Muscle force contributions to knee joint loading

Anterior cruciate ligament (ACL) injuries are one of the most common knee injuries suffered by athletic populations. ACL injuries are particularly burdensome due to potential surgical requirements, extensive rehabilitation time and associated financial costs for the individual and the community. Additionally, ACL injuries are associated with increased risk of early onset knee osteoarthritis. As such, ACL injury preventative and rehabilitative strategies are of paramount importance. ACL injuries typically occur during non-contact dynamic tasks, such as unanticipated sidestep cutting. At the time of injury, the knee joint experiences relatively large degrees of knee valgus and rotation (either internal or external) and high mechanical loads. These loading patterns, along with the anterior shear force, are known to increase loads on the ACL, especially in combination with each other. Muscles produce forces that can cause and oppose these knee joint loads, and therefore play a critical role in dictating the size and the nature of the loads experienced by the ACL. Prior research has investigated the role of muscle force in ACL load development, and has indicated that the hamstrings are most capable of reducing ACL loads. Subsequently, any pathology that may influence hamstring function may increase the risk of ACL injury. Some studies have shown that participants with a history of hamstring strain injury (HSI) have lower knee flexor strength and hamstring muscle activation compared to healthy legs. Consequently, a relationship between prior HSI and ACL injury could exist. However, establishing this relationship is difficult due to the relatively low incidence of ACL injury. Subsequently, prospective studies aiming to investigate this relationship would be very costly, due to the requirement of very large sample sizes and long follow-up periods. Additionally, such a relationship would depend on the functional role of the hamstring muscle group during potentially ACL-injurious manoeuvres such as sidestep cutting, which has not been fully elucidated. Furthermore, given the multi-planar demands of tasks that place the ACL at risk of injury, better understanding the contribution of the individual hamstring muscles to knee joint loading relative to the other lower-limb muscles is imperative. Musculoskeletal simulation offers the ability to analyse cause-effect relationships between muscle force development and joint loading whilst accounting for whole body kinematics. This analysis could not only reveal the true potential of the hamstring muscles in protecting the ACL, but could also elucidate the role of other muscles which have been less studied. The purpose of this doctoral thesis was to explore the relationship between muscle forces in the development of knee joint loading during potentially injurious manoeuvres, as this knowledge may be used to inform interventions that aim to reduce ACL injury risk. Given recent hypotheses suggesting a possible association between prior injury to the hamstrings and an increased risk of ACL injury and based on the current literature, which indicates that the hamstrings are one of the most important muscle groups for unloading the ACL, the focus of the first study (Chapter 4) was to determine the impact of HSI on hamstring function. Specifically, a systematic review and meta-analysis was used to compare knee flexor strength and flexibility in previously injured legs to the uninjured contralateral leg. It was found that deficits in concentric and eccentric strength (and associated hamstring to quadriceps strength ratios) were present at and after return to play. Isometric strength deficits were also present after HSI, but these recovered within 20-30 days. Hamstring flexibility deficits were also found after HSI, but these recovered within 40-50 days post injury. A secondary aim of this study was to document the totality of measures reported in the literature that have been taken in previously injured hamstrings. The review revealed that knee flexor and extensor strength were the most commonly assessed variables in participants with previously injured hamstrings and that there are few studies which examine the function of other lower-limb muscles. Furthermore, there was limited information examining multi-planar movements. The findings of the review highlighted the need to better understand how the hamstrings contribute to knee joint loading, relative to the contribution of other lower-limb muscles, to better guide future work examining the link between prior HSI and future ACL injury. The conclusions obtained from Chapter 4 informed the direction of the three subsequent chapters. The focus of the second study (Chapter 5) was to investigate the contribution of the hamstrings to ACL loading during the weight acceptance phase of an unanticipated sidestep cut relative to other lower-limb muscles. A musculoskeletal modelling approach was used to