muscle activation during postinjury physical rehabilitation. Given that exercise sensitizes skeletal muscle to the anabolic effect of protein ingestion, early rehabilitation may act synergistically with dietary protein to protect muscle mass and function during postinjury disuse conditions. This narrative review explores mechanisms of skeletal muscle disuse atrophy and recent advances delineating the role of protein intake as a potential countermeasure. The possible synergistic effect of protein-based interventions and postinjury rehabilitation in attenuating muscle atrophy and weakness following MSI is also considered.

Is Pre-operative Quadriceps Strength a Predictive Factor for the Outcomes of Anterior Cruciate Ligament Reconstructions

Persistent quadriceps weakness prevents patients from returning to sports after ACL reconstruction. Pre-operative quadriceps strength was indicated as an important factor for the outcomes of ACL reconstruction. However, the existing evidence is controversial. Therefore, this systematic review was conducted to summarize and evaluate the relationship between pre-operative quadriceps strength and the outcomes following ACL reconstruction, and to summarize the predictive value of pre-operative quadriceps strength for satisfactory post-operative outcomes. Pubmed, WOS, Embase, CINAHL and SportDiscus were searched to identify eligible studies according to PRISMA guidelines. Relevant data was extracted regarding quadriceps strength assessment methods, pre-operative quadriceps strength, participants treatment protocols, post-operative outcomes, follow-up time points and the relevant results of each individual study. Twelve cohort studies (Coleman methodology score: 62±10.4; from 44-78) with 1773 participants included. Follow-up period ranged from 3 months to 2 years. Moderate evidence supports the positive association between pre-operative quadriceps strength and post-operative quadriceps strength; weak evidence supports the positive association between pre-operative quadriceps strength and post-operative functional outcomes. By now, there is no consensus on the predictive value of pre-operative quadriceps strength for achieving satisfactory quadriceps strength after ACLR. To conclude, pre-operative quadriceps strength should be taken into consideration when predict patient recovery of ACLR.

The immediate effects of passive hip joint mobilization on hip abductor/external rotator muscle strength in patients with anterior knee pain and impaired hip function. A randomized, placebo-controlled crossover trial

Background: Anterior knee pain (AKP) is often associated with persistent hip muscle weakness and facilitatory interventions may be beneficial for managing patients with AKP (pwAKP). Physiotherapists often employ passive oscillatory hip joint mobilizations to increase hip muscle function. However, there is little information about their effectiveness and the mechanisms of action involved. Objectives: To investigate the immediate effects of passive hip joint mobilization on eccentric hip abductor/external rotator muscle strength in pwAKP with impaired hip function. Design: A double-blinded, randomized, placebo-controlled crossover design. Method: Eighteen patients with AKP participated in two sessions of data collection with one week apart. They received passive hip joint mobilization or placebo mobilization in a randomized order. Eccentric hip muscle strength was measured immediately before and after each intervention using a portable hand-held dynamometer. Results: An ANCOVA with the sequence of treatment condition as the independent variable, the within-subject post-treatment differences as the dependent variable and the within-subject pre-treatment differences as the covariate was conducted. Patients showed a significant mean increase in eccentric hip muscle strength of 7.73% (p = 0.001) for the mobilization condition, compared to a mean decrease of 4.22% for the placebo condition. Seventeen out of eighteen participants reported having no pain during any of the strength testing. Conclusion: These data suggest that passive hip joint mobilization has an immediate positive effect on eccentric hip abductor/external rotator muscle strength in pwAKP with impaired hip function, even in the absence of current pain.

Isokinetic Strength Test of Muscle Strength and Motor Function in Total Knee Arthroplasty

Objective

To use isokinetic strength testing system to test and analyze the relationship between changes in muscle strength before and after knee replacement in patients undergoing total knee arthroplasty (TKA).

