Lower extremity work along with triceps surae structure and activation is altered with jumping after Achilles tendon repair

Achilles Tendon Surgical Repair Partially Restores Early Plantar Flexor Structure and Function in a Rat Model

Achilles tendon ruptures significantly impair long-term patient function, with two-thirds of patients experiencing persistent functional deficits. Although nonsurgical treatment has gained popularity due to its perceived lower risk of complications, the specific effects of this approach on tendon healing, muscle function, and overall performance remain poorly understood. Directly comparing surgical and nonsurgical treatment options in a clinical population is challenging given the diverse nature of the patient population. Preclinical models are essential to isolate the mechanisms underlying these treatments, enabling a detailed examination of the structural and functional outcomes that are difficult to assess in human studies. Here, we surgically induced Achilles tendon ruptures in 20 adult male Sprague Dawley rats and repaired the rupture in half of these animals. Then, functional outcomes were assessed by measuring plantar flexor torque across the ankle's range of motion using a custom-developed small animal dynamometer, and structural changes were evaluated through measurements of Achilles tendon elongation and plantar flexor muscle mass. We found that surgical treatment led to 11%-35% increased functional plantar flexor torque outcomes compared to nonsurgical treatment. Additionally, plantar flexor muscle mass decreased by 21% in nonsurgically treated animals compared to only 12% in the surgically treated group. Our results suggest that surgically repairing a tendon rupture restores plantar flexor function more effectively than nonsurgical treatment; however, persistent functional deficits in both groups indicate that enhanced rehabilitation strategies are necessary for full functional restoration.

Rehabilitation and Return to Sports after Achilles Tendon Repair

Rehabilitation protocols post-Achilles tendon repair vary widely, particularly regarding weight bearing (WB) and immobilization duration, impacting recovery trajectories significantly. This commentary focuses on rehabilitation strategies following acute Achilles tendon repair (ATR), emphasizing early mobilization and progressive loading. Techniques such as blood flow restriction training (BFRT) and progressive loading to restore strength and tendon mechanical properties are discussed in the context of optimizing recovery, minimizing tendon elongation and facilitating safe return to sport (RTS). This manuscript highlights current evidence and clinical insights to guide practitioners in optimizing rehabilitation protocols for athletes recovering from ATR, aiming to improve functional outcomes and support safe return to athletic activity.

Does Radial Extracorporeal Shockwave Therapy Applied to the Achilles Tendon Influence Ankle Functionality?

This study aimed to determine the effectiveness of radial extracorporeal shockwave therapy (rESWT) in enhancing ankle function in patients with Achilles tendon injuries. The choice of rESWT was based on previous success in the treatment of musculoskeletal conditions. The study involved an intervention group that received rESWT, and a control group that received sham therapy. The results revealed that rESWT led to significant improvements in single-leg vertical jump (d = 0.55, p < 0.05), indicating enhanced power generation and ankle functionality that were not observed in the control group. Additionally, the therapy resulted in increased ankle mobility, as observed by improvements in plantar flexion and heel-rise tests. Interestingly, these functional gains were not accompanied by changes in the Achilles tendon stiffness, suggesting that the benefits of rESWT may be more functional than structural. This study highlights rESWT as a promising tool for rehabilitation, particularly following Achilles tendon injuries. The study concluded that, although rESWT appears to improve certain aspects of ankle function, further studies with a larger and more diverse population over a longer period are necessary to confirm these findings and establish comprehensive treatment protocols.

Case study: The influence of Achilles tendon rupture on knee joint stress during counter-movement jump - Combining musculoskeletal modeling and finite element analysis

BACKGROUND

Presently, the current research concerning Achilles tendon rupture repair (ATR) is predominantly centered on the ankle joint, with a paucity of evidence regarding its impact on the knee joint. ATR has the potential to significantly impede athletic performance and increase tibiofemoral contact forces in athletes. The purpose of this study was to prognosticate the distribution of stress within the knee joint during a countermovement jump through the use of a simulation method that amalgamated a musculoskeletal model of a patient who underwent Achilles tendon rupture repair with a finite element model of the knee joint.

METHODS

A male elite badminton player who had suffered an acute Achilles tendon rupture in his right leg one year prior was selected as our study subject. In order to analyze his biomechanical data, we employed both the OpenSim musculoskeletal model and finite element model to compute various parameters such as joint angles, joint moments, joint contact forces, and the distribution of knee joint stress.