determine how different lower-limb muscles contribute to the key markers of ACL loading, namely the anteroposterior tibiofemoral shear force, and the valgus and rotation reaction moments. It was found that the hamstrings and gluteal muscles play a dominant role in protecting the ACL, by opposing the anterior shear force and valgus reaction moment, respectively. These same muscle groups were found to oppose each other in the transverse plane, thus limiting knee rotation loading. The focus of the third study (Chapter 6) was to determine the contribution of the hamstrings to the medial and lateral tibiofemoral compartment contact force during unanticipated sidestep cutting relative to other lower-limb muscles. This was because ACL injuries rarely occur in isolation, and are associated with long-term degeneration of articular knee cartilage. A custom musculoskeletal model was created with a modified knee joint mechanism, which permitted the computation of tibiofemoral compartment contact forces via a dynamic equilibrium approach. It was found that medial tibiofemoral contact loading was primarily produced by the vasti, gluteus medius and gluteus maximus and the medial gastrocnemius, whilst lateral tibiofemoral loading was produced primarily by the vasti, soleus, and the medial and lateral gastrocnemius. The medial hamstrings tended to load both compartments, whilst the biceps femoris long head loaded the lateral compartment and induced a relatively small decompression impulse in the medial compartment. Additionally, it was found that most muscles tended to compress both compartments, whilst other muscles had the ability to compress one compartment and decompress the other. The focus of the fourth study (Chapter 7) was to determine how the hamstrings contribute to coordinating the stance phase of an unanticipated sidestep cut. A musculoskeletal modelling approach was used to estimate lower-limb muscle forces, and a ground reaction force (GRF) decomposition method was used to determine how muscles contributed to the GRFs. It was found that bodyweight support is primarily modulated by the vasti, gluteus maximus, soleus, and gastrocnemius. These same muscles, along with the hamstrings, were also the primary modulators of anteroposterior progression. By contributing to the medial GRF, the vasti, gluteus maximus and gluteus medius were primarily responsible for redirecting the centre-of-mass toward the cutting direction. This program of research has identified the contribution of the hamstrings, as well as other lower-limb muscles, to knee joint loading and performance during a change-of-direction task. The first study synthesised the retrospective evidence base investigating hamstring strength and flexibility in participants with a history of HSI. This study also identified that assessments of function post HSI tend to focus mostly on the hamstrings during isolated strength assessments, neglecting other lower-limbs muscles. This highlighted the need to better understand the hamstrings role in potentially ACL injurious tasks, relative to other lower-limb muscles. In these investigations the hamstrings were found to be an important muscle group to oppose anterior shear forces during unanticipated sidestep cutting, whilst other non-knee-spanning muscles were found to have a substantial role in developing and opposing other surrogate markers of ACL loading. Similarly, both knee-spanning and non-knee-spanning muscles were found to play a substantial role in compressive loading of the medial and lateral tibiofemoral compartments. Additionally this program of research developed a greater understanding of the contribution of the hamstrings, and other lower-limb muscles, to the coordination of a sidestep cut. The hamstrings played a key role in maintaining anterior propulsion during early stance, although the majority of the demands of sidestep cutting (bodyweight support, propulsion and redirection) were provided by the vasti, gluteus maximus, soleus and gastrocnemius. The data from this program of research will inform ACL injury rehabilitation and injury prevention practices which should consider not only targeting the hamstrings but also other non-knee-spanning muscles for loading and unloading the knee during sidestep cutting. Additionally, this thesis provides data that may inform strategies aiming to modulate muscle forces to alter tibiofemoral compressive forces, which may be involved in ACL injury and concomitant meniscal and articular cartilage injury. Finally, this thesis provides further data informing how these muscles contribute to the performance of sidestep cut, in order to achieve optimal balance between performance and injury risk considerations. The findings from this thesis also dictates that future investigations that aim to examine the link between prior HSI and increased knee joint loading need to broaden the scope of such work to consider the influence of other lower-limb muscles as well as multi-planar movements

