Cross-education for improving strength and mobility after distal radius fractures: a randomized controlled trial

Cross-education of lower limb muscle strength following resistance exercise training in males and females: A systematic review and meta-analysis

Cross-education describes the training of one limb that leads to performance enhancements in the contralateral untrained limb, driven by neural changes rather than muscle adaptation. In this systematic review and meta-analysis, we aimed to evaluate the efficacy of cross-education (vs. a control group) via resistance exercise training (RET) for improving muscle strength in the untrained lower limb of healthy males and females. A literature search from inception to September 2023 was conducted using MEDLINE (via PubMed), the Cochrane Library (CENTRAL), Web of Science (Core Database), Scopus, EBSCO-host, and Ovid-EMBASE. Independent screening, data extraction and quality assessment were conducted. The measured outcomes were change in one-repetition maximum (1-RM) load, maximum voluntary contraction (MVC), and concentric, eccentric and isometric peak torque. Change in muscle structure (pennation angle and muscle thickness) was also analysed. A total of 29 studies were included. The pooled effect size from the random-effects model shows that cross-education significantly increased 1-RM compared to the control group (standardised mean difference (SMD): 0.59, 95% CI: 0.22-0.97; P = 0.002). Cross-education also significantly improved MVC (SMD: 0.55, 95% CI: 0.16-0.94; P = 0.006), concentric (SMD: 0.61, 95% CI: 0.39-0.84; P < 0.00001), eccentric (SMD: 0.39, 95% CI: 0.13-0.64; P = 0.003) and isometric (SMD: 0.45, 95% CI: 0.26-0.64; P < 0.00001) peak torque, each compared to the control group. When RET was categorised as eccentric or concentric, subgroup analysis showed that only eccentric training was associated with significantly increased isometric peak torque via cross-education (SMD: 0.37, 95% CI: 0.13-0.61; P = 0.003) (concentric, SMD: 0.33, 95% CI: -0.09 to 0.74; P = 0.12). This systematic review and meta-analysis emphasise the potency of cross-education for improving lower limb muscle strength. These findings have potential implications for clinical situations of impaired unilateral limb function (e.g., limb-casting or stroke). Future work exploring the mechanisms facilitating these enhancements will help to develop optimised rehabilitation protocols.

Distal Radius Fracture Rehabilitation

Distal radius fracture (DRF) is arguably the most common upper extremity fracture resulting from a fall accident. These clinical practice guidelines (CPG) were developed to guide all aspects of the management of DRF by physical therapists and other rehabilitation practitioners, such as certified hand therapists. This CPG employed a systematic review methodology to locate, appraise, and synthesize contemporary evidence while developing practice recommendations for determining the prognosis of outcomes, examination, and interventions while managing individuals with DRF. The quality of the primary studies found in the literature search was appraised using standardized tools. The strength of the available evidence for a particular practice domain (e.g., prognosis or intervention) was graded as strong, moderate, weak, or conflicting, where such gradings guided the level of obligation for each practice recommendation. Lastly, the CPG also provided the gaps in the evidence pool for the rehabilitation of DRF that future research efforts can address. J Orthop Sports Phys Ther 2024;54(9):CPG1-CPG78. doi:10.2519/jospt.2024.0301.

The Functional Dexterity Test in Adult Populations: An Exploration of a Simplified Test Protocol and Parameters Guided by Statistical Outcomes

BACKGROUND

The Functional Dexterity Test (FDT) is a standardized assessment used to quantify dexterity, in-hand manipulation, related to function. Recommendations to modify the scoring have been proposed to eliminate penalties, adapt the test protocol, and change the outcome parameter. A new psychometrically sound scoring system has been used in the pediatric population; however, research in the adult population requires exploration.

PURPOSE

The purpose of this study was to test if alterations in test administration, outcome recording, and outcome parameters show predictive validity for measured outcomes for age, ethnicity, and self-identified gender. The new method of administering the FDT eliminates penalties for improper performance and uses a score of speed derived from the timed score. It was theorized that eliminating assessment of reported errors in quality of movement in the quantitative scoring may improve the test validity.

STUDY DESIGN

Clinical Measurement.

METHODS

The FDT was administered to 148 healthy adults aged between 18 and 78 years. No penalties were included in the quantitative scoring. Age, self-identified gender, ethnicity, and self-reported hand dominance were recorded. Time to complete the test was measured in seconds per usual protocol. The result was recorded as time and calculated as speed. Linear regression was performed to predict FDT speed from age, hand dominance, and self-identified gender.

RESULTS

The three predictors (age, hand dominance, and gender) associated with a linear decline in dexterity were significant (p ≤0.02). Dexterity showed a linear decline with age, and participants showed faster speeds with the dominant hand. Gender was a significant predictor of speed, with males having faster speeds by an average of 0.047 pegs per second (p = 0.01).

CONCLUSIONS

Scores using a simplified administration and speed as an outcome showed moderate predictive validity with age, gender, and the dominant hand used in this adult population. Future research exploring relationships with activities of daily living is needed.

Exercise-based intervention as a nonsurgical treatment for patients with carpal instability: A case series

BACKGROUND

Although the important roles of proprioception and neuromuscular control in carpal instabilities under laboratory conditions have been recognized, only a few studies have translated this knowledge into a routine clinical practice.

PURPOSE

This study aimed to evaluate the results of a personalized rehabilitation in patients with carpal instability on functionality and pain intensity.

STUDY DESIGN

This was a case series study.

METHODS

This case series included 39 adults (mean age: 38.2 ± 14.0 years; 16/23 females/males) diagnosed with carpal instability (radial or ulnar) with indication for orthopedic treatment. The disabilities of the arm, shoulder, and hand questionnaire was used to assess upper limb functionality. Pain perception was assessed using a visual analog scale. Exercise-based physiotherapy interventions were performed according to the clinical needs of the patients for at least 6 weeks (2-3 sessions per week). For the treatment of radial instability (n = 13), strengthening exercises of the abductor pollicis longus, extensor carpi radialis longus, flexor carpi radialis, and pronator quadratus muscles were prescribed. For the treatment of ulnar instability (n = 24), extensor carpi ulnaris and pronator quadratus were trained. All patients underwent proprioceptive training in open kinetic chain and closed kinetic chain, as well as strengthening of the unaffected hand. Changes before and after treatment were compared using the nonparametric Wilcoxon signed rank test.

RESULTS

A significant improvement with a large effect size in disabilities of the arm, shoulder, and hand (P < .001; d = 2.9) and visual analog scale (P < .001; d = 3.2) scores were obtained after treatment. Moreover, the changes were greater than the minimal clinically important difference of 10.8 and 1.4, respectively. Similar results were found when patients with radial instability and ulnar instability were analyzed separately.

CONCLUSIONS

Personalized training with specific proprioception and strengthening exercises produces improvements in functionality and pain perception in our cohort of people with carpal instability. These results highlight the importance of multicomponent exercise in the treatment of wrist instability. Future randomized clinical trials should further investigate the effectiveness of this protocol.

Effect of leg dominance on ipsilateral and contralateral limb training adaptation in middle-aged women after unilateral sensorimotor and resistance exercise training

The aim was to examine the directionality of global training effects in middle-aged women after unilateral training.

Thirty-nine middle-aged female volunteers (59.4 ± 5.4 years) were randomly assigned to one of three groups: 1. Unilateral Dominant Lower Limb Training (UDLT); 2. Unilateral Non-Dominant Lower Limb Training (UNDLT) or 3. Control group. Outcome measures assessing isometric strength, static and dynamic balance were recorded at baseline, and 1 week after 12 weeks (post-test) of training or no-intervention.

The net cross education adaptation changes of the contralateral quadriceps isometric maximum voluntary (MVC) force (F2,34 = 4.33; p = 0.022), Stork balance score (F2,34 = 4.26; p = 0.023) and the Star Excursion Balance test score (F2,34 = 11.80; p = 0.001) were asymmetrical in the UNDLT group and on average, exceeded the UDLT group.

The results demonstrated asymmetrical cross education training adaptations with unilateral training of non-dominant leg (UNDLT) to contralateral homologous and heterologous muscles, with the exception of knee flexor MVC. The results of this study provide a novel exercise or rehabilitation strategy that can be employed when one of the limbs is affected.

A randomized controlled trial on the effectiveness of mirror therapy in improving strength, range of movement and muscle activity, in people with carpal tunnel syndrome

BACKGROUND

There is little information on the potential effects of mirror therapy (MT) on motor recovery in individuals with Carpal Tunnel Syndrome (CTS).

