Epidemiology of quadriceps muscle strain injuries in elite male Australian football players.

OBJECTIVE: To describe the epidemiology of quadriceps muscle strain injury (QMSI) in elite Australian Football League (AFL) players, explore recovery milestones and determine whether recovery is impacted by factors such as injury type (index vs. re-injury), the primary muscle injured and the mechanism of injury. MEASURES: All QMSI data reported to the Soft Tissue Injury Registry of the AFL from the 2014 to 2020 seasons were evaluated. Player demographic data, circumstances of injury, MRI reports and recovery outcomes following injury were extracted. Descriptive statistics and frequency distributions are presented. Recovery outcomes for injury type, primary muscle injured and the mechanism of injury were compared using univariate analyses. RESULTS: There were 164 QMSIs from 122 players reported (134 index; 30 re-injuries). Almost all (91.3%) QMSIs involved the rectus femoris. Half (48.4%) of the QMSIs occurred during kicking and most commonly affected the dominant kicking leg (72%). The majority occurred at training (64.6%). All re-injuries involved the rectus femoris, most occurred from kicking (63.0%) and within 6 months of the preceding injury (70%). The mean return to play (RTP) time was 25.4 days (95%CI = 22.6-28.2) and rectus femoris injuries took around 14 days longer to RTP than vastii injuries (p = 0.001). QMSIs with a kicking mechanism took the longest to RTP of all injury mechanisms. CONCLUSION: In AFL players, QMSIs occur mostly in the dominant leg from a kicking mechanism. Rectus femoris injuries are more prevalent and result in longer RTP time frames. Re-injuries exclusively involved the rectus femoris, primarily from kicking.

How muscles maximize performance in accelerated sprinting.

We sought to provide a more comprehensive understanding of how the individual leg muscles act synergistically to generate a ground force impulse and maximize the change in forward momentum of the body during accelerated sprinting. We combined musculoskeletal modelling with gait data to simulate the majority of the acceleration phase (19 foot contacts) of a maximal sprint over ground. Individual muscle contributions to the ground force impulse were found by evaluating each muscle's contribution to the vertical and fore-aft components of the ground force (termed "supporter" and "accelerator/brake," respectively). The ankle plantarflexors played a major role in achieving maximal-effort accelerated sprinting. Soleus acted primarily as a supporter by generating a large fraction of the upward impulse at each step whereas gastrocnemius contributed appreciably to the propulsive and upward impulses and functioned as both accelerator and supporter. The primary role of the vasti was to deliver an upward impulse to the body (supporter), but these muscles also acted as a brake by retarding forward momentum. The hamstrings and gluteus medius functioned primarily as accelerators. Gluteus maximus was neither an accelerator nor supporter as it functioned mainly to decelerate the swinging leg in preparation for foot contact at the next step. Fundamental knowledge of lower-limb muscle function during maximum acceleration sprinting is of interest to coaches endeavoring to optimize sprint performance in elite athletes as well as sports medicine clinicians aiming to improve injury prevention and rehabilitation practices.

Muscle contributions to tibiofemoral shear forces and valgus and rotational joint moments during single leg drop landing.

Anterior cruciate ligament (ACL) injuries commonly occur during single-leg landing tasks and are a burdensome condition. Previous studies indicate that muscle forces play an important role in controlling ligamentous loading, yet these studies have typically used cadaveric models considering only the knee-spanning quadriceps, hamstrings, and gastrocnemius muscle groups. Any muscles (including non-knee-spanning muscles) capable of opposing the anterior shear joint reaction force and the valgus joint reaction moment are thought to have the greatest potential for protecting the ACL from injury. Thus, the purpose of this study was to investigate how lower-limb muscles modulate knee joint loading during a single-leg drop landing task. An electromyography-informed neuromusculoskeletal modeling approach was used to compute lower-limb muscle force contributions to the anterior shear joint reaction force and the valgus joint reaction moment at the knee during a single-leg drop landing task. The average shear joint reaction force ranged from 153 N of anterior shear force to 744 N of posterior shear force. The muscles that generated the greatest posterior shear force were the soleus, medial hamstrings, and biceps femoris, contributing up to 393 N, 359 N, and 162 N, respectively. The average frontal plane joint reaction moment ranged from a 19 Nm varus moment to a 6 Nm valgus moment. The valgus moment was primarily opposed by the gluteus medius, gluteus minimus, and soleus, with these muscles providing contributions of up to 38, 22, and 20 Nm toward a varus moment, respectively. The findings identify key muscles that mitigate loads on the ACL.