RESULTS

During the jumping phase, a significantly lower knee extension angle (p < 0.001), ankle dorsiflexion angle (p = 0.002), peak vertical ground reaction force (p < 0.001), and peak tibiofemoral contact force (p = 0.009) were observed on the injured side than on the uninjured side. During the landing phase, the ankle range of motion (ROM) was significantly lower on the injured side than on the uninjured side (p = 0.009), and higher peak vertical ground reaction forces were observed (p = 0.012). Additionally, it is logical that an injured person will put higher load on the uninjured limb, but the finite element analysis indicated that the stresses on the injured side of medial meniscus and medial cartilage were significantly greater than the uninjured side.

CONCLUSIONS

An Achilles tendon rupture can limit ankle range of motion and lead to greater joint stress on the affected area during countermovement jumps, especially during the landing phase. This increased joint stress may also transfer more stress to the soft tissues of the medial knee, thereby increasing the risk of knee injury. It is worth noting that this study only involves the average knee flexion angle and load after ATR in one athlete. Caution should be exercised when applying the conclusions, and in the future, more participants should be recruited to establish personalized knee finite element models to validate the results.

Altered Ankle Muscle Activation at 2-Year Post Achilles Tendon Repair: An Age, Gender, and Activity Level-Matched Comparison With Healthy Subjects

CONTEXT

The study purpose was to compare the ankle muscle activation and dynamic ankle joint stability of subjects who underwent endoscopy-assisted Achilles tendon repair (ATR; at ≥ 2 y postsurgery) with age, gender, and activity level-matched healthy control group subjects.

DESIGN

Prospective, cross-sectional study. All functional tests were performed on the involved ankle of the ATR group, and at the matched side of healthy age, gender, and activity-level control group subjects.

METHODS

Fifteen men in each group were evaluated for medial and lateral gastrocnemius, soleus, tibialis anterior, and peroneus longus muscle activation during modified star excursion balance test and heel-rise test performance. The weight-bearing lunge test (ankle dorsiflexion) and heel-rise test distance (ankle plantar flexion) also determined weight-bearing, active ankle mobility magnitudes. The Achilles Tendon Total Rupture Score and Foot and Ankle Outcome Score provided patient-reported outcome perceptions specific to Achilles tendon rupture and comprehensive foot and ankle symptoms and function, respectively.

RESULTS

Medial (P = .005) and lateral (P = .012) gastrocnemius displayed greater activation amplitudes in the ATR group during the star excursion balance test, and peroneus longus displayed greater activation amplitudes during the heel-rise test (P = .006). The star excursion balance test reach distance was comparable between groups. Active weight-bearing ankle plantar flexion (heel-rise test) and dorsiflexion (weight-bearing lunge test) mobility magnitudes were lower in the ATR group.

CONCLUSIONS

Subjects who underwent endoscopy-assisted percutaneous ATR had reduced active weight-bearing ankle dorsiflexion and plantar flexion mobility magnitudes and greater gastrocnemius and peroneus longus neuromuscular activation when performing the same tasks as healthy control group subjects. As surgical approaches evolve to less invasive, soft tissue preserving methods with less tissue morbidity and faster healing, rehabilitation approaches may likewise need to evolve.

LEVEL OF EVIDENCE

Level III.

Distal overactivation of gastrocnemius medialis in persistent plantarflexion weakness following Achilles tendon repair

Structural alterations of the triceps surae and Achilles tendon (AT) can promote plantarflexion weakness one-year following an AT repair, influencing the activation strategies of the Gastrocnemius Medialis (GM) muscle. However, this is yet to be demonstrated. We aimed to determine whether patients with plantar flexion weakness one-year after AT repair show altered GM spatial activation. In this cross-sectional and case-control study, ten middle-aged men (age 34 ± 7 years old, and 12.9 ± 1.1 months post-surgery) with a high AT total rupture score who attended conventional physiotherapy for six months after surgery, and ten healthy control men (age 28 ± 9 years old), performed maximal and submaximal (40, 60 and 90%) voluntary isometric plantarflexion contractions on a dynamometer. The peak plantar flexor torque was determined by isokinetic dynamometry and the GM neuromuscular activation was measured with a linear surface-electromyography (EMG) array. Overall EMG activation (averaged channels) increased when the muscle contraction levels increased for both groups. EMG spatial analysis in AT repaired group showed an increased activation located distally at 85-99%, 75-97%, and 79-97% of the electrode array length for 40%, 60%, and 90% of the maximal voluntary isometric contractions, respectively. In conclusion, patients with persistent plantar flexion weakness after AT rupture showed higher distal overactivation in GM.

