Effects of early progressive eccentric exercise on muscle size and function after anterior cruciate ligament reconstruction: a 1-year follow-up study of a randomized clinical trial

The Nature of Rehabilitation Programs to Improve Musculoskeletal, Biomechanical, Functional, and Patient-Reported Outcomes in Athletes With ACL Reconstruction: A Scoping Review

CONTEXT

After anterior cruciate ligament (ACL) reconstruction (ACLR), athletes commonly undergo prolonged rehabilitation (eg, 9-12 months), but few actually return to preinjury sports activities. The nature (composition, configuration) of an ACL rehabilitation program (ACL-RP) is an important factor in determining rehabilitation outcomes; however, details about the nature of ACL-RPs are reported inconsistently in research studies. To guide future research reporting to support clinical translation and implementation of ACL-RPs, it is necessary to describe the nature, reporting, and outcomes of ACL-RPs in the current literature.

OBJECTIVE

The purpose of this scoping review was to understand the nature and reporting of various ACL-RPs that address musculoskeletal, biomechanical, functional, or patient-reported outcome measures in adult and pediatric athletes with ACLR.

DATA SOURCES

Articles were selected from searches in 5 electronic databases (PubMed, EbscoHost [MEDLINE, SportDiscus, CINAHL Plus], PROQuest, Cochrane, and Embase).

STUDY SELECTION

Studies were included if they evaluated a post-ACL-RP that implemented strength, balance, plyometric, change of direction running, and/or agility running and included self-reported physical function, quality of life, or pain outcomes.

STUDY DESIGN

Scoping review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) guidelines.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Data were extracted and synthesized to evaluate the reporting of acute program variables (APVs) and exercise descriptors (EDs); 17 studies were included in the final synthesis.

RESULTS

Studies reported between 0% and 67% of the APVs and EDs combined. Only 2 studies were considered to have adequate reporting of both APVs and EDs.

CONCLUSION

Inadequate reporting of APVs and EDs in past studies restricts the translation and implementation of existing research-based ACL-RPs to present-day clinical contexts.

Nurse-Assisted Rehabilitation Protocols Following Anterior Cruciate Ligament Reconstruction

Despite significant advancements in surgical instruments and operation skills, short- and long-term outcomes following anterior cruciate ligament reconstruction (ACLR) remain unsatisfactory, as many patients fail to return to their pre-injury level of sports. Inadequate ACL rehabilitation is the primary cause of poor outcomes. Nurses have become a crucial element in the rehabilitation process. Although there is no consensus regarding the optimal post-operative rehabilitation protocols, restoring muscle strength and neuromuscular control are consistently the primary goals. This literature review presents nurse-assisted rehabilitation protocols aiming at improving muscle strength and neuromuscular control. The review discusses postoperative rehabilitation, including home-based and supervised rehabilitation, open and closed kinetic chain exercises, eccentric and concentric training, blood flow restriction training, and plyometric training. Each training protocol has its benefits and drawbacks, and should be used cautiously in specific stages of rehabilitation. Neuromuscular training, such as neuromuscular electrical stimulation, neuromuscular control exercises, and vibration therapy, is considered crucial in rehabilitation.

Resistance wheel running improves contractile strength, but not metabolic capacity, in a murine model of volumetric muscle loss injury

The primary objective of this study was to determine if low- or high-resistance voluntary wheel running leads to functional improvements in muscle strength (i.e., isometric and isokinetic torque) and metabolic function (i.e., permeabilized fibre bundle mitochondrial respiration) after a volumetric muscle loss (VML) injury. C57BL/6J mice were randomized into one of four experimental groups at age 12 weeks: uninjured control, VML untreated (VML), low-resistance wheel running (VML-LR) and high-resistance wheel running (VML-HR). All mice, excluding the uninjured, were subject to a unilateral VML injury to the plantar flexor muscles and wheel running began 3 days post-VML. At 8 weeks post-VML, peak isometric torque was greater in uninjured compared to all VML-injured groups, but both VML-LR and VML-HR had greater (∼32%) peak isometric torque compared to VML. All VML-injured groups had less isokinetic torque compared to uninjured, and there was no statistical difference among VML, VML-LR and VML-HR. No differences in cumulative running distance were observed between VML-LR and VML-HR groups. Because adaptations in VML-HR peak isometric torque were attributed to greater gastrocnemius muscle mass, atrophy- and hypertrophy-related protein content and post-translational modifications were explored via immunoblot; however, results were inconclusive. Permeabilized fibre bundle mitochondrial oxygen consumption was 22% greater in uninjured compared to VML, but there was no statistical difference among VML, VML-LR and VML-HR. Furthermore, neither wheel running group demonstrated a change in the relative protein content of the mitochondrial biogenesis transcription factor, peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α). These results indicate that resistance wheel running alone only has modest benefits in the VML-injured muscle. NEW FINDINGS: What is the central question of the study? Does initiation of a resistance wheel running regimen following volumetric muscle loss (VML) improve the functional capacity of skeletal muscle? What is the main finding and its importance? Resistance wheel running led to greater muscle mass and strength in mice with a VML injury but did not result in a full recovery. Neither low- nor high-resistance wheel running was associated with a change in permeabilized muscle fibre respiration despite runners having greater whole-body treadmill endurance capacity, suggesting resilience to metabolic adaptations in VML-injured muscle. Resistance wheel running may be a suitable adjuvant rehabilitation strategy, but alone does not fully mitigate VML pathology.

Chronic Adaptations to Eccentric Cycling Training: A Systematic Review and Meta-Analysis

This study aimed to investigate the effects of eccentric cycling (ECCCYC) training on performance, physiological, and morphological parameters in comparison to concentric cycling (CONCYC) training. Searches were conducted using PubMed, Embase, and ScienceDirect. Studies comparing the effect of ECCCYC and CONCYC training regimens on performance, physiological, and/or morphological parameters were included. Bayesian multilevel meta-analysis models were used to estimate the population's mean difference between chronic responses from ECCCYC and CONCYC training protocols. Group levels and meta-regression were used to evaluate the specific effects of subjects and study characteristics. Fourteen studies were included in this review. The meta-analyses showed that ECCCYC training was more effective in increasing knee extensor strength, vastus lateralis fiber cross-sectional area, and six-minute walking distance compared to CONCYC. Moreover, ECCCYC was as effective as CONCYC in decreasing body fat percentage. CONCYC was more effective in increasing V˙O2max and peak power output attained during concentric incremental tests. However, group-level analyses revealed that ECCCYC was more effective than CONCYC in improving V˙O2max in patients with cardiopulmonary diseases. ECCCYC is a viable modality for exercise interventions aiming to improve parameters of muscle strength, hypertrophy, functional capacity, aerobic power, and body composition, with more advantages than CONCYC training in improving neuromuscular variables.

Aspetar clinical practice guideline on rehabilitation after anterior cruciate ligament reconstruction

This guideline was developed to inform clinical practice on rehabilitation after anterior cruciate ligament reconstruction (ACLR) and was performed in accordance with the Appraisal of Guidelines for REsearch & Evaluation II (AGREE II) instrument and used the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. A Guideline Development Group systematically searched and reviewed evidence using randomised clinical trials and systematic reviews to evaluate the effectiveness of rehabilitation interventions and guide clinicians and patients on the content of the optimal rehabilitation protocol after ACLR.The guideline targets patients during rehabilitation after ACLR and investigates the effectiveness of the available interventions to the physiotherapist, alone or in combination (eg, exercise, modalities, objective progression criteria). Exercise interventions should be considered the mainstay of ACLR rehabilitation. However, there is little evidence on the dose-response relationship between volume and/or intensity of exercise and outcomes. Physical therapy modalities can be helpful as an adjunct in the early phase of rehabilitation when pain, swelling and limitations in range of motion are present. Adding modalities in the early phase may allow earlier pain-free commencement of exercise rehabilitation. Return to running and return to training/activity are key milestones for rehabilitation after ACLR. However, there is no evidence on which progression or discharge criteria should be used.While there is a very low level of certainty for most components of rehabilitation, most of the recommendations provided in this guideline were agreed to by expert clinicians. This guideline also highlights several new elements of ACLR management not reported previously.