PURPOSE

To compare the effectiveness of a MT protocol versus a therapeutic exercise (TE) protocol, in improving strength, range of motion (ROM), muscle activity, pain, and functionality in patients with CTS.

STUDY DESIGN

Randomized clinical trial.

METHODS

Thirty-nine participants with unilateral CTS were divided into two groups: (i) MT group (n = 20) that followed an exercise protocol applied to the unaffected hand reflected in a mirror, and (ii) TE group (n = 19) that followed the same exercise protocol using the unaffected hand but without a mirror. Strength, wrist ROM, muscle activity, pain and functionality, were assessed at baseline (T0), after treatment (T1) and one month after treatment (T2).

RESULTS

At T1, the MT group showed significantly higher wrist flexion-extension ROM compared to TE (p = 0.04, d = 0.8), maintained at T2 (p = 0.02, d = 0.8). No significant changes were observed in ulnar-radius deviation, pronosupination, or fatigue following either MT or TE (p > 0.05). MT exhibited enhanced handgrip strength at T1 (p = 0.001, d = 0.7), as well as an increase in the extensor carpi radialis (ECR) and flexor carpi radialis (FCR) maximum muscle activity (p = 0.04, d = 1.0; p = 0.03, d = 0.4). At T1, both groups decreased pain (p = 0.002, d = 1.1; p = 0.02, d = 0.7), and improved functionality (p < 0.001, d = 0.8; p = 0.01, d = 0.5) (MT and TE respectively).

DISCUSSION

MT led to enhancements in wrist flexion-extension movement, handgrip strength and functionality unlike TE. MT notably increased muscle activity, particularly in the ECR and FCR muscles.

CONCLUSIONS

MT is a favorable strategy to improve wrist flexion-extension ROM, handgrip strength, ECR and FCR muscle activity, and functionality in people with unilateral CTS.

Exercise prescription and strategies to promote the cross-education of strength: a scoping review

The cross-education of strength is moderated by exercise design and prescription in clinical and non-clinical populations. This review synthesizes the available evidence regarding exercise design strategies for unilateral resistance training and provides evidence-based recommendations for the prescription of unilateral training to maximize the cross-education of strength. Greater insights regarding the timing and effectiveness of cross-education interventions in clinical scenarios will strengthen the use of unilateral resistance training for individuals who may benefit from its use.

Effects of Unilateral Eccentric versus Concentric Training of Nonimmobilized Arm during Immobilization

INTRODUCTION

The present study tested the hypothesis that eccentric training (ET) of nonimmobilized arm would attenuate negative effects of immobilization and provide greater protective effects against muscle damage induced by eccentric exercise after immobilization, when compared with concentric training (CT).

METHODS

Sedentary young men were placed to ET, CT, or control group ( n = 12 per group), and their nondominant arms were immobilized for 3 wk. During the immobilization period, the ET and CT groups performed five sets of six dumbbell curl eccentric-only and concentric-only contractions, respectively, at 20%-80% of maximal voluntary isometric contraction (MVCiso) strength over six sessions. MVCiso torque, root-mean square (RMS) of electromyographic activity during MVCiso, and bicep brachii muscle cross-sectional area (CSA) were measured before and after immobilization for both arms. All participants performed 30 eccentric contractions of the elbow flexors (30EC) by the immobilized arm after the cast was removed. Several indirect muscle damage markers were measured before, immediately after, and for 5 d after 30EC.

RESULTS

ET increased MVCiso (17% ± 7%), RMS (24% ± 8%), and CSA (9% ± 2%) greater ( P < 0.05) than CT (6% ± 4%, 9% ± 4%, 3% ± 2%) for the trained arm. The control group showed decreases in MVCiso (-17% ± 2%), RMS (-26% ± 6%), and CSA (-12% ± 3%) for the immobilized arm, but these changes were attenuated greater ( P < 0.05) by ET (3% ± 3%, -0.1% ± 2%, 0.1% ± 0.3%) than CT (-4% ± 2%, -4% ± 2%, -1.3% ± 0.4%). Changes in all muscle damage markers after 30EC were smaller ( P < 0.05) for the ET and CT than the control group, and ET than the CT group (e.g., peak plasma creatine kinase activity: ET, 860 ± 688 IU·L -1 ; CT, 2390 ± 1104 IU·L -1 ; control, 7819 ± 4011 IU·L -1 ).

CONCLUSIONS

These results showed that ET of the nonimmobilized arm was effective for eliminating the negative effects of immobilization and attenuating eccentric exercise-induced muscle damage after immobilization.

To assess the effects of cross-education on strength and motor function in post stroke rehabilitation: a systematic literature review and meta-analysis

BACKGROUND

Cross-education refers to the increase in motor output of the untrained limb following unilateral training of the opposite limb. Cross education has been shown to be beneficial in clinical settings.

OBJECTIVES

This systematic literature and meta-analysis aims to assess the effects of cross-education on strength and motor function in post stroke rehabilitation.

DATA SOURCES

MEDLINE, CINAHL, Cochrane Library, PubMed, PEDro, Web of Science, ClinicalTrails.gov and Cochrane Central registers were searched up to 1st October 2022.

STUDY SELECTION

Controlled trials using unilateral training of the less affected limb in individuals diagnosed with stroke and English language.

DATA SYNTHESIS

Methodological quality was assessed using Cochrane Risk-of-Bias tools. Quality of evidence was evaluated using Grading of Recommendations Assessment, Development and Evaluation. Meta-analyses were performed using RevMan 5.4.1.

RESULTS

Five studies capturing 131 participants were included in the review and three studies capturing 95 participants were included in the meta-analysis. Cross education was shown to have a statistically and clinically significant effect on upper limb strength (p < 0.003; SMD 0.58; 95% CI 0.20-0.97; n = 117) and upper limb function (p = 0.04; SMD 0.40; 95% CI 0.02-0.77; n = 119).

LIMITATIONS

Small number of studies, with all studies identified as having some risk of bias. Quality of evidence graded 'low' due to limitations and imprecision.

CONCLUSION

Cross education may be beneficial in improving strength and motor function in the more affected upper limb post stroke. Further studies are needed as the research into the benefits of cross education in stroke rehabilitation is still limited. Systematic Review Registration Number: PROSPERO (CRD42020219058).

Effect of unilateral training and bilateral training on physical performance: A meta-analysis

Background: In Unilateral (UNI) exercises are more effective than bilateral (BI) exercises in improving athletic performance is debatable. Objectives: this meta-analysis investigated the effects of UNI and BI exercises on different effect indicators of jump ability, sprint ability, maximal force, change of direction ability, and balance ability. Data Sources: PubMed, Google Scholar, Web of science, CNKI, Proquest, Wan Fang Data. Study Eligibility Criteria: To be eligible for inclusion in the meta-analysis, the study had to be: 1) athletes; 2) UNI training and BI training; 3) the intervention period had to be more than 6 weeks and the intervention frequency had to be more than 2 times/week; 4) the outcome indicators were jumping ability, sprinting ability, maximum strength, and change of direction and balance. Study Appraisal and Synthesis Method: We used the random-effects model for meta-analyses. Effect sizes (standardized mean difference), calculated from measures of horizontally oriented performance, were represented by the standardized mean difference and presented alongside 95% confidence intervals (CI). Results: A total of 28 papers met the inclusion criteria, and Meta-analysis showed that UNI training was more effective than BI training in improving jumping ability (ES = 0.61.0.23 to 0.09; Z = 3.12, p = 0.002 < 0.01), sprinting ability (ES = -0.02, -0.03 to -0.01; Z = 2.73, p = 0.006 < 0.01), maximum strength (ES = 8.95,2.30 to 15.61; Z = 2.64, p = 0.008 > 0.05), change of direction ability (ES = -0.03, -0.06 to 0.00; Z = 1.90, p = 0.06 > 0.01) and balance ability (ES = 1.41,-0.62 to 3.44; Z = 1.36, p = 0.17 > 0.01). The results of the analysis of moderating variables showed that intervention period, intervention frequency and intervention types all had different indicators of effect on exercise performance. Conclusion: UNI training has a more significant effect on jumping and strength quality for unilateral power patterns, and BI training has a more significant effect on jumping and strength quality for bilateral power patterns.