Methods

A total of 200 patients with advanced knee osteoarthritis treated from June 2018 to June 2019 were selected for TKA. The patient's isokinetic muscle strength test was performed in the first, third, and the sixth month before and after the operation. The knee hamstring peak torque (PT value), quadriceps peak torque (PT value), and total work were mainly measured. The knee joint was evaluated at the hospital for special surgery score, range of motion and other knee function standards, and then healthy limbs and normal people were tested with the same method. Statistical data was used to analyze and deal with the data, evaluate the muscle strength and motor function changes with time progressing, then compare the differences to the healthy limb. From P < 0.05, we can see that the differences have some statistical significance. The influences that TKA has on motor function changes of lower limbs were also observed.

Results

Among the 200 subjects, 162 completed all follow‐up tests, and the remaining 38 were lost to follow‐up for various reasons. The rate of loss of follow‐up was approximately 19%. The isokinetic muscle strength test system and the knee joint function scoring standard were used to record the knee joint muscle strength and function changes before and after knee joint replacement. Statistical analysis was performed to show the knee joint hamstring muscle force and quadriceps muscle strength and joint mobility in the first month after the surgery. The knee joint muscle strength and joint mobility were significantly improved after the third month after the surgery, but there were still some differences compared with normal people. The knee function index was significantly improved in the sixth month after operation (P < 0.05), and there were no significant differences compared with normal people.

Conclusions

Knee joint strength and knee function after TKA are significantly improved compared with preoperative function, which is of great significance for the treatment of knee osteoarthritis. The constant velocity muscle strength test system has the advantages of safety, accuracy, repeatability and easy operation. It is a good method to evaluate the knee joint's muscle strength and function after the knee joint replacement.

Thigh musculature stiffness during active muscle contraction after anterior cruciate ligament injury

Background

Altered motor unit (MU) activity has been identified after anterior cruciate ligament (ACL) injury, but its effect on muscle tissue properties is unknown. The purpose of this study was to compare thigh musculature muscle stiffness between control and ACL-injured subjects.

Methods

Thirty ACL-injured subjects and 25 control subjects were recruited. Subjects completed a randomized protocol of isometric contractions while electromyography (EMG) signals were recorded. Three maximum voluntary isometric contractions (MVIC) determined peak force for 10 and 25% MVIC trials. Shear wave elastography was captured during each 10 and 25% MVIC trials.

Results

Differences in muscle stiffness were assessed between limbs and groups. 12 months post-surgery had higher stiffness for VM 0% MVIC, VL 0 and 10% MVIC, and ST 10 and 25% MVIC (all p ≤ 0.04).

Conclusion

Thigh musculature stiffness changed throughout rehabilitation and remained altered at 12 months after ACL reconstruction.

Biofeedback Core Exercise Using Hybrid Assistive Limb for Physical Frailty Patients With or Without Parkinson's Disease

Introduction: Elderly people often exhibit "frailty," and motor dysfunction occurs. Several studies have reported about the relationship between motor dysfunction and frailty in Parkinson's disease (PD). This study aimed to test whether the core exercise using the hybrid assistive limb lumbar type for care support (HAL-CB02) may improve the motor functions in frailty patients with or without PD and to explore the optimal patient selection from the frailty cohort. Materials and Methods: We recruited 16 frailty patients (PD = 8; non-PD = 8). The participants performed core exercise and squats using HAL-CB02 for five sessions a week. Outcome measures were 10-m walking test, step length, timed up-and-go test, 30-s chair stand test, and visual analog scale. Evaluation was conducted at baseline, post-exercise, and 1- and 3-month follow-ups. Results: Both PD and non-PD patients showed significant improvement in all evaluation items post-exercise. Moreover, no significant difference was found in the improvement value between the two groups. Conclusions: Our results suggest that biofeedback exercise with HAL-CB02 is a safe and promising treatment for frailty patients. Motor dysfunction in PD patients may be partly due to physical frailty, and biofeedback exercise with HAL-CB02 is proposed as a treatment option.