Trends in Australian knee injury rates : An epidemiological analysis of 228,344 knee injuries over 20 years

Background Acute knee injuries are a key predisposing risk factor for knee osteoarthritis. Public health interventions require in-depth epidemiological evidence to determine which knee injuries are problematic in critical age and sex demographics. Methods Descriptive epidemiological analysis of longitudinal data on knee injuries (July 1998 – June 2018) from the National Hospital Morbidity Database in Australia were studied. The main outcomes where the population-related knee injury frequency, incidence per 100,000 and annual growth rate (%) over the 20-year observation period. Age-group and sex differences were also studied to determine demographic-specific trends. Findings 228,344 knee injuries were diagnosed over the 20-year analysis period. Significantly rising annual incidences were observed for total knee injuries, anterior cruciate ligament (ACL) injuries and knee contusions in males and females. Posterior cruciate ligament (PCL) injuries and knee dislocations were also rising in females, but not males. Greater annual growth rates were observed for females compared to males for total knee injuries, knee contusions, PCL injuries and knee dislocations. Demographic analysis revealed that the highest annual growth rate in injury incidence (10.4%) was observed for ACL injuries in females aged 5–14 years old. Interpretation Increasing annual incidence of knee injuries was observed over the 20-year period. Males have a higher incidence of knee injury per capita than females, but the gap appears to have narrowed over the 20-year analysis period. Younger Australians show a precipitous rise in the annual number of ACL injuries, particularly for females aged 5–14 years. These trends warrant urgent intervention. Funding None

Muscle force contributions to anterior cruciate ligament loading

Anterior cruciate ligament (ACL) injuries are one of the most common knee pathologies sustained during athletic participation and are characterised by long convalescence periods and associated financial burden. Muscles have the ability to increase or decrease the mechanical loads on the ACL, and thus are viable targets for preventative interventions. However, the relationship between muscle forces and ACL loading has been investigated by many different studies, often with differing methods and conclusions. Subsequently, this review aimed to summarise the evidence of the relationship between muscle force and ACL loading. A range of studies were found that investigated muscle and ACL loading during controlled knee flexion, as well as a range of weightbearing tasks such as walking, lunging, sidestep cutting, landing and jumping. The quadriceps and the gastrocnemius were found to increase load on the ACL by inducing anterior shear forces at the tibia, particularly when the knee is extended. The hamstrings and soleus appeared to unload the ACL by generating posterior tibial shear force; however, for the hamstrings, this effect was contingent on the knee being flexed greater than ~ 20° to 30°. The gluteus medius was consistently shown to oppose the knee valgus moment (thus unloading the ACL) to a magnitude greater than any other muscle. Very little evidence was found for other muscle groups with respect to their contribution to the loading or unloading of the ACL. It is recommended that interventions aiming to reduce the risk of ACL injury consider specifically targeting the function of the hamstrings, soleus and gluteus medius

Architectural changes of the biceps femoris long head after concentric or eccentric training

Purpose: To determine i) the architectural adaptations of the biceps femoris long head (BFlf) following concentric or eccentric strength training interventions; ii) the time course of adaptation during training and detraining. Methods: Participants in this randomized controlled trial (control [n=28], concentric training group [n=14], eccentric training group [n=14], males) completed a 4-week control period, followed by 6 weeks of either concentric- or eccentric-only knee flexor training on an isokinetic dynamometer and finished with 28 days of detraining. Architectural characteristics of BFlf were assessed at rest and during graded isometric contractions utilizing two-dimensional ultrasonography at 28 days pre-baseline, baseline, days 14, 21 and 42 of the intervention and then again following 28 days of detraining. Results: BFlf fascicle length was significantly longer in the eccentric training group (p < 0.05, d range: 2.65 to 2.98) and shorter in the concentric training group (p < 0.05, d range: -1.62 to -0.96) after 42 days of training compared to baseline at all isometric contraction intensities. Following the 28-day detraining period, BFlf fascicle length was significantly reduced in the eccentric training group at all contraction intensities compared to the end of the intervention (p < 0.05, d range: -1.73 to -1.55). There was no significant change in fascicle length of the concentric training group following the detraining period. Conclusions: These results provide evidence that short term resistance training can lead to architectural alterations in the BFlf. In addition, the eccentric training-induced lengthening of BFlf fascicle length was reversed and returned to baseline values following 28 days of detraining. The contraction mode specific adaptations in this study may have implications for injury prevention and rehabilitation

Experimental Investigation On Nanoparticles Suspended Liquid (NSL) As The Heat Transfer Fluid (HTF) For Solar Evacuated Tube Collector

This study investigates the thermal performance of a solar evacuated tube collector (SETC) using nanoparticles suspended liquid (NSL) as the heat transfer fluid (HTF). The NSL is composed of water with different concentration of TiO2, CuO, Cr2O3, TiO2+CuO+ Cr2O3 NSL With average size of ~25 nm. The experimental results show that the use of NSL increase the thermal performance of the SETC to be about 2% higher than that of the SETC without NSL. The enhancement in the thermal performance is mainly attributed to the higher thermal conductivity and specific heat capacity of the NSL. In addition, the effects of NSL concentration, flow rate and temperature on the thermal performance of the SETC with NSL were also studied. It was observed that the thermal performance of the SETC with NSL increases with increasing NSL concentration and flow rate but decreases with rise in the temperature. The results of this study can be used to optimize the design of solar evacuated tube collectors using NSL as the HTF for better thermal performance