Unilateral Strength Training Imparts a Cross-Education Effect in Unilateral Knee Osteoarthritis Patients

Background: Worldwide, 86 million individuals over the age of 20 were diagnosed with knee osteoarthritis (KOA) in 2020. Hallmark features of KOA are the loss in knee extensor strength, increasing knee pain severity, and deficits in functional performance. There is a critical need for the investigation into potential cost-effective therapeutic interventions in the treatment of KOA. A potential therapeutic option is the cross-education phenomenon. Methods: This was a non-blinded randomized control trial, with a 4-week intervention, with a pre, post and follow-up assessment (3 months post intervention). Outcome measures of isometric knee extensor strength, rectus femoris muscle thickness and neuromuscular activation were assessed at all-time points. Results: Compared to age-matched KOA controls, 4 weeks of unilateral strength training in end-stage KOA patients increased strength of the untrained affected KOA limb by 20% (p < 0.05) and reduced bilateral hamstring co-activation in the KOA intervention group compared to the KOA control group (p < 0.05). Conclusions: A 4-week-long knee extensor strength training intervention of the contralateral limb in a cohort with diagnosed unilateral KOA resulted in significant improvements to knee extensor strength and improved neuromuscular function of the KOA limb. Importantly, these results were maintained for 3 months following the intervention.

Overall Effects and Moderators of Rehabilitation in Patients With Wrist Fracture: A Systematic Review

OBJECTIVE

Wrist fractures constitute the most frequently occurring upper limb fracture. Many individuals report persistent pain and functional limitations up to 18 months following wrist fracture. Identifying which individuals are likely to gain the greatest benefit from rehabilitative treatment is an important research priority. This systematic review aimed to summarize effectiveness of rehabilitation after wrist fracture for pain and functional outcomes and identify potential effect moderators of rehabilitation.

METHODS

A comprehensive search of 7 databases (including MEDLINE, EMBASE, and the Physiotherapy Evidence Database) was performed for randomized controlled trials involving adults >50 years of age who sustained wrist fracture and had received 1 or more conservative treatments (eg, exercise/manual therapy, lifestyle, diet, or other advice). Study selection, data extraction, and risk-of-bias assessment were conducted independently by 2 reviewers. Results of included trials were summarized in a narrative synthesis.

RESULTS

A total of 3225 titles were screened, and 21 studies satisfying all eligibility criteria were reviewed. Over one-half of the included studies (n = 12) comprised physical therapist and/or occupational therapist interventions. Rehabilitative exercise/manual therapy was generally found to improve function and reduce pain up to 1 year after wrist fracture. However, effects were small, and home exercises were found to be comparable with physical therapist-led exercise therapy. Evidence for the effects of other nonexercised therapy (including electrotherapy, whirlpool) was equivocal and limited to the short term (<3 months). Only 2 studies explored potential moderators, and they did not show evidence of moderation by age, sex, or patient attitude of the effects of rehabilitation.

CONCLUSION

Effectiveness of current rehabilitation protocols after wrist fracture is limited, and evidence for effect moderators is lacking. Currently available trials are not large enough to produce data on subgroup effects with sufficient precision. To aid clinical practice and optimize effects of rehabilitation after wrist fracture, potential moderators need to be investigated in large trials or meta-analyses using individual participant data.

IMPACT

Many patients report persistent pain and functional limitations up to 18 months following wrist fracture. Effectiveness of current rehabilitation protocols after wrist fracture is limited and may be due to insufficient targeting of specific rehabilitation to individuals who are likely to benefit most. However, evidence for effect moderators is lacking within the currently available literature. To aid clinical practice and optimize effects of rehabilitation, investigating potential moderators of rehabilitation in individuals with wrist fracture via large trials or meta-analysis of individual participant data is research and policy imperative.

Does mental practice or mirror therapy help prevent functional loss after distal radius fracture? A randomized controlled trial

STUDY DESIGN

A randomized, single-blinded controlled trial.

INTRODUCTION

Therapy results after distal radius fractures (DRF) especially with older patients are often suboptimal. One possible approach for counteracting the problems are motor-cognitive training interventions such as Mental Practice (MP) or Mirror Therapy (MT), which may be applied in early rehabilitation without stressing the injured wrist.

PURPOSE OF THE STUDY

The aim of the study is to investigate the effects of MP and MT on wrist function after DRF. The pilot study should furthermore provide information about the feasibility of these methods.

METHODS

Thirty-one women were assigned either to one of the two experimental groups (MP, MT) or to a control group (relaxation intervention). The participants completed a training for six weeks, administered at their homes. Measurements were taken at four times (weeks 0, 3, 6 and 12) to document the progression in subjective function (PRWE, QuickDASH) and objective constraints of the wrist (ROM, grip strength) as well as in health-related quality of life (EQ-5D).

RESULTS

The results indicated that both experimental groups showed higher improvements across the intervention period compared to the control group; e.g. PRWE: MT 74.0%, MP 66.2%, CG 56.9%. While improvements in grip strength were higher for the MP group, the MT group performed better in all other measures. However, time by group interactions approached significance at best; e.g. ROM: P = .076; η_p² = .141.

CONCLUSION

The superiority of MP as well as MT supports the simulation theory. Motor-cognitive intervention programs are feasible and promising therapy supplements, which may be applied in early rehabilitation to counteract the consequences of immobilization without stressing the injured wrist.

Rehabilitation in Triangular Fibrocartilage Complex Injuries: Treatment Algorithm

Injuries to the triangular fibrocartilage complex (TFCC) can lead to instability of the distal radioulnar joint (DRUJ). In fact, they are the most frequent cause of it. But, in other cases, depending on the type of injury, the DRUJ remains stable. This will condition different types of treatments, from conservative management to the different options of surgical treatment. Since a controversy persists regarding the management of these lesions, our purpose is to disclose the foundations of the rehabilitation treatment and propose an algorithm of treatment according to the different types of injuries and their repairs.

1894 revisited: Cross-education of skilled muscular control in women and the importance of representation

In 1894 foundational work showed that training one limb for “muscular power” (i.e. strength) or “muscular control” (i.e. skill) improves performance in both limbs. Despite that the original data were exclusively from two female participants (“Miss Smith” and “Miss Brown”), in the decades that followed, such “cross-education” training interventions have focused predominantly on improving strength in men. Here, in a female cohort, we revisit that early research to underscore that training a task that requires precise movements in a timely fashion (i.e. “muscular control”) on one side of the body is transferred to the contralateral untrained limb. With unilateral practice, women reduced time to completion and the number of errors committed during the commercially available game of Operation^® Iron Man 2 with both limbs. Modest reductions in bilateral Hoffmann (H-) reflex excitability evoked in the wrist flexors suggest that alterations in the spinal cord circuitry may be related to improvements in performance of a fine motor task. These findings provide a long overdue follow-up to the efforts of Miss Theodate L. Smith from more than 125 years ago, highlight the need to focus on female participants, and advocate more study of cross-education of skilled tasks.

A scoping review of the contralateral effects of unilateral peripheral stimulation on neuromuscular function

It is known that resistance exercise using one limb can affect motor function of both the exercised limb and the unexercised contralateral limb, a phenomenon termed cross-education. It has been suggested that cross-education has clinical implications, e.g. in rehabilitation for orthopaedic conditions or post-stroke paresis. Much of the research on the contralateral effect of unilateral intervention on motor output is based on voluntary exercise. This scoping review aimed to map the characteristics of current literature on the cross-education caused by three most frequently utilised peripheral neuromuscular stimulation modalities in this context: electrical stimulation, mechanical vibration and percutaneous needling, that may direct future research and translate to clinical practice. A systematic search of relevant databases (Ebsco, ProQuest, PubMed, Scopus, Web of Science) through to the end of 2020 was conducted following the PRISMA Extension for Scoping Review. Empirical studies on human participants that applied a unilateral peripheral neuromuscular stimulation and assessed neuromuscular function of the stimulated and/or the unstimulated side were selected. By reading the full text, the demographic characteristics, context, design, methods and major findings of the studies were synthesised. The results found that 83 studies were eligible for the review, with the majority (53) utilised electrical stimulation whilst those applied vibration (18) or needling (12) were emerging. Although the contralateral effects appeared to be robust, only 31 studies claimed to be in the context of cross-education, and 25 investigated on clinical patients. The underlying mechanism for the contralateral effects induced by unilateral peripheral stimulation remains unclear. The findings suggest a need to enhance the awareness of cross-education caused by peripheral stimulation, to help improve the translation of theoretical concepts to clinical practice, and aid in developing well-designed clinical trials to determine the efficacy of cross-education therapies.