Are Prospective Criteria or Objective Clinical Measures Utilized in Return to Play (RTP) Decision Making After Ankle Surgery? A Scoping Review

Background

Manuscripts discussing return to play (RTP) following ankle surgery are common. However, the definition for RTP and the method by which it is determined remains unclear. The purpose of this scoping review was to clarify how RTP is defined following ankle surgery in physically active patients, to identify key factors informing RTP decision making (such as objective clinical measures), and make recommendations for future research.

Methods

A scoping literature review was performed in April 2021 using PubMed, EMBASE, and Nursing and Allied Health databases. Thirty studies met inclusion criteria: original research following ankle surgery reporting at least 1 objective clinical test and documentation of RTP. Data were extracted for study methods and outcomes (RTP definition, RTP outcomes, and objective clinical tests).

Results

The scoping review found studies on 5 ankle pathologies: Achilles tendon rupture, chronic lateral ankle instability, anterior ankle impingement, peroneal tendon dislocation, and ankle fracture. RTP criteria were not provided in the majority of studies (18/30 studies). In the studies that provided them, the RTP criteria were primarily based on time postsurgery (8/12) rather than validated criteria. Objective clinical outcome measures and patient-reported outcome measures (PROMs) were documented for each surgery when available. Both clinical outcomes and PROMs were typically measured >1 year postsurgery.

Conclusion

In physically active patients who have had ankle surgery, RTP remains largely undefined and is not consistently based on prospective objective criteria nor PROMS. We recommend standardization of RTP terminology, adoption of prospective criteria for both clinical measures and PROMs to guide RTP decision making, and enhanced reporting of patient data at the time of RTP to develop normative values and determine when the decision to RTP is not safe.

Level of Evidence

Level IV, scoping review.

Comparable Recovery and Compensatory Strategies in Heel-Rise Performance After a Surgically Repaired Acute Achilles Tendon Rupture: An In Vivo Kinematic Analysis Comparing Early Functional Mobilization and Standard Treatment

BACKGROUND

Deficits in calf muscle function and heel-rise performance are common after an Achilles tendon rupture (ATR) and are related to tendon elongation and calf muscle atrophy. Whether early functional mobilization (EFM) can improve calf muscle function compared with standard treatment (ST) with 2 weeks of immobilization and unloading in a plaster cast is unknown.

HYPOTHESIS

EFM would lead to superior recovery of heel-rise performance, as demonstrated by more symmetrical side-to-side ankle and knee joint kinematics, compared with ST.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

In total, 47 patients with an ATR were prospectively included and treated with open surgical repair and randomized 2:1 postoperatively to either EFM or ST. Overall, 29 patients were treated with a dynamic orthosis (EFM), and 18 underwent ST. At 8 weeks and 6 months after ATR repair, 3-dimensional motion analysis of heel-rise performance was conducted. At 6 months, tendon length and muscle volume were assessed with ultrasound imaging, calf muscle function with the heel-rise test, and patient-reported outcomes with the Achilles tendon Total Rupture Score.

RESULTS

At 8 weeks and 6 months, there were no significant group differences between the EFM and ST groups in heel-rise performance, but significant side-to-side differences in ankle and knee kinematics were detected. At 8 weeks and 6 months, both the EFM and ST groups showed a significantly decreased peak ankle plantarflexion angle and increased knee flexion angle on the injured limb compared with the uninjured limb during bilateral heel raises. Linear regression demonstrated that greater atrophy of the medial gastrocnemius muscle (P = .008) and higher body weight (P < .001) were predictors of a decreased maximum peak ankle plantarflexion angle on the injured limb at 6 months.

CONCLUSION

EFM after an ATR repair did not lead to superior recovery of calf muscle function, as assessed by heel-rise performance, compared with ST. Increased knee flexion seemed to be a compensatory strategy for decreased ankle plantarflexion. Medial gastrocnemius atrophy and increased body weight were additional factors associated with a decreased ankle plantarflexion angle.

REGISTRATION

NCT02318472 (ClinicalTrials.gov identifier).