A Short-Term Eccentric HIIT Induced Greater Reduction in Cardio-Metabolic Risk Markers in Comparison With Concentric HIIT in Sedentary Overweight Men

Background: Steady-state eccentric exercise training improves cardiometabolic risk (CMR) despite lesser cardiovascular demands compared with load-matched concentric training. Whether a high-intensity interval eccentric training is also effective reducing CMR is unknown. Aim: To compare the effects of a short-term high-intensity interval eccentric training (ECC-HIIT) with high-intensity interval concentric training (CONC-HIIT) on CMR in sedentary overweight men. Methods: Twenty men (age: 27.9 ± 5.3y, body massindex: 29.1 ± 3.1 kg·m-2) were randomly assigned to ECC-HIIT (n = 10) or CONC-HIIT (n = 10) delivered as six sessions, including 4 x 5:2 min work-to-rest ratio, at 80% peak concentric power output. Heart rate (HR), rate of perceived exertion (RPE) and muscle soreness weremonitored during training sessions. Training effects on lipid profile, insulin sensitivity (HOMA-IR), body composition, thigh circumference, isometric knee extensors maximal strength, resting systolic and diastolic blood pressure (SBP and DBP) were determined. Results: Average training HR and RPE were -29%and -50%lower in ECC-HIIT in comparison with CONC-HIIT. Muscle soreness was initially greater after ECC-HIIT compared with CONC-HIIT. Significant changes in total and low-density lipoprotein cholesterol (-7.0 ± 8.7%; p = .02 and -6.3 ± 14.4%; p = .03), SBP (-9.8 ± 7.8%; p = .002), and maximal thigh circumference (+2.5 ± 3.1%; p = .02) were observed following ECC-HIIT. No changes in any CMR marker were observed after CONC-HIIT. Moderate-to-large training effect sizes were obtained in thigh circumference, SBP, total cholesterol and low-density lipoprotein cholesterol in response to ECC-HIIT. Conclusion: A two-week ECC-HIIT was well-tolerated and induced rapid onset improvements in cholesterol and blood pressure compared to conventional CONC-HIIT in sedentary overweight men.

Unilateral Versus Bilateral Resistance Exercise in Postoperative Rehabilitation After ACL Reconstruction With Bone-Patellar Tendon-Bone Graft: A Randomized Controlled Trial

Background

Lower limb muscle strength symmetry has been suggested as an essential criterion for the safe return to sports after anterior cruciate ligament (ACL) reconstruction. Limited evidence is available regarding the most effective intervention to achieve symmetry after reconstruction with contralateral bone-patellar tendon-bone (BPTB) graft.

Purpose

To verify whether unilateral isotonic resistance exercise is more effective than bilateral exercise for obtaining postoperative functional and muscular strength symmetry between the donor limb and reconstructed limb for patients who received BPTB graft.

Study Design

Randomized controlled trial; Level of evidence, 1.

Methods

A total of 88 patients were randomly divided into a control group (n = 44) and an intervention group (n = 44). All participants performed an 8-week exercise program starting at the beginning of the fourth postoperative month and were evaluated before and after the program. The control group performed bilateral exercises, and the intervention group performed unilateral exercises for the donor limb only (the limb with the greatest disability). The primary outcome was muscle strength (peak torque and hamstrings to quadriceps [H:Q] ratio), and the secondary outcomes were range of motion (ROM; goniometry), KT-1000 arthrometer side-to-side difference in anteroposterior knee laxity, and objective (single-leg hop test) and subjective (Lysholm score) functionality.

Results

Both groups improved significantly from before to after the exercise program. The improvements were significantly greater in the intervention group regarding peak torque, H:Q ratio, flexion ROM, single-leg hop test, and Lysholm score in the donor limb (P < .001 for all), and the improvements were significantly greater in the control group regarding peak torque and single-leg hop test in the reconstructed limb (P < .001 for both). Comparison between the groups showed significantly increased symmetry regarding peak torque, H:Q ratio, and single-leg hop test in the intervention group compared with the control group (P < .001), with large effect sizes (>0.80) except for the H:Q ratio.

Conclusion

Although postoperative, bilateral, isotonic resistance exercise provided better strength gains to the reconstructed limb, unilateral exercise was more effective in obtaining functional and muscle strength between-limb symmetry in patients who underwent ACL reconstruction with contralateral BPTB graft.

Registration

Brazilian Registry of Clinical Trials (number RBR-22rnjh).

Arthrogenic Muscle Inhibition Following Anterior Cruciate Ligament Injury

Arthrogenic muscle inhibition (AMI) is a common impairment in individuals who sustain an anterior cruciate ligament (ACL) injury. The AMI causes decreased muscle activation, which impairs muscle strength, leading to aberrant movement biomechanics. The AMI is often resistant to traditional rehabilitation techniques, which leads to persistent neuromuscular deficits following ACL reconstruction. To better treat AMI following ACL injury and ACL reconstruction, it is important to understand the specific neural pathways involved in AMI pathogenesis, as well as the changes in muscle function that may impact movement biomechanics and long-term structural alterations to joint tissue. Overall, AMI is a critical factor that limits optimal rehabilitation outcomes following ACL injury and ACL reconstruction. This review discusses the current understanding of the: (1) neural pathways involved in the AMI pathogenesis following ACL injury; (2) consequence of AMI on muscle function, joint biomechanics, and patient function; and (3) development of posttraumatic osteoarthritis. Finally, the authors review the evidence for interventions specifically used to target AMI following ACL injury.

Contemporary Principles for Postoperative Rehabilitation and Return to Sport for Athletes Undergoing Anterior Cruciate Ligament Reconstruction

Despite advancements in our understanding of anterior cruciate ligament (ACL) injury prevention and nonsurgical management, ACL reconstruction continues to occur at an alarming rate. Among athletic patients, individuals participating in basketball, soccer, and football have the highest incidence of ACL injury, often requiring surgical intervention. To ensure the optimal treatment strategy for return to sport and prevention of secondary graft re-tear, it is important to tailor to the specific demands of the injured athlete and apply evidence-based best practices and rehabilitation principles. The purpose of this review is to provide readers with a brief background regarding ACL injuries, a focused review of clinical outcome studies after ACL reconstruction, and an updated framework with expert-guided recommendations for postoperative rehabilitation and return to sporting activity. Currently, there is no gold standard for rehabilitation after ACL reconstruction, highlighting the need for robust studies evaluating the best modalities for athlete rehabilitation, as well as determining the efficacy of new tools for improving therapy including blood flow restriction therapy and neuromuscular electrical stimulation. Based on clinical experience, a renewed focus on objective, criteria-based milestones may maximize the ability of return to preinjury levels of athletic function.

Use of rating of perceived exertion during anterior cruciate ligament reconstruction and knee osteoarthritis rehabilitation: a scoping review protocol

INTRODUCTION

Anterior cruciate ligament (ACL) tear and knee osteoarthritis (KOA) are the most prevalent musculoskeletal disorders of the knee. Rehabilitation with progressive resistance training is recommended for both disorders. Rating of perceived exertion (RPE) is widely used to prescribe, monitor, and control exercise load. However, the lack of detailed methodological description and variability in the use of RPE may hinder its validity. This scoping review summarises methodological aspects of the use of RPE in resistance exercises during ACL reconstruction and KOA rehabilitation. We also aim to identify possible methodological issues related to the use of RPE and provide recommendations for future studies.

METHODS AND ANALYSIS

This scoping review protocol was developed following the Joanna Briggs Institute and Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement extension for Scoping Reviews. The search will be conducted in Medline/PubMed, Embase, CINAHL, PEDro, Central and SPORTDiscus databases. The terms "anterior cruciate ligament rehabilitation", "knee osteoarthritis" and "resistance exercise" and their synonymous will be used isolated and combined (boolean operators AND/OR/NOT). Two reviewers will independently conduct title and abstract screening and evaluate full texts of potentially eligible articles. Data related to study design, sample, intervention characteristics and RPE outcomes will be extracted, summarised and qualitatively analysed.

ETHICS AND DISSEMINATION

The proposed scoping review does not require ethical approval since it will synthesise information from publicly available studies. Regarding dissemination activities, results will be submitted for publication in a scientific journal and presented at conferences in the field.

Arthrogenic Muscle Inhibition: Best Evidence, Mechanisms, and Theory for Treating the Unseen in Clinical Rehabilitation

CONTEXT

Arthrogenic muscle inhibition (AMI) impedes the recovery of muscle function following joint injury, and in a broader sense, acts as a limiting factor in rehabilitation if left untreated. Despite a call to treat the underlying pathophysiology of muscle dysfunction more than three decades ago, the continued widespread observations of post-traumatic muscular impairments are concerning, and suggest that interventions for AMI are not being successfully integrated into clinical practice.

OBJECTIVES

To highlight the clinical relevance of AMI, provide updated evidence for the use of clinically accessible therapeutic adjuncts to treat AMI, and discuss the known or theoretical mechanisms for these interventions.

EVIDENCE ACQUISITION

PubMed and Web of Science electronic databases were searched for articles that investigated the effectiveness or efficacy of interventions to treat outcomes relevant to AMI.

EVIDENCE SYNTHESIS

122 articles that investigated an intervention used to treat AMI among individuals with pathology or simulated pathology were retrieved from 1986 to 2021. Additional articles among uninjured individuals were considered when discussing mechanisms of effect.