Motor effects of movement representation techniques and cross-education: a systematic review and meta-analysis

INTRODUCTION

The objective was to assess the impact of movement representation techniques (MRT) through motor imagery (MI), action observation (AO) and visual mirror feedback (VMF) and cross-education training (CE) on strength, range of motion (ROM), speed, functional state and balance during experimental immobilization processes in healthy individuals, in patients with injuries that did not require surgery and in those with surgical processes that did or did not require immobilization.

EVIDENCE ACQUISITION

MEDLINE, EMBASE, CINAHL and Google Scholar were searched. Thirteen meta-analyses were conducted.

EVIDENCE SYNTHESIS

Regarding the immobilized participants, in the healthy individuals, MI showed significant results regarding maintenance of strength and ROM, with low-quality evidence. Regarding the process with no immobilization, VMF and MI techniques showed significant changes in maintaining ROM in patients with injury without surgery, with very low-quality evidence. Results had shown that MI demonstrated significantly higher maintenance of strength and speed in patients undergoing surgery, with low-quality evidence. No significant results were found in ROM. Low-quality evidence showed better results in AO plus usual care compared with usual treatment in isolation with respect to maintenance of functional state and balance. CE training demonstrated maintenance of strength in patients undergoing surgery, with moderate evidence; however, not in healthy experimentally immobilized individuals. VMF did not show significant results in maintaining ROM after surgery without immobilization, nor did MI in maintaining strength after surgery and immobilization.

CONCLUSIONS

MRT and CE training have been shown to have a significant impact on the improvement of various motor variables and on physical maintenance in general.

Neural mechanisms mediating cross education: With additional considerations for the ageing brain

CALVERT, G.H.M., and CARSON, R.G. Neural mechanisms mediating cross education: With additional considerations for the ageing brain. NEUROSCI BIOBEHAV REV 21(1) XXX-XXX, 2021. - Cross education (CE) is the process whereby a regimen of unilateral limb training engenders bilateral improvements in motor function. The contralateral gains thus derived may impart therapeutic benefits for patients with unilateral deficits arising from orthopaedic injury or stroke. Despite this prospective therapeutic utility, there is little consensus concerning its mechanistic basis. The precise means through which the neuroanatomical structures and cellular processes that mediate CE may be influenced by age-related neurodegeneration are also almost entirely unknown. Notwithstanding the increased incidence of unilateral impairment in later life, age-related variations in the expression of CE have been examined only infrequently. In this narrative review, we consider several mechanisms which may mediate the expression of CE with specific reference to the ageing CNS. We focus on the adaptive potential of cellular processes that are subserved by a specific set of neuroanatomical pathways including: the corticospinal tract, corticoreticulospinal projections, transcallosal fibres, and thalamocortical radiations. This analysis may inform the development of interventions that exploit the therapeutic utility of CE training in older persons.

Cross-education and detraining effects of eccentric vs. concentric resistance training of the elbow flexors

Background

Unilateral resistance training increases the strength of the contralateral non-trained homologous muscles known as the cross-education effect. We tested the hypothesis that unilateral eccentric resistance training (ET) would induce greater and longer-lasting cross-education effect when compared with concentric resistance training (CT).

Methods

Young (20–23 y) participants were allocated to ET (5 males, 4 females) or CT (5 males, 4 females) group that performed unilateral progressive ET or CT of the elbow flexors, twice a week for 5 weeks (10 sessions) followed by a 5-week detraining, and control group (7 males, 6 females) that did not perform any training. Maximum voluntary isometric contraction torque of the elbow flexors (MVIC), one-repetition maximum of concentric dumbbell curl (1-RM), and biceps brachii and brachialis muscle thickness (MT) were measured from the trained and non-trained arms before, several days after the last training session, and 5 weeks later. A ratio between the trained and non-trained arms for the change in MVIC or 1-RM from pre- to post-training (cross-body transfer ratio) was compared between ET and CT groups.

Results

The control group did not show significant changes in any variables. Both ET and CT increased (P < 0.05) MVIC (22.5 ± 12.3 % vs. 26.0 ± 11.9 %) and 1-RM (28.8 ± 6.6 % vs. 35.4 ± 12.9 %) of the trained arm without a significant difference between groups. MVIC was maintained after detraining for ET but returned to the baseline for CT, and 1-RM was maintained after detraining for both ET and CT. For the non-trained arm, MVIC (22.7 ± 17.9 % vs. 12.2 ± 10.2 %) and 1-RM (19.9 ± 14.6 % vs. 24.0 ± 10.6 %) increased similarly (P > 0.05) after ET and CT, and MVIC returned to the baseline after detraining, but 1-RM was maintained for both groups. An increase (P < 0.05) in MT was found only after ET for the trained arm (7.1 ± 6.1 %). The cross-body transfer ratio for MVIC was greater (P < 0.05) for ET (90.9 ± 46.7 %) than CT (49.0 ± 30.0 %).

Conclusions

These results did not support the hypothesis and showed similar changes in the most of the variables between ET and CT for the trained and non-trained arms, and strong cross-education effects on MVIC and 1-RM, but less detraining effect after ET than CT on MVIC of the trained arm.

Trial registration

University Hospital Medical Information Network Clinical Trials Registry (UMIN000044477; Jun 09, 2021).

Set Configuration in Strength Training Programs Modulates the Cross Education Phenomenon

ABSTRACT

Fariñas, J, Mayo, X, Giraldez-García, MA, Carballeira, E, Fernandez-Del-Olmo, M, Rial-Vazquez, J, Kingsley, JD, and Iglesias-Soler, E. Set configuration in strength training programs modulates the cross education phenomenon. J Strength Cond Res 35(9): 2414-2420, 2021-This study aimed to compare the strength gains in the nontrained arm after 2 independent unilateral training programs differing in the set configuration. Thirty-five subjects were randomly assigned to 3 groups: traditional training (TT; n = 12), cluster training (CT; n = 11), or control (CON; n = 12). The experimental groups performed a 5-week training program of a unilateral biceps curl exercise with the dominant limb using the 10 repetition maximum (10RM) load. Traditional training performed 5 sets of 6 repetitions and 135 seconds of rest between sets. Cluster training completed 30 repetitions with 18.5 seconds of rest between each repetition. Anthropometry (ANT), muscle thickness (MT), 1RM, the number of repetitions with 10RM (n10RM), and isometric maximal voluntary contraction (MVC) were measured before and after the intervention. Regarding the nontrained arm, TT improved 1RM (7.3%, p < 0.001). No changes were observed in CT. Regarding the trained arm, TT improved 1RM (9.1%, p < 0.001), n10RM (p = 0.005), and MVC (p = 0.011), whereas CT only showed a trend for improvement of 1RM (3.4%, p = 0.052). These results suggest that when total volume and repetition-to-rest ratio are equated, a more fatiguing set configuration causes a higher effect on the non-trained limb.

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.

Contralateral Effects of Unilateral Strength and Skill Training: Modified Delphi Consensus to Establish Key Aspects of Cross-Education

Background

Cross-education refers to increased motor output (i.e., force generation, skill) of the opposite, untrained limb following a period of unilateral exercise training. Despite extensive research, several aspects of the transfer phenomenon remain controversial.

Methods

A modified two-round Delphi online survey was conducted among international experts to reach consensus on terminology, methodology, mechanisms of action, and translational potential of cross-education, and to provide a framework for future research.

Results

Through purposive sampling of the literature, we identified 56 noted experts in the field, of whom 32 completed the survey, and reached consensus (75% threshold) on 17 out of 27 items.

Conclusion

Our consensus-based recommendations for future studies are that (1) the term ‘cross-education’ should be adopted to refer to the transfer phenomenon, also specifying if transfer of strength or skill is meant; (2) functional magnetic resonance imaging, short-interval intracortical inhibition and interhemispheric inhibition appear to be promising tools to study the mechanisms of transfer; (3) strategies which maximize cross-education, such as high-intensity training, eccentric contractions, and mirror illusion, seem worth being included in the intervention plan; (4) study protocols should be designed to include at least 13–18 sessions or 4–6 weeks to produce functionally meaningful transfer of strength, and (5) cross-education could be considered as an adjuvant treatment particularly for unilateral orthopedic conditions and sports injuries. Additionally, a clear gap in views emerged between the research field and the purely clinical field.

The present consensus statement clarifies relevant aspects of cross-education including neurophysiological, neuroanatomical, and methodological characteristics of the transfer phenomenon, and provides guidance on how to improve the quality and usability of future cross-education studies.

Electronic supplementary material

The online version of this article (10.1007/s40279-020-01377-7) contains supplementary material, which is available to authorized users.