Calf muscle strain injuries in elite Australian Football players: A descriptive epidemiological evaluation.

BACKGROUND: Calf muscle strain injuries (CMSI) show consistent rates of prevalence and re-injury in elite Australian Football players. An epidemiological evaluation is warranted to better understand the clinical presentation and recovery of CMSI. PURPOSE: First, to describe the epidemiology of CMSI in elite Australian Football players. Second, to determine if recovery following injury is different according to: (a) injury type (index vs re-injury); (b) muscle injured (soleus vs gastrocnemius); and (c) mechanism of injury (running-related activity vs non running-related activity). STUDY DESIGN: Descriptive epidemiological. METHODS: Data retrieved from the Soft Tissue injury Registry of the Australian Football League were analyzed. Sixteen clubs submitted data on CMSI from 2014 to 2017. Data included: player characteristics, training and match history at the time of injury, MRI, and the time to reach recovery milestones. RESULTS: One hundred and eighty-four CMSI were included (149 index injuries; 35 re-injuries). Soleus injuries were most prevalent (84.6%). Soleus injuries took 25.4 ± 16.2 days to return to play, whereas gastrocnemius injuries took 19.1 ± 14.1 days (P = .097). CMSI sustained during running-related activities took approximately 12 days longer to recover than injuries sustained during non running-related activities (P = .001). Compared to index injuries, re-injuries involved older players (P = .03) and significantly more time was taken to run at >90% of maximum speed, return to full training, and return to play (P ≤ .001). Almost all of the observed re-injuries involved soleus (91.4%). CONCLUSION: Soleus injuries are more prevalent than gastrocnemius injuries in elite Australian Football players. Prognosis appears to be influenced by clinical factors, with CMSI sustained during running-related activities and re-injuries needing more time to recover.

Lower-limb joint mechanics during maximum acceleration sprinting.

We explored how humans adjust the stance phase mechanical function of their major lower-limb joints (hip, knee, ankle) during maximum acceleration sprinting. Experimental data [motion capture and ground reaction force (GRF)] were recorded from eight participants as they performed overground sprinting trials. Six alternative starting locations were used to obtain a dataset that incorporated the majority of the acceleration phase. Experimental data were combined with an inverse-dynamics-based analysis to calculate lower-limb joint mechanical variables. As forward acceleration magnitude decreased, the vertical GRF impulse remained nearly unchanged whereas the net horizontal GRF impulse became smaller as a result of less propulsion and more braking. Mechanical function was adjusted at all three joints, although more dramatic changes were observed at the hip and ankle. The impulse from the ankle plantar-flexor moment was almost always larger than those from the hip and knee extensor moments. Forward acceleration magnitude was linearly related to the impulses from the hip extensor moment (R2=0.45) and the ankle plantar-flexor moment (R2=0.47). Forward acceleration magnitude was also linearly related to the net work done at all three joints, with the ankle displaying the strongest relationship (R2=0.64). The ankle produced the largest amount of positive work (1.55±0.17 J kg-1) of all the joints, and provided a significantly greater proportion of the summed amount of lower-limb positive work as running speed increased and forward acceleration magnitude decreased. We conclude that the hip and especially the ankle represent key sources of positive work during the stance phase of maximum acceleration sprinting.

Impaired ankle joint mechanics during running can be resolved in people with traumatic brain injury.

OBJECTIVES: 1) To compare lower-limb joint mechanics during running for people with traumatic brain injury (TBI) to equivalent data obtained from a group of healthy controls (HCs); and 2) To determine if deficits identified in biomechanical variables during running for people with TBI responded to a six-month period of rehabilitation. METHODS: Running biomechanics data were recorded from 12 people with TBI who were attending a large metropolitan rehabilitation hospital for mobility limitations, and a comparative sample of 10 HCs at baseline and six-month follow-up. MAIN MEASURES: Average power absorbed and generated at the hip, knee and ankle joints during stance. RESULTS: Compared to HCs, participants with TBI at baseline ran with greater average power absorption at the hip (-0.27 W/kg vs -0.61 W/kg; p< 0.05), reduced average power absorption at the knee (-2.03 W/kg vs -1.02 W/kg; p< 0.05) and reduced average power generation at the ankle (2.86 W/kg vs 2.06 W/kg; p< 0.05). Only average power generation at the ankle improved following six-months of rehabilitation for the participants with TBI (2.06 W/kg vs 2.79 W/kg; p< 0.05). CONCLUSION: For the participants with TBI in the present study, recovery of high-level mobility following rehabilitation occurred alongside an improvement in ankle joint mechanics during running.