CONCLUSION

AMI contributes to the characteristic muscular impairments observed in patients recovering from joint injuries. If left unresolved, AMI impedes short-term recovery and threatens patients' long-term joint health and well-being. Growing evidence supports the use of neuromodulatory strategies to facilitate muscle recovery over the course of rehabilitation. Interventions should be individualized to meet the needs of the patient through shared clinician-patient decision-making. At a minimum, we propose to keep the treatment approach simple by attempting to resolve inflammation, pain, and effusion early following injury.

Trunk and lower extremity long-axis rotation exercise improves forward single leg jump landing neuromuscular control

BACKGROUND

Anterior cruciate ligament (ACL) injuries often involve sudden single leg loading with directional changes. Trunk and lower extremity (LE) load transfer and muscle power are directly coupled during these movements. The effect of trunk and LE long-axis rotation training on forward single leg drop jump landing and stabilization (FSLDJLS) was studied.

METHODS

Using block randomization (gender), 36 (18 men, 18 women) subjects were assigned to experimental (nine, 20 min exercise sessions) and control groups with equal subject number. Ground reaction force (1000 Hz), kinematic (60 Hz) and LE EMG (1000 Hz) data were synchronously collected. Statistical analysis compared pre- and post-test neuromuscular control mean change differences (MCD), and hip flexion-LE peak EMG % maximum volitional isometric contraction (%MVIC) (expressed as decimal equivalents), mean change difference (MCD) relationships.

RESULTS

The experimental group had greater landing knee flexion (3.5 ± 3.6° vs. -0.4 ± 3.3°, p = .002) MCD, greater dynamic LE stiffness after landing (0.09 ± 0.14 vs. -0.11 ± 0.14, p = .001) MCD, and increased gluteus maximus (GMAX) (0.20 ± 0.39%MVIC vs. -0.23 ± 0.46%MVIC, p = .006) and gluteus medius (GMED) EMG amplitude (0.22 ± 0.31 vs. -0.07 ± 0.36%MVIC, p = .018) MCD. This group also had decreased GMAX (-166.5 ± 403.6 ms vs. 89.3 ± 196 ms, p = .025), GMED (-75.9 ± 126.8 ms vs. 131.2 ± 207.1 ms, p = .002) and vastus lateralis (-109.1 ± 365 ms vs. 205.5 vs. 510 ms, p = .04) activation duration MCD. More experimental group subjects had increased landing knee flexion MCD (15/18 vs. 8/18, p = .015), increased dynamic LE stiffness MCD (15/18 vs. 2/18, p < .0001) and increased GMAX (15/18 vs. 7/18, p = .006) and GMED (17/18 vs. 10/18, p = .007) EMG amplitude MCD, and reduced GMAX (12/18 vs. 6/18, p = .046), GMED (11/18 vs. 5/18, p = .044), rectus femoris (12/18 vs. 6/18, p = .046), and vastus lateralis (13/18 vs. 7/18, p = .044) EMG activation duration MCD. Only the experimental group displayed significant relationships between landing and peak hip flexion and peak LE EMG amplitude MCD.

CONCLUSION

Increased dynamic LE stiffness, increased hip muscle EMG amplitude and decreased hip and knee muscle activation duration MCD in the experimental group suggests improved LE neuromuscular control.

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.

Anterior Cruciate Ligament Reconstruction with Quadriceps Tendon-Patellar Bone Autograft and Dual Tibial Fixation

Anterior cruciate ligament ruptures are a relatively common injury in the athletic population, and surgical reconstruction is often indicated to restore knee stability. While hamstring tendon and patellar bone-tendon-bone autografts are a well-established graft choice in this population, there has been a growing body of literature supporting the benefits of quadriceps tendon autograft. Our technique illustrates a full-thickness quadriceps tendon-patellar bone autograft with dual tibial fixation using an interference screw and backup suspensory anchor fixation.

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).

Effect of Nordic Hamstring Exercise Training on Knee Flexors Eccentric Strength and Fascicle Length: A Systematic Review and Meta-Analysis

CONTEXT

Nordic hamstring exercise (NHE) has been widely employed to prevent hamstring strain injuries. However, it is still not clear which adaptations are responsible for the NHE preventive effects.

OBJECTIVES

The aim of this study was to investigate the effects of NHE on knee flexors eccentric strength and fascicle length.

EVIDENCE ACQUISITION

The search strategy included MEDLINE, PEDro, and Cochrane CENTRAL from inception to April 2020. Randomized clinical trials that have analyzed the effects of NHE training on hamstring eccentric strength and/or fascicle length were included.

EVIDENCE SYNTHESIS

From the 1932 studies identified, 12 were included in the systematic review, and 9 studies presented suitable data for the meta-analysis. All studies demonstrated strength increments in response to NHE training (10%-15% and 16%-26% in tests performed on the isokinetic dynamometer and on the NHE device, respectively), as well as significant enhancement of biceps femoris long head fascicle length (12%-22%). Meta-analysis showed NHE training was effective to increase knee flexors eccentric strength assessed with both isokinetic tests (0.68; 95% confidence interval, 0.29 to 1.06) and NHE tests (1.11; 95% confidence interval, 0.62 to 1.61). NHE training was also effective to increase fascicle length (0.97; 95% confidence interval, 0.46 to 1.48).

CONCLUSIONS

NHE training has the potential of increasing both knee flexors eccentric strength and biceps femoris long head fascicle length.

Michigan Initiative for Anterior Cruciate Ligament Rehabilitation (MiACLR): A Protocol for a Randomized Clinical Trial

OBJECTIVE

Restoring quadriceps muscle strength following anterior cruciate ligament reconstruction (ACLR) may prevent the posttraumatic osteoarthritis that affects over 50% of knees with ACLR. However, a fundamental gap exists in our understanding of how to maximize muscle strength through rehabilitation. Neurological deficits and muscle atrophy are 2 of the leading mechanisms of muscle weakness after ACLR. High-intensity neuromuscular electrical stimulation (NMES) and eccentric exercise (ECC) have been shown to independently target these mechanisms. If delivered in succession, NMES and then ECC may be able to significantly improve strength recovery. The objectives of this study were to evaluate the ability of NMES combined with ECC to restore quadriceps strength and biomechanical symmetry and maintain cartilage health at 9 and 18 months after ACLR.

METHODS

This study is a randomized, double-blind, placebo-controlled, single-center clinical trial conducted at the University of Michigan. A total of 112 participants between the ages of 14 and 45 years and with an anterior cruciate ligament rupture will be included. Participants will be randomly assigned 1:1 to NMES combined with ECC or NMES placebo combined with ECC placebo. NMES or NMES placebo will be delivered 2 times per week for 8 weeks beginning 10 to 14 days postoperatively and will be directly followed by 8 weeks of ECC or ECC placebo delivered 2 times per week. The co-primary endpoints are change from baseline to 9 months and change from baseline to 18 months after ACLR in isokinetic quadriceps strength symmetry. Secondary outcome measures include isometric quadriceps strength, quadriceps activation, quadriceps muscle morphology (cross-sectional area), knee biomechanics (sagittal plane knee angles and moments), indexes of patient-reported function, and cartilage health (T1ρ and T2 relaxation time mapping on magnetic resonance imaging).

IMPACT

The findings from this study might identify an intervention capable of targeting the lingering quadriceps weakness after ACLR and in turn prevent deterioration in cartilage health after ACLR, thereby potentially improving function in this patient population.

Blood Flow Restriction Training Applied With High-Intensity Exercise Does Not Improve Quadriceps Muscle Function After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

BACKGROUND

A major goal of rehabilitation after anterior cruciate ligament reconstruction (ACLR) is restoring quadriceps muscle strength. Unfortunately, current rehabilitation paradigms fall short of this goal, such that substantial quadriceps muscle strength deficits can limit return to play and increase the risk of recurrent injuries. Blood flow restriction training (BFRT) involves the obstruction of venous return to working muscles during exercise and may lead to better recovery of quadriceps muscle strength after ACLR.

PURPOSE

To examine the efficacy of BFRT with high-intensity exercise on the recovery of quadriceps muscle function in patients undergoing ACLR.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 34 patients (19 female, 15 male; mean age, 16.5 ± 2.7 years; mean height, 169.0 ± 19.7 cm; mean weight, 73.2 ± 17.7 kg) scheduled to undergo ACLR were randomly assigned to 1 of 4 groups: concentric (n = 8), eccentric (n = 8), concentric with BFRT (n = 9), and eccentric with BFRT (n = 9). The exercise component of the intervention consisted of patients performing a single-leg isokinetic leg press, at an intensity of 70% of the patients' 1-repetition maximum during either the concentric or eccentric action, for 4 sets of 10 repetitions 2 times per week for 8 weeks beginning at 10 weeks postoperatively. Patients randomized to the BFRT groups performed the leg-press exercise with a cuff applied to the thigh, set to a limb occlusion pressure of 80%. Isometric and isokinetic (60 deg/s) quadriceps peak torque, quadriceps muscle activation, and rectus femoris muscle volume were assessed before ACLR, after BFRT, and at the time that patients returned to activity and were converted to the change in values from baseline for analysis. Also, 1-way analyses of covariance were used to compare the change in values for each dependent variable between groups after BFRT and at return to activity (P ≤ .05).