No effects of early functional mobilization on gait patterns after acute Achilles tendon rupture repair

This study aimed to compare recovery of gait patterns in patients treated with early functional mobilization (EFM) or standard treatment (ST) after Achilles tendon rupture repair. Second, this study aimed to explore associations between gait patterns and tendon elongation and calf muscle atrophy, respectively. Forty-seven patients (12 females), mean age 38.7 (7.3) years, were included. Patients were postoperatively randomized to EFM (n = 29), including immediate weightbearing and ankle motion for 6 weeks, or ST (n = 18), with 2 weeks of unloading in a plaster cast followed by 4 weeks of weightbearing in an orthosis. Three-dimensional gait analyses were performed at 8 weeks and 6 months postoperatively to evaluate ankle and knee kinematics and kinetics. Ultrasound imaging was performed to assess tendon length and calf muscle atrophy. At 8 weeks, there were no significant group differences in ankle and knee kinematics and kinetics, while side-to-side differences between injured and uninjured side were present within both groups. At 6 months, the ST group exhibited higher generating ankle power and greater peak moments in ankle and knee compared to the EFM group. In both groups, peak ankle dorsiflexion angle was greater on the injured side compared to the uninjured side. No correlations were found between ankle joint gait deviations and degree of tendon elongation or muscle atrophy. Clinical significance: The accelerated rehabilitation regimen with EFM did not result in a more symmetrical gait pattern. The gait pattern deviations in the ankle joint were not related to the degree of muscle atrophy or tendon elongation.

Effect of Heel Lift Insoles on Lower Extremity Muscle Activation and Joint Work during Barbell Squats

The effect of heel elevation on the barbell squat remains controversial, and further exploration of muscle activity might help find additional evidence. Therefore, 20 healthy adult participants (10 males and 10 females) were recruited for this study to analyze the effects of heel height on lower extremity kinematics, kinetics, and muscle activity using the OpenSim individualized musculoskeletal model. One-way repeated measures ANOVA was used for statistical analysis. The results showed that when the heel was raised, the participant’s ankle dorsiflexion angle significantly decreased, and the percentage of ankle work was increased (p < 0.05). In addition, there was a significant increase in activation of the vastus lateralis, biceps femoris, and gastrocnemius muscles and a decrease in muscle activation of the anterior tibialis muscle (p < 0.05). An increase in knee moments and work done and a reduction in hip work were observed in male subjects (p < 0.05). In conclusion, heel raises affect lower extremity kinematics and kinetics during the barbell squat and alter the distribution of muscle activation and biomechanical loading of the joints in the lower extremity of participants to some extent, and there were gender differences in the results.

Current Consensus for Rehabilitation Protocols of the Surgically Repaired Acute Mid-Substance Achilles Rupture: A Systematic Review and Recommendations From the "GAIT" Study Group

Surgical repair of acute mid-substance Achilles tendon ruptures is performed in active patients, but the postoperative rehabilitation program is often based on the experience of the surgeon or therapist, rather than on evidence-based protocols. The aim of the study is to establish an evidence-based protocol for rehabilitation. This study is a consensus statement. The "GAIT" study group (German, American, and Italian Tendon), an informal collection of 4 experienced foot and ankle surgeons, met to address the question of what items they felt were important relative to rehabilitate a surgically repaired Achilles tendon acute rupture. Thirty-three statements were formulated. A value of 100% agreement by all the members was set to produce a proposed consensus statement. A value of 80% consensus was set to produce "strong recommendation." A systematic review of the literature was also performed. The GAIT group reach 100% agreement on the average postoperative non-weightbearing for 2.3 weeks, the foot in plantarflexion for the first 4 weeks, avoiding ROM exercises beyond neutral, and both stretching and eccentric exercise, not started before 12 weeks. Concentric bilateral heel raises should be performed after 6 weeks, and the average return to initiate sports, was 24.4 weeks. The use of a 1/8^th-1/4^th inch heel cushions in daily shoes after 8 weeks, the use of an antigravity treadmill for rehabilitation, and the return to sports based on heel raise repetitions is strongly recommended. Given lack of established verified protocols, the recommendations by our experienced panel should be considered. These proposed consensus statements could be used as a basis for larger controlled trials, and develop best practices.