Athletes Rated as Poor Single-Leg Squat Performers Display Measurable Differences in Single-Leg Squat Biomechanics Compared With Good Performers.

CONTEXT: It is important to validate single-leg squat visual rating criteria used in clinical practice and research. Foot orthoses may improve single-leg squat performance in those who demonstrate biomechanics associated with increased risk of lower limb injury. OBJECTIVE: Validate visual rating criteria proposed by Crossley et al, by determining whether athletes rated as poor single-leg squat performers display different single-leg squat biomechanics than good performers; and evaluate immediate effects of foot orthoses on single-leg squat biomechanics in poor performers. DESIGN: Comparative cross-sectional study. SETTING: University laboratory. PARTICIPANTS: 79 asymptomatic athletes underwent video classification of single-leg squat performance based on established visual rating criteria (overall impression, trunk posture, pelvis "in space," hip movement, and knee movement), and were rated as good (n = 23), fair (n = 41), or poor (n = 15) performers. INTERVENTION: A subset of good (n = 16) and poor (n = 12) performers underwent biomechanical assessment, completing 5 continuous single-leg squats on their dominant limb while 3-dimensional motion analysis and ground reaction force data were recorded. Poor performers repeated the task standing on prefabricated foot orthoses. MAIN OUTCOME MEASURES: Peak external knee adduction moment (KAM) and peak angles for the trunk, hip, knee, and ankle. RESULTS: Compared with good performers, poor performers had a significantly lower peak KAM (mean difference = 0.11 Nm/kg, 95% confidence interval = 0.02 to 0.2 Nm/kg), higher peak hip adduction angle (-4.3°, -7.6° to -0.9°), and higher peak trunk axial rotation toward their stance limb (3.8°, 0.4° to 7.2°). Foot orthoses significantly increased the peak KAM in poor performers (-0.06 Nm/kg, -0.1 to -0.01 Nm/kg), with values approximating those observed in good performers. CONCLUSIONS: Findings validate Crossley et al's visual rating criteria for single-leg squat performance in asymptomatic athletes, and suggest that "off-the-shelf" foot orthoses may be a simple intervention for poor performers to normalize the magnitude of the external KAM during single-leg squat.

Is quality of life following hip arthroscopy in patients with chondrolabral pathology associated with impairments in hip strength or range of motion?

INTRODUCTION: If physical impairments that are associated with poorer outcomes can be identified in people with chondrolabral hip pathology, then rehabilitation programmes that target such modifiable impairments could potentially be established to improve quality of life. The aim of this study was to examine the relationship between quality-of-life PROs and physical impairment measurements in people with chondrolabral pathology post-hip arthroscopic surgery. METHODS: This was a cross-sectional study where multiple stepwise linear regression analyses were conducted to determine which physical impairment measurements were most associated with poorer quality-of-life patient-reported outcomes (PROs). Eighty-four patients (42 women; all aged 36 ± 10 years) with hip chondrolabral pathology 12- to 24-month post-hip arthroscopy were included. The Hip disability and Osteoarthritis Outcome Score Quality-of-life (HOOS-Q) subscale and International Hip Outcome Tool (IHOT-33) PROs were collected. Measurements of active hip ROM and strength were assessed. RESULTS: Modifiable post-surgical physical impairments were associated with PRO in patients with chondrolabral pathology. Greater hip flexion ROM was independently associated with better scores in both HOOS-Q and IHOT-33 (adjusted r 2 values ranged from 0.249 to 0.341). Greater hip adduction strength was independently associated with better HOOS-Q and IHOT-33 (adjusted r 2 0.227-0.317). Receiver Operator Curve analyses determined that the limit value for hip flexion ROM was 100° (sensitivity 92 %, specificity 75 %), and hip adduction strength was 0.86 Nm/kg (sensitivity 96 %, specificity 70 %). CONCLUSIONS: Hip flexion ROM and adduction strength were associated with better quality-of-life PRO scores in patients with chondrolabral pathology 12- to 24-month post-hip arthroscopy. These impairments could be targeted by clinicians designing rehabilitation programmes to this patient group. LEVEL OF EVIDENCE: Cross-sectional study, Level IV.