RESULTS

No significant differences were found between groups for any outcome measures at either time point (P > .05).

CONCLUSION

An 8-week BFRT plus high-intensity exercise intervention did not significantly improve quadriceps muscle strength, activation, or volume. On the basis of our findings, the use of BFRT in conjunction with high-intensity resistance exercise in patients undergoing ACLR to improve quadriceps muscle function may not be warranted.

REGISTRATION

NCT03141801 ( ClinicalTrials.gov identifier).

Quadriceps Muscle Size Following ACL Injury and Reconstruction: A Systematic Review

Image-based assessments of quadriceps muscle size facilitate examination of structural changes after anterior cruciate ligament (ACL) injury and reconstruction (ACLR). Understanding the effects of ACLR on muscle size measures may aid in clarifying the contribution of quadriceps atrophy toward quadriceps strength. The purpose of this study was to systematically review the literature examining the effects of ACLR on quadriceps muscle volume and cross-sectional area (CSA). An online database search was conducted using Web of Science, SportDISCUS, PubMed (Medline), CINHAL (EBSCO), and Cochrane Library limited to articles published after January 1, 1980. Means and standard deviations were extracted for the ACLR limb and the contralateral limb, and sample characteristics from relevant articles. Magnitude of between limb differences were assessed using pooled effect sizes (Hedge's g) and 95% confidence intervals. Eleven articles (five CSA, six muscle volume) were included in this systematic review. Included studies reported negative effective sizes, indicating that the ACLR limb was smaller in CSA or muscle volume compared with the contralateral limb; however, 36% of the included articles reported meaningful difference between the limbs. Quadriceps atrophy may occur following ACL injury and persist after rehabilitation, however, the magnitude of these reductions may not be clinically meaningful and may only partially explain the persistent quadriceps weakness that is ubiquitous among this patient population. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:598-608, 2020.

Eccentric Overload Flywheel Training in Older Adults

Age-related reductions in muscle strength and muscle power can have significant adverse effects on functional performance in older adults. Exercise training has been shown to be a potent stimulus for improvements in strength and power. However, investigation into how to best optimize training-related adaptations, as well as the accessibility of training methods, is needed. Traditional (TR) methods using gravity-dependent free-weights or weight machines can improve and maintain strength and power but are limited in their ability to provide constant muscle tension and high levels of muscle activation throughout the lowering (eccentric) phase of lifting. Eccentric overload (EO) training may overcome these limitations and has been shown to result in potent adaptations in both young and older adults. Methods of producing EO are significantly limited from a practical perspective. The addition of whole-body flywheel training equipment provides a practical method of producing EO and may be appropriate for older adults wanting to optimize training outcomes. Our review provides limited evidence of the use of eccentric overload flywheel training as a novel training method in seniors. Through the review of literature, EO training overcame some of the limitations set forth by traditional resistance training and demonstrated to have key benefits when combating age-related changes affecting muscle strength and muscle power. It can be concluded that EO training is an important addition to the training arsenal for older adults. Flywheel training provides a practical method of achieving EO, increasing strength and power, combating age-related adaptations, and overall improving quality of life in older adults.

Isokinetic knee strength and proprioception before and after anterior cruciate ligament reconstruction: A comparison between home-based and supervised rehabilitation

BACKGROUND

Rehabilitation after anterior cruciate ligament (ACL) reconstruction focuses on restoring knee deficiencies and function. However, the extent of the clinician's direct supervision that is required to recover knee function is unknown.

OBJECTIVE

To investigate differences in isokinetic knee strength improvement, endurance, and proprioception between home-based (HBR) and supervised rehabilitation (SR).

METHODS

Thirty participants were randomly allocated to each group after reconstruction. Isokinetic knee strength and proprioception were measured using the Biodex multi-joint and stability systems, respectively, before and after intervention.

RESULTS

The SR group showed a significant improvement from baseline, but not the HBR group (SR group, from 1.94 ± 1.44 to 1.02 ± 0.92, p< 0.05; HBR group, from 1.69 ± 0.88 to 1.61 ± 0.90, p> 0.05). There was a significant effect of exercise type on proprioception scores after controlling for pretest values (p< 0.05). No significant difference in isokinetic knee strength was observed between the groups.

CONCLUSIONS

HBR recovered knee strength as effectively as the SR, but SR was more effective than HBR for the recovery of proprioception and functional knee movement. This result indicates that guidance from health professionals play an important role in enhancing proprioception for patients following ACL reconstruction.

Implementing Eccentric Resistance Training-Part 2: Practical Recommendations

The purpose of this review is to provide strength and conditioning practitioners with recommendations on how best to implement tempo eccentric training (TEMPO), flywheel inertial training (FIT), accentuated eccentric loading (AEL), and plyometric training (PT) into resistance training programs that seek to improve an athlete's hypertrophy, strength, and power output. Based on the existing literature, TEMPO may be best implemented with weaker athletes to benefit positional strength and hypertrophy due to the time under tension. FIT may provide an effective hypertrophy, strength, and power stimulus for untrained and weaker individuals; however, stronger individuals may not receive the same eccentric (ECC) overload stimulus. Although AEL may be implemented throughout the training year to benefit hypertrophy, strength, and power output, this strategy is better suited for stronger individuals. When weaker and stronger individuals are exposed to PT, they are exposed to an ECC overload stimulus as a result of increases in the ECC force and ECC rate of force development. In conclusion, when choosing to utilize ECC training methods, the practitioner must integrate these methods into a holistic training program that is designed to improve the athlete's performance capacity.

Isokinetic eccentric training is more effective than constant load eccentric training for quadriceps rehabilitation following anterior cruciate ligament reconstruction: a randomized controlled trial

OBJECTIVE

To compare the effects of conventional (constant load) eccentric training and isokinetic eccentric training on quadriceps muscle mass, strength and functional performance in recreational athletes following anterior cruciate ligament (ACL) reconstruction.

METHODS

Thirty recreational male athletes (25 years old) undergoing ACL reconstruction received a standard rehabilitation program. Volunteers were randomized to conventional group (CG; n = 15) or isokinetic group (IG; n = 15) to be engaged in a 6-week (2 sessions/week) quadriceps eccentric training program at the extensor chair or at the isokinetic dynamometer, respectively. Assessments of quadriceps muscle mass (through magnetic resonance imaging), strength (through isokinetic dynamometry) and self-aware functionality (through questionnaire) were performed before and after the training programs. Single leg hop test performance was assessed only at post-training evaluation.

RESULTS

IG had significantly higher improvements than CG (p < 0.05) for all muscle mass outcomes (+17-23% vs. +5-9%), as well as for isometric (+34% vs. +20%) and eccentric (+85% vs. +23%) peak torques. There was no between-group difference (p > 0.05) for concentric peak torque, Lysholm score, and single leg hop test.

CONCLUSION

Isokinetic eccentric training promotes greater responses than conventional eccentric training on quadriceps muscle mass and strength of recreational athletes following ACL reconstruction.

Eccentric Muscle Contractions: Risks and Benefits

Eccentric contractions, characterized by the lengthening of the muscle-tendon complex, present several unique features compared with other types of contractions, which may lead to unique adaptations. Due to its specific physiological and mechanical properties, there is an increasing interest in employing eccentric muscle work for rehabilitation and clinical purposes. However, unaccustomed eccentric exercise is known to cause muscle damage and delayed pain, commonly defined as “Delayed-Onset Muscular Soreness” (DOMS). To date, the most useful preventive strategy to avoid these adverse effects consists of repeating sessions involving submaximal eccentric contractions whose intensity is progressively increased over the training. Despite an increased number of investigations focusing on the eccentric contraction, a significant gap still remains in our understanding of the cellular and molecular mechanisms underlying the initial damage response and subsequent adaptations to eccentric exercise. Yet, unraveling the molecular basis of exercise-related muscle damage and soreness might help uncover the mechanistic basis of pathological conditions as myalgia or neuromuscular diseases. In addition, a better insight into the mechanisms governing eccentric training adaptations should provide invaluable information for designing therapeutic interventions and identifying potential therapeutic targets.