Self-reported foot strike patterns and sonographic evidence of Achilles tendinopathy in asymptomatic marathon runners

It is unknown whether ultrasound findings and symptoms of Achilles tendinopathy in runners correlate with foot strike patterns. We aimed to examine the relationships among Achilles tendon ultrasound findings in runners with or without Achilles tendinopathy, their foot strike patterns, and their training regimens. We recruited marathon runners 18 years of age or older with no history of Achilles tendon pain or surgery participating in the 2018 DONNA Marathon. Participants completed surveys and underwent Achilles tendon sonographic evaluations and were categorized by foot strike patterns. Seventy-nine runners were included; 22 (28%) with forefoot, 30 (38%) midfoot, and 27 (34%) hindfoot strike patterns. Foot strike pattern was not associated with tendon hyperaemia (P = 1.00) or hypoechogenicity (P = .97), and there was no association of cross-sectional area of the Achilles tendon with peak weekly distance while training. Sonographic characteristics of Achilles tendinopathy did not correlate with foot strike patterns or training regimens. Although not statistically significant, it is worth noting that cross-sectional area was 1 mm² larger per every 1 kg/m² increase in body mass index.

Achilles tendon resting angle is able to detect deficits after an Achilles tendon rupture, but it is not a surrogate for direct measurements of tendon elongation, function or symptoms

PURPOSE

The aim of this study was to investigate how the Achilles tendon resting angle (ATRA), an indirect measurement of tendon elongation, correlates with ultrasonography (US) measurements of the Achilles tendon length 6 and 12 months after an acute ATR and relates to other clinical outcome measurements such as heel-rise height, jumping ability and patient-reported outcome measurements (PROMs).

METHODS

Patients were included following acute Achilles tendon rupture (ATR). Achilles tendon length, ATRA, heel-rise height (HRH), drop countermovement jump (Drop CMJ) and PROMs (Achilles tendon total rupture score (ATRS) and physical activity scale (PAS)) were evaluated 6 and 12 months after injury. Achilles tendon length was evaluated using US, while the ATRA was measured with a goniometer.

RESULTS

Sixty patients (13 women, 47 men), mean (SD) age 43 (9) years, with an acute ATR undergoing either surgical (35%) or non-surgical (65%) treatment were evaluated. A negative correlation (r = - 0.356, p = 0.010) between relative ATRA and tendon elongation was seen at 12 months after ATR. There were also significant positive correlations at 6 and 12 months between relative ATRA and HRH (r = 0.330, p = 0.011 and r = 0.379, p = 0.004). There were no correlations between ATRA and ATRS or ATRA and Drop CMJ, at either 6 or 12 months after the injury.

CONCLUSION

In combination with other clinical evaluations such as HRH and US, ATRA could be a clinical tool for indirect measurements of tendon elongation. However, ATRA cannot be recommended as a direct surrogate for US for determining Achilles tendon length.

LEVEL OF EVIDENCE

III.

Ground Reaction Forces during Vertical Hops Are Correlated with the Number of Supervised Physiotherapy Visits after Achilles Tendon Surgery

The objective of this study was to assess the effectiveness of, and the correlation between, an average of 42 supervised physiotherapy (SVPh) visits for the vertical ground reaction forces component (vGRF) using ankle hops during two- and one-legged vertical hops (TLH and OLH, respectively), six months after the surgical suturing of the Achilles tendon using the open method (SSATOM) via Keesler’s technique. Hypothesis: Six months of supervised physiotherapy with a higher number of visits (SPHNVs) was positively correlated with higher vGRF values during TLH and OLH. Group I comprised male patients (n = 23) after SSATOM (SVPh x = 42 visits), and Group II comprised males (n = 23) without Achilles tendon injuries. In the study groups, vGRF was measured during TLH and OLH in the landing phase using two force plates. The vGRF was normalized to the body mass. The limb symmetry index (LSI) of vGRF values was calculated. The ranges of motion of the foot and circumferences of the ankle joint and shin were measured. Then, 10 m unassisted walking, the Thompson test, and pain were assessed. A parametric test for dependent and independent samples, ANOVA and Tukey’s test for between-group comparisons, and linear Pearson’s correlation coefficient calculations were performed. Group I revealed significantly lower vGRF values during TLH and OLH for the operated limb and LSI values compared with the right and left legs in Group II (p ≤ 0.001). A larger number of visits correlates with higher vGRF values for the operated limb during TLH (r = 0.503; p = 0.014) and OLH (r = 0.505; p = 0.014). An average of 42 SVPh visits in 6 months was insufficient to obtain similar values of relative vGRF and their LSI during TLH and OLH, but the hypothesis was confirmed that SPHNVs correlate with higher relative vGRF values during TLH and OLH in the landing phase.