Modulation of work and power by the human lower-limb joints with increasing steady-state locomotion speed.

We investigated how the human lower-limb joints modulate work and power during walking and running on level ground. Experimental data were recorded from seven participants for a broad range of steady-state locomotion speeds (walking at 1.59±0.09 m s(-1) to sprinting at 8.95±0.70 m s(-1)). We calculated hip, knee and ankle work and average power (i.e. over time), along with the relative contribution from each joint towards the total (sum of hip, knee and ankle) amount of work and average power produced by the lower limb. Irrespective of locomotion speed, ankle positive work was greatest during stance, whereas hip positive work was greatest during swing. Ankle positive work increased with faster locomotion until a running speed of 5.01±0.11 m s(-1), where it plateaued at ∼1.3 J kg(-1). In contrast, hip positive work during stance and swing, as well as knee negative work during swing, all increased when running speed progressed beyond 5.01±0.11 m s(-1). When switching from walking to running at the same speed (∼2.0 m s(-1)), the ankle's contribution to the average power generated (and positive work done) by the lower limb during stance significantly increased from 52.7±10.4% to 65.3±7.5% (P=0.001), whereas the hip's contribution significantly decreased from 23.0±9.7% to 5.5±4.6% (P=0.004). With faster running, the hip's contribution to the average power generated (and positive work done) by the lower limb significantly increased during stance (P<0.001) and swing (P=0.003). Our results suggest that changing locomotion mode and faster steady-state running speeds are not simply achieved via proportional increases in work and average power at the lower-limb joints.

Terminology and definitions on groin pain in athletes: building agreement using a short Delphi method.

BACKGROUND: Groin pain in athletes occurs frequently and can be difficult to treat, which may partly be due to the lack of agreement on diagnostic terminology. OBJECTIVE: To perform a short Delphi survey on terminology agreement for groin pain in athletes by a group of experts. METHODS: A selected number of experts were invited to participate in a Delphi questionnaire. The study coordinator sent a questionnaire, which consisted of demographic questions and two 'real-life' case reports of athletes with groin pain. The experts were asked to complete the questionnaire and to provide the most likely diagnosis for each case. Questionnaire responses were analysed by an independent researcher. The Cohen's κ statistic was used to evaluate the level of agreement between the diagnostic terms provided by the experts. RESULTS: Twenty-three experts participated (96% of those invited). For case 1, experts provided 9 different terms to describe the most likely diagnosis; for case 2, 11 different terms were provided to describe the most likely diagnosis. With respect to the terms provided for the most likely diagnosis, the Cohen's κ was 0.06 and 0.002 for case 1 and 2, respectively. This heterogeneous taxonomy reflects only a slight agreement between the various diagnostic terms provided by the selected experts. CONCLUSIONS: This short Delphi survey of two 'typical, straightforward' cases demonstrated major inconsistencies in the diagnostic terminology used by experts for groin pain in athletes. These results underscore the need for consensus on definitions and terminology on groin pain in athletes.

Doha agreement meeting on terminology and definitions in groin pain in athletes.

BACKGROUND: Heterogeneous taxonomy of groin injuries in athletes adds confusion to this complicated area. AIM: The 'Doha agreement meeting on terminology and definitions in groin pain in athletes' was convened to attempt to resolve this problem. Our aim was to agree on a standard terminology, along with accompanying definitions. METHODS: A one-day agreement meeting was held on 4 November 2014. Twenty-four international experts from 14 different countries participated. Systematic reviews were performed to give an up-to-date synthesis of the current evidence on major topics concerning groin pain in athletes. All members participated in a Delphi questionnaire prior to the meeting. RESULTS: Unanimous agreement was reached on the following terminology. The classification system has three major subheadings of groin pain in athletes: 1. Defined clinical entities for groin pain: Adductor-related, iliopsoas-related, inguinal-related and pubic-related groin pain. 2. Hip-related groin pain. 3. Other causes of groin pain in athletes. The definitions are included in this paper. CONCLUSIONS: The Doha agreement meeting on terminology and definitions in groin pain in athletes reached a consensus on a clinically based taxonomy using three major categories. These definitions and terminology are based on history and physical examination to categorise athletes, making it simple and suitable for both clinical practice and research.