Muscle hypotrophy, not inhibition, is responsible for quadriceps weakness during rehabilitation after anterior cruciate ligament reconstruction

PURPOSE

Quadriceps weakness is common after anterior cruciate ligament reconstruction (ACLR). Limited neuromuscular activation may have a role in the weakness. The purpose of this study was to use peripheral magnetic stimulation to measure changes in quadriceps inhibition in patients during rehabilitation from ACLR.

METHODS

Ten patients (7M/3F; age 35 ± 8 years; BMI 26.0 ± 4.8 kg/m²) who had ACLR with patellar tendon autograft were recruited. At 3 and 6 months postoperatively, patients' knee extension peak torque was measured during maximum voluntary isometric contraction (MVIC), magnetic stimulation-evoked contraction, and MVIC augmented with superimposed burst magnetic stimulation to the femoral nerve. All tests were done bilaterally at 30° and 65° of knee flexion on a dynamometer. Central activation ratio was calculated by dividing the peak torque before stimulation by peak torque after stimulation.

RESULTS

Patients had marked deficits in MVIC, with improvement from 3 to 6 months that was more apparent at 65° versus 30° (P < 0.05). There was significant deficit in stimulation-evoked torque on the involved side that diminished over time, and this change occurred differently between the two angles (P < 0.05). Central activation ratio was lower on the involved side versus the noninvolved side and this effect was more prominent at 3 versus 6 months: combining the angles, mean central activation ratio on the involved and noninvolved sides, respectively, was 91.4 ± 7.6% and 97.5 ± 5.3% at 3 months, and 93.0 ± 7.8% and 95.8 ± 6.8% at 6 months.

CONCLUSIONS

At 3 and 6 months after ACLR, there were significant deficits in quadriceps strength and activation. Quadriceps activation levels were high (> 90%) for both sides at both time points. The substantial strength deficits at this postoperative period may be largely due to muscle atrophy with limited contribution from central inhibition. Rehabilitation interventions to normalize quadriceps strength should emphasize hypertrophic stimuli as opposed to neuromuscular activation strategies.

LEVEL OF EVIDENCE

II, prospective cohort study.

MRI-Based Assessment of Lower-Extremity Muscle Volumes in Patients Before and After ACL Reconstruction

Context:Study of muscle volumes in patients after anterior cruciate ligament (ACL) injury and reconstruction (ACL-R) is largely limited to cross-sectional assessment of the thigh musculature, which may inadequately describe posttraumatic and postsurgical muscle function. No studies have prospectively examined the influence of ACL injury and reconstruction on lower-extremity muscle volumes.Objective:Assess magnetic resonance imaging-derived lower-extremity muscle volumes, and quantify quadriceps strength and activation in patients following ACL injury and reconstruction.Design:Prospective case series.Setting:Research laboratory and magnetic resonance imaging facility.Patients (or Other Participants):Four patients (2 men and 2 women; age = 27.4 (7.4) y, height = 169.2 (8.1) cm, and mass = 74.3 (18.5) kg) scheduled for ACL-R.Intervention(s):Thirty-five muscle volumes were obtained from a bilateral lower-extremity magnetic resonance imaging before and after ACL-R.Main Outcome Measures:Muscle volumes expressed relative to (1) a normative database presurgery and postsurgery, (2) limb symmetry presurgery and postsurgery, and (3) percentage change presurgery to postsurgery. Quadriceps function was quantified by normalized knee extension maximal voluntary isometric contraction torque and central activation ratio.Results:Involved vastus lateralis and tibialis anterior were consistently smaller than healthy individuals (z < −1 SD) presurgery and postsurgery in all patients. Involved rectus femoris and vastus lateralis were more than 15% smaller than the contralateral limb presurgery, whereas the involved rectus femoris, gracilis, vastus medialis, vastus intermedius, and vastus lateralis muscle volumes exceeded 20% asymmetry postoperatively. Involved gracilis and semitendinosus atrophied more than 30% from presurgery to postsurgery. Involved maximal voluntary isometric contraction torque and central activation ratio increased by 12.7% and 12.5%, respectively, yet strength remained 33.2% asymmetric postsurgery.Conclusions:Adaptations in lower-extremity muscle volumes are present following ACL injury and reconstruction. Anterior thigh and shank muscles were smaller than healthy individuals, and large asymmetries in quadriceps volumes were observed presurgery and postsurgery. Selective atrophy of the semitendinosus and gracilis occurred following surgery. Volumetric deficits of the quadriceps musculature may exist despite improvements in muscle strength and activation.

Contribution of Neuromuscular Factors to Quadriceps Asymmetry After Anterior Cruciate Ligament Reconstruction

CONTEXT

  To quantify quadriceps weakness after anterior cruciate ligament reconstruction (ACLR), researchers have often analyzed only peak torque. However, analyzing other characteristics of the waveform, such as the rate of torque development (RTD), time to peak torque (TTP), and central activation ratio (CAR), can lend insight into the underlying neuromuscular factors that regulate torque development.

OBJECTIVE

  To determine if interlimb neuromuscular asymmetry was present in patients with ACLR at the time of clearance to return to activity.

DESIGN

  Cross-sectional study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 10 individuals serving as controls (6 men, 4 women; age = 23.50 ± 3.44 years, height = 1.73 ± 0.09 m, mass = 71.79 ± 9.91 kg) and 67 patients with ACLR (43 men, 24 women; age = 21.34 ± 5.73 years, height = 1.74 ± 0.11 m, mass = 77.85 ± 16.03 kg, time postsurgery = 7.52 ± 1.36 months) participated.

MAIN OUTCOME MEASURE(S)

  Isokinetic (60°/s) and isometric quadriceps strength were measured. Peak torque, TTP, and RTD were calculated across isometric and isokinetic trials, and CAR was calculated from the isometric trials via the superimposed burst. Repeated-measures analyses of variance were used to compare limbs in the ACLR and control groups.

RESULTS

  No between-limbs differences were detected in the control group ( P > .05). In the ACLR group, the involved limb demonstrated a longer TTP for isokinetic strength ( P = .04; Cohen d effect size [ES] = 0.18; 95% confidence interval [CI] = -0.16, 0.52), lower RTD for isometric ( P < .001; Cohen d ES = 0.73; 95% CI = 0.38, 1.08) and isokinetic ( P < .001; Cohen d ES = 0.84; 95% CI = 0.49, 1.19) strength, lower CAR ( P < .001; Cohen d ES = 0.37; 95% CI = 0.03, 0.71), and lower peak torque for isometric ( P < .001; Cohen d ES = 1.28; 95% CI = 0.91, 1.65) and isokinetic ( P < .001; Cohen d ES = 1.15; 95% CI = 0.78, 1.52) strength.

CONCLUSIONS

  Interlimb asymmetries at return to activity after ACLR appeared to be regulated by several underlying neuromuscular factors. We theorize that interlimb asymmetries in isometric and isokinetic quadriceps strength were associated with changes in muscle architecture. Reduced CAR, TTP, and RTD were also present, indicating a loss of motor-unit recruitment or decrease in firing rate.

Pharmacological inhibition of myostatin protects against skeletal muscle atrophy and weakness after anterior cruciate ligament tear

Anterior cruciate ligament (ACL) tears are among the most frequent knee injuries in sports medicine, with tear rates in the US up to 250,000 per year. Many patients who suffer from ACL tears have persistent atrophy and weakness even after considerable rehabilitation. Myostatin is a cytokine that directly induces muscle atrophy, and previous studies rodent models and patients have demonstrated an upregulation of myostatin after ACL tear. Using a preclinical rat model, our objective was to determine if the use of a bioneutralizing antibody against myostatin could prevent muscle atrophy and weakness after ACL tear. Rats underwent a surgically induced ACL tear and were treated with either a bioneutralizing antibody against myostatin (10B3, GlaxoSmithKline) or a sham antibody (E1-82.15, GlaxoSmithKline). Muscles were harvested at either 7 or 21 days after induction of a tear to measure changes in contractile function, fiber size, and genes involved in muscle atrophy and hypertrophy. These time points were selected to evaluate early and later changes in muscle structure and function. Compared to the sham antibody group, 7 days after ACL tear, myostatin inhibition reduced the expression of proteolytic genes and induced the expression of hypertrophy genes. These early changes in gene expression lead to a 22% increase in muscle fiber cross-sectional area and a 10% improvement in maximum isometric force production that were observed 21 days after ACL tear. Overall, myostatin inhibition lead to several favorable, although modest, changes in molecular biomarkers of muscle regeneration and reduced muscle atrophy and weakness following ACL tear. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2499-2505, 2017.