The adjunctive benefits of mirror cross education on kinetic chain exercise approach in volleyball athletes with scapular dyskinesis

BACKGROUND

Volleyball players as overhead athletes have the highest risk of developing Scapular Dyskinesis. The kinetic chain exercise-approach has gained a lot of attention because of its claims to provide an improved motor control and scapular kinematics. A form of cross exercise, known as mirror therapy, may enhance the effects of a Kinetic-Chain-Approach on scapular posture, upper and lower limb performance. The aim of this study was to investigate the adjunctive benefits of Mirror-Cross-Education in a Kinetic-Chain-Approach, in volleyball athletes with SD.

METHODS

39 professional volleyball athletes were randomly assigned to three groups of 13 each, two experimental, the Mirror-Cross-Education and Kinetic-Chain-Approach, and one control. Both experimental groups performed a Kinetic-Chain-Approach programme, however, the Mirror-Cross-Education group performed the exercise programme with the addition of two mirrors that allowed athletes to observe their opposite non-dyskinetic scapula. Scapular posture asymmetries in cm, the Y-Balance and the Upper-Quarter YBalance after normalizing by limb length the reach distance in each direction, were assessed before and after performing each intervention for 6 weeks.

RESULTS

3x2 two-way Mixed ANOVAs detected significant interactions on scapular posture (p=0.001) on both experimental groups when compared with the control. The Y-Balance and the Upper Quarter Y-Balance scores at both Mirror-Cross-Education and Kinetic-Chain-Approach groups showed significant differences when compared with the control (p<0.05). Overall, variables showed significant superiority of the Mirror-Cross-Education group.

CONCLUSIONS

The Mirror-Cross-Education demonstrated significant effects in scapular posture and in the functional balance tests of volleyball athletes with Scapular Dyskinesis.

Contralateral Strength Training as Preparation for Direct Strength Training in a Patient With Unilateral Foot-Drop Because of Multiple Sclerosis: A Case Report

OBJECTIVE

Direct strength training (DST) is effective in managing unilateral weakness in people with multiple sclerosis (MS). Its feasibility, however, is considerably reduced if one limb is too compromised to train. In this case, contralateral strength training (CST) of the unaffected side to induce a strength transfer to the untrained homologous muscles can help to establish a strength baseline in the weaker limb, eventually allowing direct training. Limited effects for CST, however, have been reported on patient functioning. We tested the effects on dynamometric, electromyographic, and functional outcomes of a sequential combination of CST and DST of the ankle dorsiflexors in a case of MS-related foot-drop.

METHODS

A 56-year-old man diagnosed with relapsing-remitting MS exhibited severe weakness of the right dorsiflexors impairing functional dorsiflexion. The intervention consisted of a 6-week CST of the unaffected dorsiflexors followed by 2 consecutive 6-week DST cycles targeting the weaker dorsiflexors.

RESULTS

At baseline, the participant could not dorsiflex his right ankle but could do so after CST. Maximal strength of the affected dorsiflexors increased by 80% following CST, by 31.1% following DST-1, and by a further 44.6% after DST-2. Neuromuscular recruitment was found progressively increased, with the largest changes occurring after DST-1. Improvements in mobility and walking speed were also detected, although plantar flexors' spasticity on the Modified Ashworth Scale increased from 1+ to 2.

CONCLUSION

In this case, the sequential combination of CST and DST proved a feasible approach to manage severe unilateral weakness in a patient who was not able, at least initially, to dorsiflex his weaker ankle. In this perspective, CST may prime a minimum gain in strength necessary to allow subsequent direct training.

Gait changes following direct versus contralateral strength training: A randomized controlled pilot study in individuals with multiple sclerosis

BACKGROUND

Contralateral strength training (CST) is increasingly investigated and employed as a non-conventional way to induce an indirect gain in strength in the weakened untrained limb. However, its effects on gait performance are more controversial.

RESEARCH QUESTION

To assess and compare the effects of contralateral (CST) and direct (DST) strength training on spatio-temporal parameters, kinematic and kinetic descriptors of gait in persons with relapsing-remitting multiple sclerosis (PwMS).

METHODS

Twenty-eight PwMS (EDSS 2.0-5.5) with inter-side difference in ankle dorsiflexors' strength ≥ 20 % and moderate gait impairment (walking speed 0.70-0.94 m/s), were randomly assigned to a CST (undergoing training of the less-affected dorsiflexors) or DST group (where the most-affected dorsiflexors were trained). Before and after a 6-week high-intensity resistance training (three 25-minute sessions/week), PwMS underwent bilateral measurements of dorsiflexors' maximal strength and assessment of gait spatio-temporal parameters, lower limb joint kinematics and kinetics.

RESULTS AND SIGNIFICANCE

Following the training period, muscle strength increased significantly in both groups (on average, CST + 29.5 %, p < 0.0005; DST + 15.7 %, p = 0.001) with no difference between the two interventions. Significant changes in gait speed (+16.5 %; p < 0.0001) and stride length (+6.0 %; p = 0.04) were detected only after DST, while no difference was detected in the CST group. Ankle moment and ROM were unaffected by the training. In PwMS with mild to moderate disability and lower limb dorsiflexors' strength asymmetry, CST was not inferior to DST in inducing significant strength gains in the untrained most-affected limb. However, only DST significantly improved gait performance and, specifically, walking speed. Even though CST did not worsen asymmetry, data suggest that contralateral approaches should not be recommended straightaway if the training goal is to improve outcomes other than strength and, specifically, walking speed.

The contraction history of the muscle and strength change: lessons learned from unilateral training models

Participation in resistance exercise is encouraged throughout the lifetime, offering such benefits as improved strength and muscle mass accretion. Considerable research has been completed on this topic within the past several decades, with the current narrative dictating that increased muscle size yields further increases in muscle strength. However, there remain unanswered questions relating to the observation that certain training interventions yield only one specific adaptation (strength or size). Studies investigating resistance training often include either bilateral or unilateral exercise programs. Unilateral exercise programs are often used as they allow for comparison between two separate training interventions within the same individual. This is viewed as an advantage, relating to statistical power, but a limitation insofar as one intervention could be confounded by the intervention within the opposing limb. For example, when only one limb is trained both limbs often get stronger (albeit to differing magnitudes), termed the cross-education effect. However, we propose that when both limbs are trained that the cross-education effect may not occur and that the adaptations produced are reflective of the contraction history of the muscle. Herein, we discuss ways to test the idea that strength change may be dictated by the contraction history of the muscle. If each limb responds only to the contraction history within each limb (as opposed to the opposite limb), then this would have immediate ramifications for research design. Furthermore, this would certainly be of importance among injured populations undergoing rehabilitation, seeking to find the most efficacious exercise regimens.

Linking commonly used hand therapy outcome measures to individual areas of the International Classification of Functioning: A systematic review

STUDY DESIGN

Systematic review.

INTRODUCTION

Identifying outcome measures that correspond to the International Classification of Functioning (ICF) provides insight into selecting appropriate outcome tools in hand therapy practice.

PURPOSE OF THE STUDY

The objective of this study is to systematically review patient-reported outcome measures commonly used in hand therapy to determine the extent to which the content represents the biopsychosocial view of the ICF.

METHODS

A comprehensive literature search was conducted. Studies that met inclusion criteria were identified, and outcome measures were extracted. The meaningful concept was determined for each item on the measure and linked to the most specific ICF category. Summary linkage calculations were completed.

RESULTS

Eleven patient-reported outcomes were identified from 43 included studies. Activity and participation had the highest content coverage followed by body functions. There was linking to personal factors and not defined-disability and mental health. Environmental factors were not represented in any of the included outcome measures. The core set representation of unique codes ranged from 8.55% to 18.80% (mean: 11.97%) for the Comprehensive ICF Core Set for Hand Conditions and from 30.43% to 47.83% (mean: 31.40%) for the Brief ICF Core Set for Hand Conditions. The percent representation of the Comprehensive ICF Core Set for Hand Conditions for unique disability ranged from 21.62% to 43.24% (mean: 20.33%) and from 62.50% to 87.50% (mean: 72.22%) for the Brief ICF Core Set for Hand Conditions.

DISCUSSION

None of the included measures represent all categories of the ICF Core Sets for Hand Conditions.

CONCLUSION

Utilizing the most recent refinement rules for the linking process, this study provides comparisons of measures along with clarity of content coverage for the most commonly used tools in the practice of hand therapy.