Functional Ankle Range of Motion but Not Peak Achilles Tendon Force Diminished With Heel-Rise and Jumping Tasks After Achilles Tendon Repair

BACKGROUND

Deficits in sporting performance after Achilles tendon repair may be due to changes in musculotendinous unit structure, including tendon elongation and muscle fascicle shortening.

PURPOSE/HYPOTHESIS

The purpose was to discern whether Achilles tendon rupture reduces triceps surae muscle force generation, alters functional ankle range of motion, or both during sports-related tasks. We hypothesized that individuals who have undergone Achilles tendon repair lack the functional ankle range of motion needed to complete sports-related tasks.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The study included individuals 1 to 3 years after treatment of Achilles tendon rupture with open repair. Participants (n = 11) completed a heel-rise task and 3 jumping tasks. Lower extremity biomechanics were analyzed using motion capture. Between-limb differences were tested using paired t test.

RESULTS

Pelvic vertical displacement was reduced during the heel-rise (mean difference, -12.8%; P = .026) but not during the jumping task (P > .1). In the concentric phase of all tasks, peak ankle plantarflexion angle (range of mean difference, -19.2% to -48.8%; P < .05) and total plantar flexor work (defined as the area under the plantar flexor torque - ankle angle curve) (range of mean difference, -9.5% to -25.7%; P < .05) were lower on the repaired side relative to the uninjured side. No significant differences were seen in peak Achilles tendon load or impulse with any of the tasks. There were no differences in plantar flexor work or Achilles tendon load parameters during eccentric phases.

CONCLUSION

Impaired task performance or increased demands on proximal joints were observed on the repaired side in tasks isolating ankle function. Tasks that did not isolate ankle function appeared to be well recovered, although functional ankle range of motion was reduced with rupture. Reduced plantar flexor muscle-tendon unit work supports previous reports that an elongated tendon and shorter muscle fascicles caused by Achilles tendon rupture constrain functional capacity. Achilles tendon peak load and impulse were not decreased, suggesting that reduced and shifted functional ankle range of motion (favoring dorsiflexion) underlies performance deficits.

CLINICAL RELEVANCE

These findings point to the need to reduce tendon elongation and restore muscle length of the triceps surae after Achilles tendon rupture in order to address musculature that is short but not necessarily weak for improved performance with sports-related activities.

Neuromechanical activation of triceps surae muscle remains altered at 3.5 years following open surgical repair of acute Achilles tendon rupture

PURPOSE

To assess whether the neuromuscular activation pattern following Achilles tendon rupture and repair may contributes to the observable functional deficits in this severe and increasingly frequent injury.

METHODS

In this study, the neuromuscular activation using surface EMG of n = 52 patients was assessed during a battery of functional performance tasks to assess potential alterations of muscular activation and recruitment. We analyzed the injured leg vs. the contralateral healthy leg at a mean of 3.5 years following open surgical repair. The testing battery included isokinetic strength testing, bipedal and single-legged heel-rise testing as well as gait analysis.

RESULTS

During isokinetic testing, we observed a higher activation integral for all triceps surae muscles of the injured side during active dorsiflexion, e.g., eccentric loading on the injured leg, while concentric plantarflexion showed no significant difference. Dynamic heel-rise testing showed a higher activation in concentric and eccentric loading for all posterior muscles on the injured side (not significant); while static heel-rise for 10 sec. revealed a significantly higher activation. Further analysis of frequency of fast Fourier-transformed EMG revealed a significantly higher median frequency in the injured leg. Gait analysis revealed a higher pre-activation of the tibialis anterior before ground contact, while medial and lateral gastrocnemius muscles of the injured leg showed a significantly higher activation during push-off phase.

CONCLUSIONS

The results of this study provide evidence on the neuromuscular changes 3.5 years following open surgical Achilles tendon repair. These complex neuromuscular changes are manifested to produce the maximum force output whilst protecting the previously injured tendon. The observed alterations may be related to an increased recruitment of type II muscle fibers which could make the muscles prone to fatigue.

LEVEL OF EVIDENCE

III.

Bipedal hopping as a new measure to detect subtle sensorimotor impairment in people with multiple sclerosis

BACKGROUND

Bipedal hopping has the potential to detect subtle multiple sclerosis (MS)-related impairments, especially among patients who "pass" typical movement tests. In this narrative review, we outline the biomechanics of bipedal hopping and propose its usefulness as a novel outcome measure for people with MS having mild disability.