Back to the future! Revisiting the physiological cost of negative work as a team-based activity for exercise physiology students

We implemented a team-based activity in our exercise physiology teaching laboratory that was inspired from Abbott et al.'s classic 1952 Journal of Physiology paper titled "The physiological cost of negative work." Abbott et al. connected two bicycles via one chain. One person cycled forward (muscle shortening contractions, positive work) while the other resisted the reverse moving pedals (muscle lengthening contractions, negative work), and the cost of work was compared. This study was the first to link human whole body energetics with isolated muscle force-velocity characteristics. The laboratory activity for our students (n = 35) was designed to reenact Abbott et al.'s experiment, integrate previously learned techniques, and illustrate differences in physiological responses to muscle shortening and lengthening contractions. Students (11-12 students/laboratory section) were split into two teams (positive work vs. negative work). One student from each team volunteered to cycle against the other for ~10 min. The remaining students in each team were tasked with measuring: 1) O₂ consumption, 2) heart rate, 3) blood lactate, and 4) perceived exertion. Students discovered that O₂ consumption during negative work was about one-half that of positive work and all other physiological parameters were also substantially lower. Muscle lengthening contractions were discussed and applied to rehabilitation and sport training. The majority of students (>90%) agreed or strongly agreed that they stayed engaged during the activity and it improved their understanding of exercise physiology. All students recommended the activity be performed again. This activity was engaging, emphasized teamwork, yielded clear results, was well received, and preserved the history of classic physiological experiments.

Moderate Load Eccentric Exercise; A Distinct Novel Training Modality

Over the last 20 years a number of studies have been published using progressive eccentric exercise protocols on motorized ergometers or similar devices that allow for controlled application of eccentric loads. Exercise protocols ramp eccentric loads over an initial 3 weeks period in order to prevent muscle damage and delayed onset muscle soreness. Final training loads reach 400-500 W in rehabilitative settings and over 1200 W in elite athletes. Training is typically carried out three times per week for durations of 20-30 min. This type of training has been characterizes as moderate load eccentric exercise. It has also been denoted RENEW (Resistance Exercise via Negative Eccentric Work by LaStayo et al., 2014). It is distinct from plyometric exercises (i.e., drop jumps) that impose muscle loads of several thousand Watts on muscles and tendons. It is also distinct from eccentric overload training whereby loads in a conventional strength training setting are increased in the eccentric phase of the movement to match concentric loads. Moderate load eccentric exercise (or RENEW) has been shown to be similarly effective as conventional strength training in increasing muscle strength and muscle volume. However, as carried out at higher angular velocities of joint movement, it reduces joint loads. A hallmark of moderate load eccentric exercise is the fact that the energy requirements are typically 4-fold smaller than in concentric exercise of the same load. This makes moderate load eccentric exercise training the tool of choice in medical conditions with limitations in muscle energy supply. The use and effectiveness of moderate load eccentric exercise has been demonstrated mostly in small scale studies for cardiorespiratory conditions, sarcopenia of old age, cancer, diabetes type 2, and neurological conditions. It has also been used effectively in the prevention and rehabilitation of injuries of the locomotor system in particular the rehabilitation after anterior cruciate ligament surgery.

Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus

AIM

The Royal Dutch Society for Physical Therapy (KNGF) instructed a multidisciplinary group of Dutch anterior cruciate ligament (ACL) experts to develop an evidence statement for rehabilitation after ACL reconstruction.

DESIGN

Clinical practice guideline underpinned by systematic review and expert consensus.

DATA SOURCES

A multidisciplinary working group and steering group systematically reviewed the literature and wrote the guideline. MEDLINE and the Cochrane Library were searched for meta-analyses, systematic reviews, randomised controlled trials and prospective cohort studies published between January 1990 and June 2015.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Included literature must have addressed 1 of 9 predetermined clinical topics: (1) preoperative predictors for postoperative outcome, (2) effectiveness of physical therapy, (3) open and closed kinetic chain quadriceps exercises, (4) strength and neuromuscular training, (5) electrostimulation and electromyographic feedback, (6) cryotherapy, (7) measurements of functional performance, (8) return to play and (9) risk for reinjury.

SUMMARY

Ninety studies were included as the basis for the evidence statement. Rehabilitation after ACL injury should include a prehabilitation phase and 3 criterion-based postoperative phases: (1) impairment-based, (2) sport-specific training and (3) return to play. A battery of strength and hop tests, quality of movement and psychological tests should be used to guide progression from one rehabilitation stage to the next. Postoperative rehabilitation should continue for 9-12 months. To assess readiness to return to play and the risk for reinjury, a test battery, including strength tests, hop tests and measurement of movement quality, should be used.

Enhanced knee joint function due to accelerated rehabilitation exercise after anterior cruciate ligament reconstruction surgery in Korean male high school soccer players

This study was conducted on Korean male high school soccer players who underwent anterior cruciate ligament reconstruction (ACLR) to identify the effects of an accelerated rehabilitation exercise (ARE) program on knee joint isometric strength, thigh circumference, Lysholm score, and active balance agility. We assigned eight test participants each to a physical therapy group (PTG) and an accelerated rehabilitation exercise group (AREG), and compared differences between the groups. Both the PTG and AREG showed significant increases in 30° away and 60° toward isometric strength after treatment. In addition, significant differences were observed in these strength tests between the two groups. Both groups also showed significant increases in thigh circumference, Lysholm score, and active balance agility after treatment, but no significant differences were observed between the two groups. We conclude that the ARE treatment was more effective for improving isometric strength of the knee joint than that of physical therapy, and that an active rehabilitation exercise program after ACLR had positive effects on recovery performance of patients with an ACL injury and their return to the playing field.

Deficits in Quadriceps Strength and Patient-Oriented Outcomes at Return to Activity After ACL Reconstruction: A Review of the Current Literature

Context:

Side-to-side quadriceps strength deficits are linked to hazardous lower extremity mechanics and reduced function at a time when individuals are returned to activity after anterior cruciate ligament (ACL) reconstruction. As a result, generalized criteria have emerged in the literature, wherein researchers are recommending that patients be cleared for participation once side-to-side differences in strength are ≤10% of the noninjured limb. Similar recommendations exist for patient-oriented outcomes (ie, self-reported function and hop tests), where deficits of ≤10% are considered ideal at return to activity. It is unclear how many studies actually achieve these clinically recommended results.

Evidence Acquisition:

Articles that reported quadriceps strength deficits as compared to the contralateral limb were collected from peer-reviewed sources available on Medline and Web of Science databases (1990 through August 2014). Search terms included the following: anterior cruciate ligament OR ACL AND muscle weakness, anterior cruciate ligament OR ACL AND strength; return-to-activity AND strength; anterior cruciate ligament OR ACL AND quadriceps.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

Average side-to-side strength deficits at 6 months postreconstruction were 23% ± 8% (range, 3%-40%), while the average at 12 months postsurgery was found to be 14% ± 6% (range, 3%-28%). The average deficits in self-reported function at 6 months (mean, 14% ± 5%) and 12 months postsurgery (mean, 13% ± 6%) were also found to be >10%. Performance on hop tests was found to be less than optimal at 6 months postsurgery (mean, 11% ± 7%), but improved at 12 months postsurgery (mean, 1.3% ± 2%).

Conclusion:

This review provides an up-to-date account of the typical deficits in strength and patient-oriented outcomes that exist when formalized physical therapy concludes after ACL reconstruction. Based on the studies included, it seems pertinent that researchers and clinicians continue to investigate interventions capable of improving the recovery of quadriceps strength as well as patient-oriented outcomes as the majority of studies report levels that are well below clinical recommendations.

Combination of eccentric exercise and neuromuscular electrical stimulation to improve quadriceps function post-ACL reconstruction

BACKGROUND

Neuromuscular electrical stimulation (NMES) has been shown to reduce quadriceps activation failure (QAF), and eccentric exercise has been shown to lessen muscle atrophy post-ACL reconstruction. Given that these are two critical components of quadriceps strength, intervention combining these therapies may be effective at reinstituting quadriceps function post-reconstruction. Thus, the aim of this study was to evaluate the effectiveness of a combined NMES and eccentric exercise intervention to improve the recovery of quadriceps activation and strength post-reconstruction.

METHODS

Thirty-six individuals post-injury were placed into four treatment groups (N&E, NMES and eccentrics; E-only, eccentrics only; N-only, NMES-only; and STND, standard of care) and ten healthy controls participated. N&E and N-only received the NMES protocol 2× per week for the first 6 weeks post-reconstruction. N&E and E-only received the eccentric exercise protocol 2× per week beginning 6 weeks post-reconstruction. Quadriceps activation was assessed via the superimposed burst technique and quantified via the central activation ratio. Quadriceps strength was assessed via maximal voluntary isomeric contractions (Nm/kg). Data was gathered on three occasions: pre-operative, 12-weeks-post-surgery and at return-to-play.

RESULTS

No differences in pre-operative measures existed (P>0.05). E-only recovered quadriceps activation better than N-only or STND (P<0.05). N&E and E-only recovered strength better than N-only or the STND (P<0.05) and had strength values that were similar to healthy at return-to-play (P>0.05).