The validity and reliability of DrGoniometer, a smartphone application, for measuring forearm supination

STUDY DESIGN

Clinical measurement (reliability and validity) study.

INTRODUCTION

Forearm supination is important in many daily activities and is thus measured by therapists and researchers usually with a universal goniometer. DrGoniometer, a SmartPhone application, has been validated for other joint angles in the body.

PURPOSE OF THE STUDY

To establish the reliability and validity of DrGoniometer (CDM S.r.L, Cagliari, Italy) for measuring forearm supination in healthy populations and those with forearm fractures.

METHODS

Participants had sustained a distal radius fracture that was treated non-surgically. Forearm supination of the participant's fractured (n = 30) and healthy forearm (n = 30) was measured using DrGoniometer and the universal goniometer by two assessors. The assessors were blinded to each other's measurements and their own previous measurements. Reliability was established by calculating Intra-class Correlation Coefficients, standard error of measurement and minimal detectable change. The validity of DrGoniometer was established against the universal goniometer using Pearson's correlation co-efficient.

RESULTS

Intra-rater reliability of both DrGoniometer and the universal goniometer was high for both fractured and healthy forearms (ICCs ranged from 0.74-0.88). Inter-rater reliability of both DrGoniometer and the universal goniometer was also high in the fractured forearm group (0.76 and 0.72 respectively), but low in the healthy forearm group (0.34 and 0.42 respectively). Correlation between the tools was excellent across the fractured and healthy forearm groups (0.94 and 0.93 respectively).

DISCUSSION

Both goniometers demonstrated good-to-excellent intrarater and iner-rater reliability except in the healthy forearm group where both goniometers demonstrated poor inter-rater reliability which could be due to assessor instructions. The speed the photo can be taken and the digital record obtained are valuable aspects of DrGoniometer.

CONCLUSION

DrGoniometer is a valid, alternate tool for measuring forearm supination.

Changes in fall risk and functional status in women aged 50 years and older after distal radius fracture: A prospective 1-year follow-up study

STUDY DESIGN

Prospective cohort study.

INTRODUCTION

Few studies have evaluated the course of recovery after distal radius fracture (DRF) when functional decline and fracture risk may be affected.

PURPOSE OF THE STUDY

The purpose of this study was to determine changes in overall functional status over the first year after a DRF in women aged 50 years and older.

METHODS

Seventy-eight women were assessed for balance, balance confidence, lower extremity strength, gait speed, fall history, physical activity levels, and self-reported wrist pain and function (Patient-Rated Wrist Evaluation) at weeks 1, 3, 9, 12, 26, and 52 after DRF. Descriptive data were generated for all variables; a 3-way mixed analysis of variance with repeated measures was used to compare differences between participants aged 50-65 years and 65 years and older.

RESULTS

There was a significant improvement in functional status measures for both age categories except single-leg balance and fast gait speed, from 1 week after fracture extending up to 1 year after fracture (ranging from 6.1% improvement to 25% improvement, P < .05). There was no significant time × age interaction, as both age groups had the same pattern of recovery; however, there was significantly lower functional status in the older group across all time points.

CONCLUSION

Regardless of age, monitoring and addressing functional status including upper limb function, overall strength, balance, confidence, usual gait speed, and physical activity right up to 1 year after fracture is an important consideration for clinicians treating women recovering from DRF. Given the high future fracture risk for these women, identifying functional recovery patterns can help to direct future research and determine preventative strategies.

Unilateral dorsiflexor strengthening with mirror therapy to improve motor function after stroke: A pilot randomized study

BACKGROUND

Independently, cross-education, the performance improvement of the untrained limb following unilateral training, and mirror therapy have shown to improve lower limb functioning poststroke. Mirror therapy has shown to augment the cross-education effect in healthy populations. However, this concept has not yet been explored in a clinical setting.

OBJECTIVES

This study set out to investigate the feasibility and potential efficacy of applying cross-education combined with mirror therapy compared with cross-education alone for lower limb recovery poststroke.

METHODS

Thirty-one chronic stroke participants (age 61.7 ± 13.3) completed either a unilateral strength training (ST; n = 15) or unilateral strength training with mirror-therapy (MST; n = 16) intervention. Both groups isometrically strength trained the less-affected ankle dorsiflexors three times per week for 4 weeks. Only the MST group observed the mirror reflection of the training limb. Patient eligibility, compliance, treatment reliability, and outcome measures were assessed for feasibility. Maximal voluntary contraction (MVC; peak torque, rate of torque development, and average torque), 10-m walk test, timed up and go (TUG), Modified Ashworth Scale (MAS), and the London Handicap Scale (LHS) were assessed at pretraining and posttraining.

RESULTS

Treatment and assessments were well tolerated without adverse effects. No between group differences were identified for improvement in MVC, MAS, TUG, or LHS. Only the combined treatment was associated with functional improvements with the MST group showing an increase in walking velocity.

CONCLUSION

Cross-education plus mirror therapy may have potential for improving motor function after stroke. This study demonstrates the feasibility of the combination treatment and the need for future studies with larger sample sizes to investigate the effectiveness of the treatment.

The time course of cross-education during short-term isometric strength training

PURPOSE

This study examined the time course of contralateral adaptations in maximal isometric strength (MVC), rate of force development (RFD), and rate of electromyographic (EMG) rise (RER) during 4 weeks of unilateral isometric strength training with the non-dominant elbow flexors.

METHODS

Twenty participants were allocated to strength training (n = 10, three female, two left hand dominant) or control (n = 10, three female, two left hand dominant) groups. Both groups completed testing at baseline and following each week of training to evaluate MVC strength, EMG amplitude, RFD and RER at early (RFD₅₀, RER₅₀) and late (RFD₂₀₀, RER₂₀₀) contraction phases for the dominant 'untrained' elbow flexors. The training group completed 11 unilateral isometric training sessions across 4 weeks.

RESULTS

The contralateral improvements for MVC strength (P < 0.01) and RFD₂₀₀ (P = 0.017) were evidenced after 2 weeks, whereas RFD₅₀ (P < 0.01) and RER₅₀ (P = 0.02) showed significant improvements after 3 weeks. Each of the dependent variables was significantly (P < 0.05) greater than baseline values at the end of the training intervention for the trained arm. No changes in any of the variables were observed for the control group (P > 0.10).

CONCLUSIONS

Unilateral isometric strength training for 2-3 weeks can produce substantial increases in isometric muscle strength and RFD for both the trained and untrained arms. These data have implications for rehabilitative exercise design and prescription.

Cross-education does not improve early and late-phase rehabilitation outcomes after ACL reconstruction: a randomized controlled clinical trial

PURPOSE

Limited evidence suggests that cross-education affords clinical benefits in the initial 8 weeks after anterior cruciate ligament (ACL) reconstruction, but it is unknown if such cross-education effects are reproducible and still present in later phases of rehabilitation. We examined whether cross-education, as an adjuvant to standard therapy, would accelerate the rehabilitation up to 26 weeks after ACL reconstruction by attenuating quadriceps weakness.

METHODS

ACL-reconstructed patients were randomized into experimental (n = 22) and control groups (n = 21). Both groups received standard care after ACL reconstruction. In addition, the experimental group strength trained the quadriceps of the non-operated leg during weeks 1-12 after surgery (i.e., cross-education). Self-reported knee function was assessed with the Hughston Clinic Knee score as the primary outcome. Secondary outcomes were maximal quadriceps and hamstring strength and single leg hop distance. All outcomes were measured 29 ± 23 days prior to surgery, as a reference, and at 5-week, 12-week, and 26-week post-surgery.

RESULTS

Both groups scored 12% worse on self-reported knee function 5-week post-surgery (95% CI 7-17) and showed 15% improvement 26-week post-surgery (95% CI - 20 to - 10). No cross-education effect was found. Interestingly, males scored 8-10% worse than females at each time point post-surgery. None of 33 secondary outcomes showed a cross-education effect. At 26-week post-surgery, both legs improved maximal quadriceps (5-14%) and hamstring strength (7-18%), and the non-injured leg improved 2% in hop distance. The ACL recovery was not affected by limb dominance and age.

CONCLUSION

26 weeks of standard care improved self-reported knee function and maximal leg strength relative to pre-surgery and adding cross-education did not further accelerate ACL recovery.

LEVEL OF EVIDENCE

I.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION

This randomized controlled clinical trial is registered at the Dutch trial register ( http://www.trialregister.nl ) under NTR4395.

Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength

Cross-education describes the strength gain in the opposite, untrained limb following a unilateral strength training program. Since its discovery in 1894, several studies now confirm the existence of cross-education in contexts that involve voluntary dynamic contractions, eccentric contraction, electrical stimulation, whole-body vibration and, more recently, following mirror feedback training. Although many aspects of cross-education have been established, the mediating neural mechanisms remain unclear. Overall, the findings of this review show that the neural adaptations to cross-education of muscle strength most likely represent a continuum of change within the central nervous system that involves both structural and functional changes within cortical motor and non-motor regions. Such changes are likely to be the result of more subtle changes along the entire neuroaxis which include, increased corticospinal excitability, reduced cortical inhibition, reduced interhemispheric inhibition, changes in voluntary activation and new regions of cortical activation. However, there is a need to widen the breadth of research by employing several neurophysiological techniques (together) to better understand the potential mechanisms mediating cross-education. This fundamental step is required in order to better prescribe targeted and effective guidelines for the clinical practice of cross-education. There is a need to determine whether similar cortical responses also occur in clinical populations where, perhaps, the benefits of cross-education could be best observed.

Cross-education does not accelerate the rehabilitation of neuromuscular functions after ACL reconstruction: a randomized controlled clinical trial

PURPOSE

Cross-education reduces quadriceps weakness 8 weeks after anterior cruciate ligament (ACL) surgery, but the long-term effects are unknown. We investigated whether cross-education, as an adjuvant to the standard rehabilitation, would accelerate recovery of quadriceps strength and neuromuscular function up to 26 weeks post-surgery.

METHODS

Group allocation was randomized. The experimental (n = 22) and control (n = 21) group received standard rehabilitation. In addition, the experimental group strength trained the quadriceps of the non-injured leg in weeks 1-12 post-surgery (i.e., cross-education). Primary and secondary outcomes were measured in both legs 29 ± 23 days prior to surgery and at 5, 12, and 26 weeks post-surgery.

RESULTS

The primary outcome showed time and cross-education effects. Maximal quadriceps strength in the reconstructed leg decreased 35% and 12% at, respectively, 5 and 12 weeks post-surgery and improved 11% at 26 weeks post-surgery, where strength of the non-injured leg showed a gradual increase post-surgery up to 14% (all p ≤ 0.015). Limb symmetry deteriorated 9-10% more for the experimental than control group at 5 and 12 weeks post-surgery (both p ≤ 0.030). One of 34 secondary outcomes revealed a cross-education effect: Voluntary quadriceps activation of the reconstructed leg was 6% reduced for the experimental vs. control group at 12 weeks post-surgery (p = 0.023). Both legs improved force control (22-34%) and dynamic balance (6-7%) at 26 weeks post-surgery (all p ≤ 0.043). Knee joint proprioception and static balance remained unchanged.

CONCLUSION

Standard rehabilitation improved maximal quadriceps strength, force control, and dynamic balance in both legs relative to pre-surgery but adding cross-education did not accelerate recovery following ACL reconstruction.

Contralateral effects of unilateral training: sparing of muscle strength and size after immobilization

The contralateral effects of unilateral strength training, known as cross-education of strength, date back well over a century. In the last decade, a limited number of studies have emerged demonstrating the preservation or "sparing" effects of cross-education during immobilization. Recently published evidence reveals that the sparing effects of cross-education show muscle site specificity and involve preservation of muscle cross-sectional area. The new research also demonstrates utility of training with eccentric contractions as a potent stimulus to preserve immobilized limb strength across multiple modes of contraction. The cumulative data in nonclinical settings suggest that cross-education can completely abolish expected declines in strength and muscle size in the range of ∼13% and ∼4%, respectively, after 3-4 weeks of immobilization of a healthy arm. The evidence hints towards the possibility that unique mechanisms may be involved in preservation effects of cross-education, as compared with those that lead to functional improvements under normal conditions. Cross-education effects after strength training appear to be larger in clinical settings, but there is still only 1 randomized clinical trial demonstrating the potential utility of cross-education in addition to standard treatment. More work is necessary in both controlled and clinical settings to understand the potential interaction of neural and muscle adaptations involved in the observed sparing effects, but there is growing evidence to advocate for the clinical utility of cross-education.

Unilateral strength training leads to muscle-specific sparing effects during opposite homologous limb immobilization

Cross education (CE) occurs after unilateral training whereby performance of the untrained contralateral limb is enhanced. A few studies have shown that CE can preserve or "spare" strength and size of an opposite immobilized limb, but the specificity (i.e., trained homologous muscle and contraction type) of these effects is unknown. The purpose was to investigate specificity of CE "sparing" effects with immobilization. The nondominant forearm of 16 participants was immobilized with a cast, and participants were randomly assigned to a resistance training (eccentric wrist flexion, 3 times/week) or control group for 4 weeks. Pre- and posttesting involved wrist flexors and extensors eccentric, concentric and isometric maximal voluntary contractions (via dynamometer), muscle thickness (via ultrasound), and forearm muscle cross-sectional area (MCSA; via peripheral quantitative computed tomography). Only the training group showed strength preservation across all contractions in the wrist flexors of the immobilized limb (training: -2.4% vs. control: -21.6%; P = 0.04), and increased wrist flexors strength of the nonimmobilized limb (training: 30.8% vs. control: -7.4%; P = 0.04). Immobilized arm MCSA was preserved for the training group only (training: 1.3% vs. control: -2.3%; P = 0.01). Muscle thickness differed between groups for the immobilized (training: 2.8% vs. control: -3.2%; P = 0.01) and nonimmobilized wrist flexors (training: 7.1% vs. control: -3.7%; P = 0.02). Strength preservation was nonspecific to contraction type ( P = 0.69, [Formula: see text] = 0.03) yet specific to the trained flexors muscle. These findings suggest that eccentric training of the nonimmobilized limb can preserve size of the immobilized contralateral homologous muscle and strength across multiple contraction types. NEW & NOTEWORTHY Unilateral strength training preserves strength, muscle thickness, and muscle cross-sectional area in an opposite immobilized limb. The preservation of size and strength was confined to the trained homologous muscle group. However, strength was preserved across multiple contraction types.

Does Fall Arrest Strategy Training Added to a Fall Prevention Programme Improve Balance, Strength, and Agility in Older Women? A Pilot Study

Purpose: The purpose of this study was to determine the effect of a unique exercise programme (Fall Arrest Strategy Training, or FAST) on upper body strength, range of motion (ROM), and fall risk in older women. FAST was designed to improve upper body capacity to prevent injury when a fall cannot be avoided. Method: A quasi-randomized site design included 71 older women (aged 67-95 y, mean age 83 years), who participated either in a standard fall prevention programme (Staying on Your Feet, or SOYF; n=29) or in SOYF combined with FAST (n=42). The women were measured three times-at baseline, after the 12-week intervention, and again 12 weeks later-for upper body strength, ROM, and fall risk factors (fall risk questionnaire, balance, mobility, and leg strength). Results: No significant differences were found in age, physical activity, or cognitive or functional status between the SOYF-standard and the SOYF-FAST groups. Both groups improved their fall risk status after the intervention, with no significant differences between them; however, the SOYF-FAST group showed greater improvements in upper extremity strength and ROM (p=0.007). Conclusion: FAST can feasibly be integrated into fall prevention programming, with additional gains in upper body strength and ROM in older women.

Prescribed exercise programs may not be effective in reducing impairments and improving activity during upper limb fracture rehabilitation: a systematic review

QUESTION

What is the effect of exercise on increasing participation and activity levels and reducing impairment in the rehabilitation of people with upper limb fractures?

DESIGN

Systematic review of controlled trials.

PARTICIPANTS

Adults following an upper limb fracture.

INTERVENTION

Any exercise therapy program, including trials where exercise was delivered to both groups provided that the groups received different amounts of exercise.

OUTCOME MEASURES

Impairments of body structure and function, activity limitations and participation restrictions.

RESULTS

Twenty-two trials were identified that evaluated 1299 participants with an upper limb fracture. There was insufficient evidence from 13 trials to support or refute the effectiveness of home exercise therapy compared with therapist-supervised exercise or therapy that included exercise following distal radius or proximal humeral fractures. There was insufficient evidence from three trials to support or refute the effectiveness of exercise therapy compared with advice/no exercise intervention following distal radius fracture. There was moderate evidence from five trials (one examining distal radius fracture, one radial head fracture, and three proximal humeral fracture) to support commencing exercise early and reducing immobilisation in improving activity during upper limb rehabilitation compared with delayed exercise and mobilisation. There was preliminary evidence from one trial that exercise to the non-injured arm during immobilisation might lead to short-term benefits on increasing grip strength and range of movement following distal radius fracture. Less than 40% of included trials reported adequate exercise program descriptions to allow replication according to the TIDieR checklist.