Tendon elastic strain energy in the human ankle plantar-flexors and its role with increased running speed.

The human ankle plantar-flexors, the soleus and gastrocnemius, utilize tendon elastic strain energy to reduce muscle fiber work and optimize contractile conditions during running. However, studies to date have considered only slow to moderate running speeds up to 5 m s(-1). Little is known about how the human ankle plantar-flexors utilize tendon elastic strain energy as running speed is advanced towards maximum sprinting. We used data obtained from gait experiments in conjunction with musculoskeletal modeling and optimization techniques to calculate muscle-tendon unit (MTU) work, tendon elastic strain energy and muscle fiber work for the ankle plantar-flexors as participants ran at five discrete steady-state speeds ranging from jogging (~2 m s(-1)) to sprinting (≥8 m s(-1)). As running speed progressed from jogging to sprinting, the contribution of tendon elastic strain energy to the positive work generated by the MTU increased from 53% to 74% for the soleus and from 62% to 75% for the gastrocnemius. This increase was facilitated by greater muscle activation and the relatively isometric behavior of the soleus and gastrocnemius muscle fibers. Both of these characteristics enhanced tendon stretch and recoil, which contributed to the bulk of the change in MTU length. Our results suggest that as steady-state running speed is advanced towards maximum sprinting, the human ankle plantar-flexors continue to prioritize the storage and recovery of tendon elastic strain energy over muscle fiber work.

Patellofemoral joint loading during stair ambulation in people with patellofemoral osteoarthritis.

OBJECTIVE: To determine whether people with patellofemoral (PF) joint osteoarthritis (OA) ascend and descend stairs with different PF joint loading, knee joint moments, lower limb kinematics, and muscle forces compared to healthy people. METHODS: We recruited 17 participants with isolated PF joint OA, 13 participants with concurrent PF joint OA and tibiofemoral (TF) joint OA, and 21 age-matched controls. Joint kinematics and ground reaction forces were measured while participants ascended and descended stairs at a self-selected speed. Musculoskeletal computer modeling was used to determine lower limb muscle forces and the PF joint reaction force, and these parameters were compared between groups by analysis of variance. RESULTS: Compared to their healthy counterparts, participants with isolated PF joint OA and participants with concurrent PF and TF joint OA ascended and descended stairs with lower knee extension moments, lower quadriceps muscle forces, lower PF joint reaction forces, and increased anterior pelvic tilt. Participants with OA also ascended stairs with increased hip flexion angles and descended stairs with smaller knee flexion angles and smaller hip abductor muscle forces. No differences were evident between the two groups with OA. CONCLUSION: Compared to their healthy counterparts, people with PF joint OA (with or without concurrent TF joint OA) exhibit lower PF joint reaction forces during stair ascent and descent, in conjunction with lower knee extension moments and lower quadriceps muscle forces.

Hip chondropathy at arthroscopy: prevalence and relationship to labral pathology, femoroacetabular impingement and patient-reported outcomes.