CONCLUSION

Eccentric exercise was capable of restoring levels of quadriceps activation and strength that were similar to those of healthy adults and better than NMES alone.

LEVEL OF EVIDENCE

Level 3, Parallel longitudinal study.

Serum cytokines and muscle strength after anterior cruciate ligament surgery are not modulated by high-doses of vitamins E (α- and γ-tocopherol's) and C

The purpose of this investigation was to identify if supplemental vitamin E (consisting of α- and γ-tocopherol's) and C modulate serum cytokine and muscle strength following an ACL injury and surgery. Subjects were randomly assigned to one of two groups: (1) placebo (n=14) or (2) vitamins E (α-[600m g RRR-α-tocopherol, αT] and γ-[600 mg of RRR-γT]) and C (1000 mg ascorbic acid, AA) (EC; n=15). Supplements were taken daily starting ∼2-wk prior to and concluding 16-wk after surgery. Fasting blood samples were obtained and single-leg peak isometric force measurements were performed at baseline (prior to supplementation), before surgery (∼120-min - blood draw only), and 8-wk, 12-wk, and 16-wk after surgery. αT, γT, AA, and cytokines were measured in each blood sample, and peak isometric force was measured on the injured and non-injured legs separately at each testing session. An exercise protocol consisting of repetitive knee and hip extension and flexion contractions to exhaustion was performed on the injured limb at 16-wk. Vitamin E and C supplementation significantly (all p<0.05) increased plasma αT (∼40%), γT (∼160%), and AA (∼50%) concentrations. Serum cytokine concentrations, peak isometric force, and time to exhaustion during the exercise protocol were not significantly different between groups. Based on these findings, we conclude that vitamin E and C supplementation increases their endogenous levels without minimizing muscular weakness or modulating serum cytokine concentrations after ACL surgery.

Clinical strategies for addressing muscle weakness following knee injury

Muscle strength is a determinate of physical function and increasing muscle strength is an important clinical goal for patients with knee injury. This article discusses the emerging evidence regarding a novel rehabilitation strategy that uses disinhibitory modalities to increase neuromuscular activation in conjunction with traditional muscle strengthening for the purpose of maximizing strength gains following acute knee injury or surgery and in patients with knee osteoarthritis. The use of disinhibitory modalities and specific types of neuromuscular training for clinically maximizing strength are discussed.

What can the first 2 months tell us about outcomes after anterior cruciate ligament reconstruction?

CONTEXT

Substantial research has been conducted on anterior cruciate ligament reconstruction (ACLR) to evaluate patient outcomes. However, little attention has been given to outcomes during the early phase of recovery and how early deficits affect both short- and long-term outcomes.

OBJECTIVE

To identify relationships between demographic (age, sex, and body mass index [BMI]) and intraoperative (isolated ACLR versus primary ACLR + secondary procedures), and postoperative (range-of-motion [ROM] and peak isometric knee-extension force [PIF]) variables during the first 2 months after ACLR using self-reported outcomes.

DESIGN

Cohort study.

SETTING

Outpatient orthopaedic hospital.

PATIENTS OR OTHER PARTICIPANTS

A total of 63 patients (38 men, 25 women; age = 33.0 ± 12.1 years; BMI = 26.3 ± 6.5 kg/m(2)) who underwent ACLR.

MAIN OUTCOME MEASURE(S)

Demographic, intraoperative, and postoperative variables were collected at 1 and 2 months after ACLR and were compared with International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form scores at 1, 2, and ≥12 months.

RESULTS

Significant relationships were identified between ≥12-month IKDC scores and the 1-month (Pearson correlation, r = 0.283, r(2) = 0.08; P = .025) and 2-month (r = 0.301, r(2) = 0.09; P = .017) IKDC scores. After controlling for other variables, we found that the PIF ratio measures at 1 and 2 months were positively associated with 1- and 2-month IKDC scores (P < .001) and BMI was negatively associated with both 1- and 2-month IKDC scores (P < .05). One-month IKDC scores were related to the 1-month difference in knee-flexion ROM (P = .04).

CONCLUSIONS

The IKDC scores during the first 2 months were positively correlated with patients' perceptions of function on long-term IKDC scores. It also appears that improvements in lower extremity strength and flexion ROM deficits were positively associated with short-term IKDC scores. Higher BMI was negatively associated with patients' perceptions of function on short-term IKDC scores.

Knee moment and shear force are correlated with femoral tunnel orientation after single-bundle anterior cruciate ligament reconstruction

BACKGROUND

Increasing evidence has shown that anatomic single-bundle anterior cruciate ligament reconstruction (ACLR) better restores normal knee kinematics and functionality than nonanatomic ACLR. Whether anatomic reconstruction results in better knee kinetics during daily activities has not been fully investigated.

PURPOSE

To assess the relationship between femoral tunnel angle and kinetic parameters of the knee joint during walking after single-bundle ACLR and to compare the radiographic and kinetic results of patients who underwent anatomic ACLR with those of patients who underwent nonanatomic ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-one patients who underwent unilateral ACLR were recruited, and 20 healthy subjects from a previous study were used as a control group. All surgical procedures were performed by a single surgeon, 11 using the transtibial (TT) technique and 10 using the anteromedial portal (AMP) technique. Femoral tunnel orientation was measured from posterior-to-anterior radiographs. Dynamic knee joint moments and shear forces during gait were evaluated using 3-dimensional motion analysis and inverse dynamics. Relationships between femoral tunnel angles and kinetic results were evaluated via linear regression. Results were compared between 2 ACLR groups and controls using 1-way analysis of variance.

RESULTS

Femoral tunnel angle had significant correlations with peak external knee flexion moment and posterior shear force during early stance. The TT group had a significantly smaller (more vertical) mean femoral tunnel angle (19.4° ± 4.1°) than the AMP group (36.4° ± 5.8°). Significant reductions were found in the normalized peak external knee flexion moment (TT, 0.15 ± 0.12 Nm/kg·m; AMP, 0.25 ± 0.12 Nm/kg·m; control, 0.25 ± 0.16 Nm/kg·m) (P = .032) and posterior shear force (TT, 0.64 ± 0.55 N/kg; AMP, 1.10 ± 0.58 N/kg; control, 1.35 ± 0.55 N/kg) (P = .024) in the TT group compared with controls, but not in the AMP group. Moreover, a significantly greater medial shear force was found in the TT group during the late stance phase (TT, 1.08 ± 0.32 N/kg; AMP, 0.89 ± 0.26 N/kg; control, 0.83 ± 0.22 N/kg) (P = .038). A greater peak external knee adduction moment was found in both ACL groups during the early stance phase (TT, 0.25 ± 0.07 Nm/kg·m; AMP, 0.25 ± 0.07 Nm/kg·m; control, 0.19 ± 0.05 Nm/kg·m) (P < .01).

CONCLUSION

Knee joint kinetic changes are seen within months (~10 months) after ACLR. This study revealed significant relationships between femoral tunnel orientation and postoperative knee joint flexion moment and posterior shear force during walking. The AMP technique provides better restoration of these knee kinetic parameters compared with the TT technique at this postoperative time point.

CLINICAL RELEVANCE

The femoral tunnel angle measured from plain radiographs can be used as an important metric of postoperative knee joint kinetics. This information provides a better understanding of the knee joint's biomechanical environment after ACLR using commonly used single-bundle techniques.

Principles of postoperative anterior cruciate ligament rehabilitation

It is known that anterior cruciate ligament (ACL) reconstruction needs to be combined with detailed postoperative rehabilitation in order for patients to return to their pre-injury activity levels, and that the rehabilitation process is as important as the reconstruction surgery. Literature studies focus on how early in the postoperative ACL rehabilitation period rehabilitation modalities can be initiated. Despite the sheer number of studies on this topic, postoperative ACL rehabilitation protocols have not been standardized yet. Could common, “ossified” knowledge or modalities really prove themselves in the literature? Could questions such as “is postoperative brace use really necessary?”, “what are the benefits of early restoration of the range of motion (ROM)?”, “to what extent is neuromuscular electrical stimulation (NMES) effective in the protection from muscular atrophy?”, “how early can proprioception training and open chain exercises begin?”, “should strengthening training start in the immediate postoperative period?” be answered for sure? My aim is to review postoperative brace use, early ROM restoration, NMES, proprioception, open/closed chain exercises and early strengthening, which are common modalities in the very comprehensive theme of postoperative ACL rehabilitation, on the basis of several studies (Level of Evidence 1 and 2) and to present the commonly accepted ways they are presently used. Moreover, I have presented the objectives of postoperative ACL rehabilitation in tables and recent miscellaneous studies in the last chapter of the paper.