METHODS

We summarize articles that (1) examined the biomechanics of jumping or hopping and (2) tested the validity and/or reliability of hopping tests. We consolidated consistencies and gaps in research and opportunities for future development of the bipedal hop test.

RESULTS

Bipedal hopping requires immense power, coordination, balance, and ability to reduce co-contraction; movement components typically affected by MS. These impairments can be measured and differentiated by examining specific variables, such as hop length (power), symmetry (coordination), center of pressure (balance), and coefficient of variability (co-contraction/spasticity). Bipedal hopping challenges these aspects of movement and exposes sensorimotor impairments that may not have been apparent during walking.

CONCLUSIONS

Testing of bipedal hopping on an instrumented walkway may detect and monitor sensorimotor control in people with MS who do not currently present with clinical deficits. Early measurement is imperative for precise rehabilitation prescription to slow disability progression prior to onset of measurable gait impairment.Implications for rehabilitationJumping and hopping tests detect lower limb and balance impairments in children, athletes, and older adults.Bipedal hop test measures multiple domains: power, coordination, balance, and muscle timing.Bipedal hop test may expose subtle sensorimotor impairments in people with multiple sclerosis.Multiple variables measured can discern type of sensorimotor impairment to direct personalized rehabilitation programs.

Impact of seated and standing positions on triceps surae muscle activation in unilateral Achilles tendon rupture

Heel-rises are commonly used in the rehabilitation of individuals following Achilles tendon rupture, however, the impact of tendon elongation on triceps surae activation in seated versus standing positions has not been investigated. The purpose of this study was to investigate changes in triceps surae activation during seated compared to standing heel-rises in individuals with Achilles tendon rupture and its relationship to tendon elongation. Ten individuals with a history of Achilles tendon rupture were included in this study. Muscle activity using electromyography was examined during a heel-rise task in seated (unilateral) and standing (bilateral) positions. Soleus activity was not significantly different between sitting and standing on both the ruptured and uninjured side. On the ruptured, side there were no differences in medial or lateral gastrocnemius activity between sitting and standing; however, on the uninjured side medial and lateral gastrocnemius activity was lower in sitting compared to standing. The results of this study suggest that neuromuscular changes in triceps surae activation occur following Achilles tendon rupture. The seated heel-rise position can be used to strengthen all muscles of the triceps surae and is useful when the patient is unable to perform a standing heel-rise.

Medial gastrocnemius muscle remodeling correlates with reduced plantarflexor kinetics 14 weeks following Achilles tendon rupture

Deficits in plantarflexor kinetics are associated with poor outcomes in patients following Achilles tendon rupture. In this longitudinal study, we analyzed the fascicle length and pennation angle of the medial gastrocnemius muscle and the length of the Achilles tendon using ultrasound imaging. To determine the relationship between muscle remodeling and deficits in plantarflexor kinetics measured at 14 wk after injury, we correlated the reduction in fascicle length and increase in pennation angle with peak torque measured during isometric and isokinetic plantarflexor contractions. We found that the medial gastrocnemius underwent an immediate change in structure, characterized by decreased length and increased pennation of the muscle fascicles. This decrease in fascicle length was coupled with an increase in tendon length. These changes in muscle-tendon structure persisted throughout the first 14 wk following rupture. Deficits in peak plantarflexor torque were moderately correlated with decreased fascicle length at 120 degrees per second (R² = 0.424, P = 0.057) and strongly correlated with decreased fascicle length at 210 degrees per second (R² = 0.737, P = 0.003). However, increases in pennation angle did not explain functional deficits. These findings suggest that muscle-tendon structure is detrimentally affected following Achilles tendon rupture. Plantarflexor power deficits are positively correlated with the magnitude of reductions in fascicle length. Preserving muscle structure following Achilles tendon rupture should be a clinical priority to maintain plantarflexor kinetics.NEW & NOTEWORTHY In our study, we found that when the Achilles tendon ruptures due to excessive biomechanical loading, the neighboring skeletal muscle undergoes rapid changes in its configuration. The magnitude of this muscle remodeling explains the amount of ankle power loss demonstrated by these patients once their Achilles tendons are fully healed. These findings highlight the interconnected relationship between muscle and tendon. Isolated injuries to the tendon stimulate detrimental changes to the muscle, thereby limiting joint-level function.