BACKGROUND: This study aimed to describe chondropathy prevalence in adults who had undergone hip arthroscopy for hip pain. The relationships between chondropathy severity and (1) participant characteristics; and (2) patient-reported outcomes (PROs) at initial assessment (∼18 months postsurgery) and over a further 12 months (∼30 months postsurgery) were evaluated. Finally, the relationships between chondropathy and coexisting femoroacetabular impingement (FAI) and labral pathology at the time of surgery were evaluated. METHODS: 100 consecutive patients (36±12 years) who underwent hip arthroscopy 18 months previously participated. Hip Osteoarthritis and Disability Outcome Score (HOOS) and International Hip Outcome Tool (iHOT-33) data were collected prospectively at 18 months postsurgery and at 30 months postsurgery. Surgical data were collected retrospectively. Participants were grouped: Outerbridge grade 0, no chondropathy; Outerbridge grade I-II, mild chondropathy; Outerbridge III-IV, severe chondropathy. The presence of FAI or labral pathology was noted. RESULTS: The prevalence of chondropathy (≥grade I) at hip arthroscopy was 72%. Participants with severe chondropathy were significantly worse for all HOOS subscales and the iHOT-33 at 18 months postsurgery (HOOS-symptoms (p=0.017); HOOS-pain (p=0.024); HOOS-activity (p=0.009); HOOS-sport (p=0.004); HOOS-quality-of-life (p=0.006); iHOT-33 (p=0.013)) than those with no chondropathy. At 12-month follow-up, HOOS-quality-of-life in those without chondropathy was the only PRO that improved. Relative risk of coexisting chondropathy with labral pathology or FAI was 40%. CONCLUSIONS: Chondropathy was prevalent, and associated with increasing age, coexisting labral pathology or FAI. Severe chondropathy was associated with worse pain and function at 18 months postsurgery. Little improvements were observed in participants over a further 12 months, regardless of chondropathy status.

Lower Limb Joint Mechanics during Maximal Accelerative and Decelerative Running.

INTRODUCTION: Maximal acceleration and deceleration tasks are frequently required in team sports, often occurring rapidly in response to external stimuli. Accelerating and decelerating can be associated with lower limb injuries; thus, knowledge of joint mechanics during these tasks can improve the understanding of both human high performance and injury mechanisms. The current study investigated the fundamental differences in lower limb joint mechanics when accelerating and decelerating by directly comparing the hip, knee, and ankle joint moments and work done between the two tasks. METHODS: Twenty participants performed maximal effort acceleration and deceleration trials, with three-dimensional marker trajectories and ground reaction forces collected simultaneously. Experimental data were combined with inverse dynamics analysis to compute joint moments and work. RESULTS: Net joint work for all lower limb joints was positive during acceleration and negative during deceleration. This occurred because of significantly greater positive work production from the ankle and hip during acceleration and significantly greater negative work production from all joints during deceleration. The largest contributions to positive work during acceleration came from the ankle, followed by the hip and knee joints, whereas the largest contributions to negative work during deceleration came from the knee and hip joints, followed by the ankle. Peak joint moments were significantly greater when decelerating compared with accelerating, except for the peak ankle plantarflexion and hip flexion moments, which were significantly greater when accelerating. CONCLUSIONS: Our findings may help to guide training interventions, which aim to enhance the performance of acceleration and deceleration tasks, while also mitigating the associated injury risk.

Walking biomechanics in women with patellofemoral osteoarthritis differ compared to men with and women without patellofemoral osteoarthritis.

BACKGROUND: Differences in walking biomechanics between women and men with patellofemoral joint (PF) osteoarthritis (OA) may contribute to the development or progression of persistent symptoms in people with PFJ OA. OBJECTIVE: Evaluate how walking biomechanics of women with PF OA differ from: (i) men with PFJ OA; and (ii) women without PF OA. Second, explore the relationship between knee-related symptoms/function and walking biomechanics in individuals with PF OA, and whether these are modified by sex. METHODS: Sixty-seven individuals with PF OA (43 women) and 14 women without PF OA were included. Biomechanics data were recorded during walking. Patient-reported symptoms and function were obtained using the Knee injury and Osteoarthritis Outcome Score. Differences in continuous biomechanical data were assessed using statistical parametric mapping, with discrete data and relationships evaluated using linear models. RESULTS: Women with PF OA walked with a greater hip adduction angle throughout stance (t > 2.757) and lower impulses for the hip flexion, knee flexion, and ankle dorsiflexion moments (adjusted mean differences [95 % CI]:3.3 × 10-2 [-4.9 × 10-2, -1.6 × 10-2], -2.9 × 10-2 [-5.3 × 10-2, -0.4 × 10-2], -5.1 × 10-2 [-8.2 × 10-2, -2.0 × 10-2] Nms/kg, respectively) compared to men with PF OA. Compared to their asymptomatic peers, women with PF OA displayed a 5° offset towards greater hip flexion. Higher knee adduction moment impulse correlated with worse KOOS-ADL scores in men, not women. CONCLUSION: Observed biomechanical differences were small in nature with moderate to weak relationship observed with the KOOS. Findings were not limited to the knee, indicating that women with PF OA display unique biomechanical features across the kinetic-chain.