Neural and morphological adaptations of vastus lateralis and vastus medialis muscles to isokinetic eccentric training

Vastus lateralis (VL) and vastus medialis (VM) are frequently targeted in conditioning/rehabilitation programs due to their role in patellar stabilization during knee extension. This study assessed neural and muscular adaptations in these two muscles after an isokinetic eccentric training program. Twenty healthy men underwent a four-week control period followed by a 12-week period of isokinetic eccentric training. Ultrasound evaluations of VL and VM muscle thickness at rest and electromyographic evaluations during maximal isometric tests were used to assess the morphological and neural properties, respectively. No morphological and neural changes were found throughout the control period, whereas both muscles showed significant increases in thickness (VL = 6.9%; p < .001 and VM = 15.8%; p < .001) post-training. Significant increases in muscle activity were observed in VM (47.8%; p = .003), but not in VL (19.8%; p > .05) post-training. Isokinetic eccentric training produces neural and greater morphological adaptations in VM compared to VL, which shows that synergistic muscles respond differently to an eccentric isokinetic strength training program

The role of eccentric exercise in sport injuries rehabilitation

INTRODUCTION

Sports injuries frequently involve tendons, muscles and ligaments. The variable outcome of surgery and medical treatment support early functional treatments. Eccentric exercise (EE) showed effectiveness in the management of Achilles tendinopathy (AT), patellar tendinopathy (PT) and lateral epicondyle tendinopathy (LET). Preliminary results of EE in other tendinopathies and sports injuries suggest its wide prescription in the sport rehabilitation field.

SOURCES OF DATA

A comprehensive search of PubMed, Web of Science, the Cochrane Collaboration Database, Physiotherapy Evidence Database (PEDro), Evidence Based Medicine (EBM) Search review, National Guidelines, Scopus and Google Scholar was performed using keywords such as 'eccentric exercise', 'sports injuries rehabilitation', 'tendinopathy', 'hamstrings strain' 'adductor injuries' and 'ACL reconstruction rehabilitation'.

AREAS OF AGREEMENT

EE, alone or associated with other therapies, represents a feasible, cost-effective and successful tool in the treatment of well-known targets and might be promising in shoulder tendinopathy, adductor-related groin pain, hamstring strains, and ACL rehabilitation.

AREA OF CONTROVERSY

The lack of standardization of protocols, the variable amount, quality and follow-up of studies, the different anatomy and pathophysiology of the therapeutic targets limit the evidence of applicability of EE to sports injuries.

GROWING POINTS

The role of pathology and biomechanics in the response to EE should be further investigated.

AREAS TIMELY FOR DEVELOPING RESEARCH

New randomized controlled trials should test the effectiveness of standardized EE regimens to various sites of sports injuries.

Quadriceps function following ACL reconstruction and rehabilitation: implications for optimisation of current practices

PURPOSE

To determine the most effective practices for quadriceps strengthening after ACL reconstruction.

METHODS

An electronic search has been performed for the literature appearing from January 1990 to January 2012. Inclusion criteria were articles written in English, German or Dutch with unilateral ACL-reconstructed patients older than 13 years, RCT rehabilitation programmes containing muscle strengthening, protocol described in detail and time frame of measurements reported. Quadriceps muscle strength and patient-reported outcomes were the endpoints. Included studies were assessed on their methodological quality using the CONSORT Checklist.

RESULTS

From 645 identified studies, 10 met the inclusion criteria. Seven studies found an increase in quadriceps strength after intervention programmes regardless of type of training. An eccentric exercise programme showed significantly better values for isometric quadriceps strength compared to a concentric exercise programme. The Tegner activity scale showed a significant increase in activity level for all training programmes. The Cincinnati Knee Rating System showed significant improvements in particular for the neuromuscular training group.

CONCLUSIONS

The evidence from this review indicates that eccentric training may be most effective to restore quadriceps strength, but full recovery may not be achieved with current rehabilitation practices. Neuromuscular training incorporating motor learning principles should be added to strengthening training to optimise outcome measurements.

LEVEL OF EVIDENCE

II.

Relationship between isokinetic strength and tibiofemoral joint space width changes after anterior cruciate ligament reconstruction

BACKGROUND

It has been hypothesized that quadriceps muscle weakness is directly associated with the onset and progression of posttraumatic osteoarthritis after anterior cruciate ligament (ACL) injury and reconstruction (ACLR). This relationship, however, has not been studied with a prospective approach that includes the use of tibiofemoral joint space width difference (JSW-D) measurements to characterize the onset of posttraumatic osteoarthritis before the clinical manifestation of the disease.

PURPOSE

To assess the relationship between thigh muscle strength and JSW-D at presurgery baseline and at 1- and 4-year follow-up after ACLR compared with healthy, noninjured participants of similar sex, age, body mass index, and activity level.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 39 unilateral ACL-injured patients and 32 healthy controls were followed prospectively. During each follow-up, JSW, isokinetic knee strength, single-legged hop, and clinical- and patient-oriented outcomes were assessed. At final follow-up, ACL-injured participants who had JSW-D values (considered as the injured minus normal knee) that were less than the 95% confidence interval of controls were considered to be in the ACLR-narrow group, while those with JSW-D values that fell within the confidence intervals were in the ACLR-normal group. Relationships were evaluated between ACLR groups and controls via multilevel regression, as well as Kruskal-Wallis tests for between-group comparisons at 4-year follow-up.

RESULTS

At 4-year follow-up, 30 participants (79%) were in the ACLR-normal group and 8 (21%) were in the ACLR-narrow group. At baseline, the extension, flexion, and extension/flexion ratio strength values for both ACLR groups were significantly lower than those of controls (P ≤ .05), while the ACLR-narrow group had significantly lower extension strength at 60 and 180 deg/s (P = .04 and .03, respectively), as well as extension/flexion ratio at 60 deg/s (P = .04) in comparison with the ACL-normal group. At 4-year follow-up, 60 deg/s extension strength deficits persisted in the ACLR-narrow group compared with controls and ACLR-normal participants (P = .01 and .04, respectively). Flexion strength at 180 and 300 deg/s was also significantly lower in the ACLR-narrow group compared with ACLR-normal (P = .02 and .04, respectively), as was single-legged hop distance (P = .04).

CONCLUSION

Strength deficits present within months after ACL injury and persist through 4 years after ACLR in participants with significantly narrowed JSW-D, compared with ACLR participants with normal JSW-D and controls. This study revealed a significant relationship between quadriceps strength loss that occurred soon after injury and JSW narrowing.

The role of muscle activation in cruciate disease

Traditional investigations into the etiopathogenesis of canine cranial cruciate ligament (CCL) disease have focused primarily on the biological and mechanical insults to the CCL as a passive stabilizing structure of the stifle. However, with recent collaboration between veterinarians and physical therapists, an increased focus on the role of muscle activity and aberrant motor control mechanisms associated with anterior cruciate ligament (ACL) injuries and rehabilitation in people has been transferred and applied to dogs with CCL disease. Motor control mechanisms in both intact and cruciate-deficient human knees may have direct translation to canine patients, because the sensory and motor components are similar, despite moderate anatomic and biomechanical differences. Components of motor control, such as muscle recruitment and the coordination and amplitudes of activation are strongly influenced by afferent proprioceptive signaling from peri- and intra-articular structures, including the cruciate ligaments. In people, alterations in the timing or amplitude of muscle contractions contribute to uncoordinated movement, which can play a critical role in ACL injury, joint instability and the progression of osteoarthritis (OA). A better understanding of motor control mechanisms as they relate to canine CCL disease is vitally important in identifying modifiable risk factors and applying preventative measures, for development of improved surgical and rehabilitative treatment strategies. The purpose of this review article is to analyze the influence of altered motor control, specifically pelvic limb muscle activation, in dogs with CCL disease as evidenced by mechanisms of ACL injury and rehabilitation in people.

Construction of an Isokinetic Eccentric Cycle Ergometer for Research and Training

Eccentric cycling serves a useful exercise modality in clinical, research, and sport training settings. However, several constraints can make it difficult to use commercially available eccentric cycle ergometers. In this technical note, we describe the process by which we built an isokinetic eccentric cycle ergometer using exercise equipment modified with commonly available industrial parts. Specifically, we started with a used recumbent cycle ergometer and removed all the original parts leaving only the frame and seat. A 2.2 kW electric motor was attached to a transmission system that was then joined with the ergometer. The motor was controlled using a variable frequency drive, which allowed for control of a wide range of pedaling rates. The ergometer was also equipped with a power measurement device that quantified work, power, and pedaling rate and provided feedback to the individual performing the exercise. With these parts along with some custom fabrication, we were able to construct an isokinetic eccentric cycle ergometer suitable for research and training. This paper offers a guide for those individuals who plan to use eccentric cycle ergometry as an exercise modality and wish to construct their own ergometer.