CONCLUSION

There is emerging evidence that current prescribed exercise regimens may not be effective in reducing impairments and improving activity following an upper limb fracture. Starting exercise early combined with a shorter immobilisation period is more effective than starting exercise after a longer immobilisation period.

REGISTRATION

CRD42016041818. [Bruder AM, Shields N, Dodd KJ, Taylor NF (2017) Prescribed exercise programs may not be effective in reducing impairments and improving activity during upper limb fracture rehabilitation: a systematic review. Journal of Physiotherapy 63: 205-220].

Efecto de las intervenciones fisioterapéuticas en personas con fractura distal de radio

Introducción. La fractura distal de radio (FDR) es muy frecuente y afecta a todos los grupos poblacionales.Objetivo. Realizar una revisión sistemática de la mejor evidencia disponible para determinar el efecto de las intervenciones fisioterapéuticas sobre el dolor, el rango de movimiento, la fuerza muscular y la funcionalidad en personas con fractura distal de radio.Materiales y métodos. Se realizó una búsqueda sistemática de ensayos clínicos controlados en las bases de datos ScienceDirect, PubMed, Medline y Embase.Resultados. Se encontraron 14 estudios que cumplieron los criterios de selección.Conclusión. La evidencia sugiere que intervenciones terapéuticas supervisadas que incluyan modalidades físicas y del ejercicio con una duración entre 6 y 9 semanas, con un promedio de 18 sesiones y realizadas tres veces a la semana mejoran de forma significativa las variables estudiadas en pacientes con FDR. Es necesario que futuros estudios establezcan la relación dosis-respuesta de estas intervenciones.

Cross-education of muscular strength following unilateral resistance training: a meta-analysis

PURPOSE

Cross-education (CE) of strength is a well-known phenomenon whereby exercise of one limb can induce strength gains in the contralateral untrained limb. The only available meta-analyses on CE, which date back to a decade ago, estimated a modest 7.8% increase in contralateral strength following unilateral training. However, in recent years new evidences have outlined larger contralateral gains, which deserve to be systematically evaluated. Therefore, the aim of this meta-analysis was to appraise current data on CE and determine its overall magnitude of effect.

METHODS

Five databases were searched from inception to December 2016. All randomized controlled trials focusing on unilateral resistance training were carefully checked by two reviewers who also assessed the eligibility of the identified trials and extracted data independently. The risk of bias was assessed using the Cochrane Risk-of-Bias tool.

RESULTS

Thirty-one studies entered the meta-analysis. Data from 785 subjects were pooled and subgroup analyses by body region (upper/lower limb) and type of training (isometric/concentric/eccentric/isotonic-dynamic) were performed. The pooled estimate of CE was a significant 11.9% contralateral increase (95% CI 9.1-14.8; p < 0.00001; upper limb: + 9.4%, p < 0.00001; lower limb: + 16.4%, p < 0.00001). Significant CE effects were induced by isometric (8.2%; p = 0.0003), concentric (11.3%; p < 0.00001), eccentric (17.7%; p = 0.003) and isotonic-dynamic training (15.9%; p < 0.00001), although a high risk of bias was detected across the studies.

CONCLUSIONS

Unilateral resistance training induces significant contraction type-dependent gains in the contralateral untrained limb. Methodological issues in the included studies are outlined to provide guidance for a reliable quantification of CE in future studies.

Ipsilateral corticomotor responses are confined to the homologous muscle following cross-education of muscular strength

Cross-education of strength occurs when strength-training 1 limb increases the strength of the untrained limb and is restricted to the untrained homologous muscle. Cortical circuits located ipsilateral to the trained limb might be involved. We used transcranial magnetic stimulation (TMS) to determine the corticomotor responses from the untrained homologous (biceps brachii) and nonhomologous (flexor carpi radialis) muscle following strength-training of the right elbow flexors. Motor evoked potentials were recorded from the untrained left biceps brachii and flexor carpi radialis during a submaximal contraction from 20 individuals (10 women, 10 men; aged 18-35 years; training group, n = 10; control group, n = 10) before and after 3 weeks of strength-training the right biceps brachii at 80% of 1-repetition maximum. Recruitment-curves for corticomotor excitability and inhibition of the untrained homologous and nonhomologous muscle were constructed and assessed by examining the area under the recruitment curve. Strength-training increased strength of the trained elbow flexors (29%), resulting in an 18% increase in contralateral strength of the untrained elbow flexors (P < 0.0001). The trained wrist flexors increased by 19%, resulting in a 12% increase in strength of the untrained wrist flexors (P = 0.005). TMS showed increased corticomotor excitability and decreased corticomotor inhibition for the untrained homologous muscle (P < 0.05); however, there were no changes in the untrained nonhomologous muscle (P > 0.05). These findings show that the cross-education of muscular strength is spatially distributed; however, the neural adaptations are confined to the motor pathway ipsilateral to the untrained homologous agonist.

Cross-Activation of the Motor Cortex during Unilateral Contractions of the Quadriceps

Transcranial magnetic stimulation (TMS) studies have demonstrated that unilateral muscle contractions in the upper limb produce motor cortical activity in both the contralateral and ipsilateral motor cortices. The increase in excitability of the corticomotor pathway activating the resting limb has been termed “cross-activation”, and is of importance due to its involvement in cross-education and rehabilitation. To date, very few studies have investigated cross-activation in the lower limb. Sixteen healthy participants (mean age 29 ± 9 years) took part in this study. To determine the effect of varying contraction intensities in the lower limb, we investigated corticomotor excitability and intracortical inhibition of the right rectus femoris (RF) while the left leg performed isometric extension at 0%, 25%, 50%, 75% and 100% of maximum force output. Contraction intensities of 50% maximal force output and greater produced significant cross-activation of the corticomotor pathway. A reduction in silent period duration was observed during 75% and 100% contractions, while the release of short-interval intracortical inhibition (SICI) was only observed during maximal (100%) contractions. We conclude that increasing isometric contraction intensities produce a monotonic increase in cross-activation, which was greatest during 100% force output. Unilateral training programs designed to induce cross-education of strength in the lower limb should therefore be prescribed at the maximal intensity tolerable.

Effectiveness of Occupational Therapy Interventions for Adults With Musculoskeletal Conditions of the Forearm, Wrist, and Hand: A Systematic Review

Occupational therapy practitioners are key health care providers for people with musculoskeletal disorders of the distal upper extremity. It is imperative that practitioners understand the most effective and efficient means for remediating impairments and supporting clients in progressing to independence in purposeful occupations. This systematic review provides an update to a previous review by summarizing articles published between 2006 and July 2014 related to the focused question, What is the evidence for the effect of occupational therapy interventions on functional outcomes for adults with musculoskeletal disorders of the forearm, wrist, and hand? A total of 59 articles were reviewed. Evidence for interventions was synthesized by condition within bone, joint, and general hand disorders; peripheral nerve disorders; and tendon disorders. The strongest evidence supports postsurgical early active motion protocols and splinting for various conditions. Very few studies have examined occupation-based interventions. Implications for occupational therapy practice and research are provided.

Cross-education after high-frequency versus low-frequency volume-matched handgrip training

INTRODUCTION

Cross-education training programs cause interlimb asymmetry of strength and hypertrophy. We examined the cross-education effects from a high-frequency (HF) versus a low-frequency (LF) volume-matched handgrip training program on interlimb asymmetry.

METHODS

Right-handed participants completed either HF (n = 10; 2 × 6 repetitions 10 times per week) or LF (n = 9; 5 × 8 repetitions 3 times per week) training. Testing occurred twice before and once after 4 weeks of right-handed isometric handgrip training totaling 120 weekly repetitions. Measures were maximal isometric handgrip and wrist flexion torque, muscle thickness, and muscle activation (electromyography; EMG).

RESULTS

Grip strength was greater in both limbs posttraining, pooled across groups (P < 0.001). Trained limb muscle thickness increased in both groups (P < 0.05; untrained, P = 0.897). EMG and wrist flexion torque did not change (all P > 0.103).

DISCUSSION

Both LF and HF induced cross-education of grip strength to the untrained limb, but HF did not reduce asymmetry. These findings have implications for injury rehabilitation. Muscle Nerve 56: 689-695, 2017.