Explosive Hamstrings Strength Asymmetry Persists Despite Maximal Hamstring Strength Recovery Following Anterior Cruciate Ligament Reconstruction Using Hamstring Tendon Autografts

PURPOSE: To investigate the differences in maximal (isometric and concentric peak torque) and explosive (rate of torque development (RTD)) hamstring and quadriceps strength symmetry between males and females during early- and late-phase rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring tendon (HT) autografts and to determine the interaction of time and sex on maximal and explosive strength symmetry. METHODS: A total of 38 female and 51 male participants were assessed during early (3–6 months post-operative) and late (7–12 months post-operative) phases of rehabilitation following ACLR. Maximal (concentric and isometric peak torque) and explosive (isometric RTD) hamstring and quadriceps strength were assessed and presented as limb symmetry index (LSI). RESULTS: Maximal concentric hamstrings asymmetry (Early: 86 ± 14; Late 92 ± 13; p = 0.005) as well as maximal concentric (Early, 73 ± 15; Late 91 ± 12; p < 0.001) and explosive (Early: 82 ± 30; Late: 92 ± 25; p = 0.03) quadriceps asymmetry decreased from early to late rehabilitation. However, there were no significant changes in maximal isometric quadriceps strength and explosive isometric hamstring strength in the same time period. Females had a larger asymmetry in maximal concentric (Females: 75 ± 17; Males: 81 ± 15; p = 0.001) and explosive (Females: 81 ± 32; Males: 89 ± 25; p = 0.01) quadriceps strength than males throughout rehabilitation. There were no sex differences in maximal and explosive hamstring strength. There were no sex by time interactions for any variables. CONCLUSION: Explosive hamstring strength asymmetry did not improve despite recovery of maximal hamstring strength during rehabilitation following ACLR with HT autografts. While sex did not influence strength recovery, females had larger maximal and explosive quadriceps strength asymmetry compared to males throughout rehabilitation following ACLR. LEVEL OF EVIDENCE: Level III SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00167-022-07096-y

Session availability as a result of prior injury impacts the risk of subsequent injury in elite male Australian footballers

Prior injury is a commonly identified risk factor for subsequent injury. However, a binary approach to classifying prior injury (i.e., yes/no) is commonly implemented and may constrain scientific findings, as it is possible that variations in the amount of time lost due to an injury will impact subsequent injury risk to differing degrees. Accordingly, this study investigated whether session availability, a surrogate marker of prior injury, influenced the risk of subsequent non-contact lower limb injury in Australian footballers. Data were collected from 62 male elite Australian footballers throughout the 2015, 2016, and 2017 Australian Football League seasons. Each athlete’s participation status (i.e., full or missed/modified) and any injuries that occurred during training sessions/matches were recorded. As the focus of the current study was prior injury, any training sessions/matches that were missed due to reasons other than an injury (e.g., load management, illness and personal reasons) were removed from the data prior to all analyses. For every Monday during the in-season periods, session availability (%) in the prior 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, and 84 days was determined as the number of training sessions/matches fully completed (injury free) relative to the number of training sessions/matches possible in each window. Each variable was modeled using logistic regression to determine its impact on subsequent injury risk. Throughout the study period, 173 non-contact lower limb injuries that resulted in at least one missed/modified training session or match during the in-season periods occurred. Greater availability in the prior 7 days increased injury probabilities by up to 4.4%. The impact of session availability on subsequent injury risk diminished with expanding windows (i.e., availability in the prior 14 days through to the prior 84 days). Lesser availability in the prior 84 days increased injury probabilities by up to 14.1%, only when coupled with greater availability in the prior 7 days. Session availability may provide an informative marker of the impact of prior injury on subsequent injury risk and can be used by coaches and clinicians to guide the progression of training, particularly for athletes that are returning from long periods of injury

Putting the squeeze on compression garments: current evidence and recommendations for future research: a systematic scoping review