Mobility after traumatic brain injury: relationships with ankle joint power generation and motor skill level.

BACKGROUND: Reduced balance, spasticity, contractures, muscle weakness, and motor skill levels may all contribute to mobility limitations after traumatic brain injury (TBI), yet the key physical impairments that contribute to mobility limitations remain unclear. OBJECTIVE: The aim of this study was to determine which physical impairments best predict mobility performance after a period of 6 months of rehabilitation. PARTICIPANTS: Participants with TBI were selected if they were receiving therapy for mobility limitations but were able to walk without physical assistance. OUTCOME MEASURES: The clinical assessment included measures of balance, spasticity, and contracture, and 3-dimensional quantitative gait analysis was used to quantify joint power generation and motor skill level on 31 adults with severe TBI. Mobility outcome was quantified with the high-level mobility assessment tool. RESULTS: Two variables, ankle joint power generation during the push-off phase of gait and motor skill level, explained 66.5% of the variability in mobility outcome. Balance, strength, and mobility performance, all improved significantly over the 6 months of rehabilitation. Only 2 participants had contractures, which affected mobility. Balance disorders were prevalent and improved with rehabilitation, yet they contributed to only a limited extent to the level of recovery in mobility. CONCLUSION: Ankle joint power generation at push-off was the strongest predictor of mobility outcome after 6 months of rehabilitation in ambulant people with TBI.

Self-selected walking speed predicts ability to run following traumatic brain injury.

OBJECTIVE: To identify factors that predict running ability following traumatic brain injury (TBI), and to quantify performance thresholds for these predictors. DESIGN: Cross-sectional cohort study. PARTICIPANTS: One hundred fourteen people with TBI. OUTCOME MEASURES: Self-selected walking speed, the high-level mobility assessment tool, postural stability (lateral center of mass displacement), ankle power generation at push-off and quality of gait performance (Gait Profile Score). RESULTS: All predictor variables were all strongly associated with the ability to run. However, only self-selected walking speed contributed significantly to the final result. Investigation of performance thresholds for self-selected walking speed indicated that following TBI, people who walk at speeds of 1.0 m/s or higher are 16.9 times more likely of being able to run than for those who walk at speeds of less than 1.0 m/s. CONCLUSIONS: Self-selected walking speeds higher than 1.0 m/s greatly increase the likelihood of running following brain injury. The 1.0 m/s threshold, although slower than able-bodied self-selected walking speeds, may be an important indicator of the ability to run in this population.

Stretch and activation of the human biarticular hamstrings across a range of running speeds.

PURPOSE: The human biarticular hamstrings [semimembranosus (SM), semitendinosus (ST) and biceps femoris long head (BF(LH))] have an important role in running. This study determined how hamstrings neuro-mechanical behaviour changed with faster running, and whether differences existed between SM, ST and BF(LH). METHODS: Whole-body kinematics and hamstrings electromyographic (EMG) activity were measured from seven participants running at four discrete speeds (range: 3.4 ± 0.1 to 9.0 ± 0.7 m/s). Kinematic data were combined with a three-dimensional musculoskeletal model to calculate muscle-tendon unit (MTU) stretch and velocity. Activation duration and magnitude were determined from EMG data. RESULTS: With faster running, MTU stretch and velocity patterns remained similar, but maxima and minima significantly increased. The hamstrings were activated from foot-strike until terminal stance or early swing, and then again from mid-swing until foot-strike. Activation duration was similar with faster running, whereas activation magnitude significantly increased. Hamstrings activation almost always ended before minimum MTU stretch, and it always started before maximum MTU stretch. Comparing the hamstrings, maximum MTU stretch was largest for BF(LH) and smallest for ST irrespective of running speed, while the opposite was true for peak-to-peak MTU stretch. Furthermore, peak MTU shortening velocity was largest for ST and smallest for BF(LH) at all running speeds. Finally, for the two fastest running speeds, the amount of MTU stretch that occurred during terminal swing after activation had started was less for BF(LH) compared to SM and ST. CONCLUSION: Differences were evident in biarticular hamstrings neuro-mechanical behaviour during running. Such findings have implications for hamstrings function and injury.