Background: Compression garments are regularly worn during exercise to improve physical performance, mitigate fatigue responses, and enhance recovery. However, evidence for their efficacy is varied and the methodological approaches and outcome measures used within the scientific literature are diverse. Objectives: The aim of this scoping review is to provide a comprehensive overview of the effects of compression garments on commonly assessed outcome measures in response to exercise, including: performance, biomechanical, neuromuscular, cardiovascular, cardiorespiratory, muscle damage, thermoregulatory, and perceptual responses. Methods: A systematic search of electronic databases (PubMed, SPORTDiscus, Web of Science and CINAHL Complete) was performed from the earliest record to 27 December, 2020. Results: In total, 183 studies were identified for qualitative analysis with the following breakdown: performance and muscle function outcomes: 115 studies (63%), biomechanical and neuromuscular: 59 (32%), blood and saliva markers: 85 (46%), cardiovascular: 76 (42%), cardiorespiratory: 39 (21%), thermoregulatory: 19 (10%) and perceptual: 98 (54%). Approximately 85% (n = 156) of studies were published between 2010 and 2020. Conclusions: Evidence is equivocal as to whether garments improve physical performance, with little evidence supporting improvements in kinetic or kinematic outcomes. Compression likely reduces muscle oscillatory properties and has a positive effect on sensorimotor systems. Findings suggest potential increases in arterial blood flow; however, it is unlikely that compression garments meaningfully change metabolic responses, blood pressure, heart rate, and cardiorespiratory measures. Compression garments increase localised skin temperature and may reduce perceptions of muscle soreness and pain following exercise; however, rating of perceived exertion during exercise is likely unchanged. It is unlikely that compression garments negatively influence exercise-related outcomes. Future research should assess wearer belief in compression garments, report pressure ranges at multiple sites as well as garment material, and finally examine individual responses and varying compression coverage areas

The development of a HAMstring InjuRy (HAMIR) index to mitigate injury risk through innovative imaging, biomechanics, and data analytics : Protocol for an observational cohort study

Background The etiology of hamstring strain injury (HSI) in American football is multi-factorial and understanding these risk factors is paramount to developing predictive models and guiding prevention and rehabilitation strategies. Many player-games are lost due to the lack of a clear understanding of risk factors and the absence of effective methods to minimize re-injury. This paper describes the protocol that will be followed to develop the HAMstring InjuRy (HAMIR) index risk prediction models for HSI and re-injury based on morphological, architectural, biomechanical and clinical factors in National Collegiate Athletic Association Division I collegiate football players. Methods A 3-year, prospective study will be conducted involving collegiate football student-athletes at four institutions. Enrolled participants will complete preseason assessments of eccentric hamstring strength, on-field sprinting biomechanics and muscle–tendon volumes using magnetic-resonance imaging (MRI). Athletic trainers will monitor injuries and exposure for the duration of the study. Participants who sustain an HSI will undergo a clinical assessment at the time of injury along with MRI examinations. Following completion of structured rehabilitation and return to unrestricted sport participation, clinical assessments, MRI examinations and sprinting biomechanics will be repeated. Injury recurrence will be monitored through a 6-month follow-up period. HAMIR index prediction models for index HSI injury and re-injury will be constructed. Discussion The most appropriate strategies for reducing risk of HSI are likely multi-factorial and depend on risk factors unique to each athlete. This study will be the largest-of-its-kind (1200 player-years) to gather detailed information on index and recurrent HSI, and will be the first study to simultaneously investigate the effect of morphological, biomechanical and clinical variables on risk of HSI in collegiate football athletes. The quantitative HAMIR index will be formulated to identify an athlete’s propensity for HSI, and more importantly, identify targets for injury mitigation, thereby reducing the global burden of HSI in high-level American football players. Trial Registration The trial is prospectively registered on ClinicalTrials.gov (NCT05343052; April 22, 2022)

Systematically searching and reviewing the literature

Reviewing the literature is a critical step in the research process. Whilst there are many different types of review articles the purpose of this chapter is to provide a brief reference guide for those who are attempting a systematic literature review for the first time. This includes information around registering your systematic review, developing eligibility criteria, formulating a search strategy, approaches to data management, guidance for quality and risk of bias assessment and data (meta-)analysis. This chapter should help to set individuals on their way to conducting a rigorous systematic review