EXPLORING THE POTENTIAL EFFECTS OF STRENGTH TRAINING ON RUNNING ECONOMY: A SIMULATION STUDY

Strength training can improve running economy (RE) and performance in distance runners. This study investigated the effect of potential adaptations stemming from strength training on RE using simulation. Muscle-tendon unit (MTU) properties (muscle strength and mass, pennation angle, tendon stiffness, fibre composition) of muscle groups were altered within muscle-driven simulations of running at 4.5 and 6.5 m·s-1. Outputs from the muscle-driven simulations were input to an energetics model to determine whole-body metabolic power. Alterations to MTU properties resulted in variable changes (range = 1.4% decrement – 8.9% improvement in RE) to whole-body metabolic power and RE. The findings highlight potential targets for strength training programs aiming to improve RE in distance runners

Altered movement patterns but not muscle recruitment in moderately trained triathletes during running after cycling

Previous studies have shown that cycling can directly influence neuromuscular control during subsequent running in some highly trained triathletes, despite these triathletes\u27 years of practice of the cycle-run transition. The aim of this study was to determine whether cycling has the same direct influence on neuromuscular control during running in moderately trained triathletes. Fifteen moderately trained triathletes participated. Kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Muscle recruitment was different between control and transition runs in only one of 15 triathletes (&lt;7%). Changes in joint position (mean difference of 3&deg;) were evident in five triathletes, which persisted beyond 5 min of running in one triathlete. Our findings suggest that some moderately trained triathletes have difficulty reproducing their pre-cycling movement patterns for running initially after cycling, but cycling appears to have little influence on running muscle recruitment in moderately trained triathletes. <br /

LOWER BODY MUSCULOTENDON UNIT FUNCTION DURING BOUNDING, HURDLE JUMPING AND RUNNING

To facilitate exercise prescription, this study compared the function of six lower limb musculotendon units during plyometric exercises with running. Fourteen distance runners performed overground running (3.89 m/s), bounding, and hurdle jumps. Computational simulations were used to compare musculotendon unit function, peak powers, and total work. Compared to running, the hurdle jumps had greater gluteus maximus peak power absorption (12.1%; SMD 0.65), and gluteus maximus (15.7%; SMD 0.51) and soleus (16.5%; SMD 0.92) total negative work. Hurdle jumps may be an appropriate exercise when higher eccentric loads of the gluteus maximus and soleus are required. Compared to running, bounding had increased gastrocnemius total negative work (63.8%; SMD 0.81) and may be suitable when eccentric overload of the gastrocnemius is desired

Anterior cruciate ligament injuries in Australian football: Should women and girls be playing? You\u27re asking the wrong question

Anterior cruciate ligament (ACL) injuries have been a rising concern in the early years of the women\u27s Australian Football League (AFLW), eliciting headlines of a â € knee crisis\u27 surrounding the league. There has been a focus on female biology as the primary factor driving the high rate of ACL injuries in the AFLW. Emphasising Australian football (AF) as being dangerous predominantly due to female biology may be misrepresenting a root cause of the ACL injury problem, perpetuating gender stereotypes that can restrict physical development and participation of women and girls in the sport. We propose that an approach addressing environmental and sociocultural factors, along with biological determinants, is required to truly challenge the ACL injury problem in the AFLW. Sports science and medicine must therefore strive to understand the whole system of women in AF, and question how to address inequities for the benefit of the athletes. © © Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ

Anterior cruciate ligament injuries in Australian football: Should women and girls be playing? You\u27re asking the wrong question

Anterior cruciate ligament (ACL) injuries have been a rising concern in the early years of the women\u27s Australian Football League (AFLW), eliciting headlines of a â € knee crisis\u27 surrounding the league. There has been a focus on female biology as the primary factor driving the high rate of ACL injuries in the AFLW. Emphasising Australian football (AF) as being dangerous predominantly due to female biology may be misrepresenting a root cause of the ACL injury problem, perpetuating gender stereotypes that can restrict physical development and participation of women and girls in the sport. We propose that an approach addressing environmental and sociocultural factors, along with biological determinants, is required to truly challenge the ACL injury problem in the AFLW. Sports science and medicine must therefore strive to understand the whole system of women in AF, and question how to address inequities for the benefit of the athletes. © © Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ

THE INFLUENCE OF MUSCULAR ACTIVATION PROFILES ON LOWER LIMB BIOMECHANICS DURING A SPORT-SPECIFIC LANDING TASK

The purpose of this study was to identify the muscular activation profiles utilised by female athletes during a sport-specific landing task, and examine the effects of varying profiles on biomechanical anterior cruciate ligament (ACL) injury risk factors. Muscular activation profiles were identified from electromyography data using a combination of principal component and cluster analysis methods, with the neuromuscular and biomechanical characteristics of profiles compared. Various muscular activation characteristics contributed to the presence of lower limb biomechanical patterns consistent with ACL injury risk factors. Reduction of ACL injury risk may be achieved by targeting these muscular activation characteristics via neuromuscular training programs

Neuromuscular control and running economy is preserved in elite international triathletes after cycling

Running is the most important discipline for Olympic triathlon success. However, cycling impairs running muscle recruitment and performance in some highly trained triathletes; though it is not known if this occurs in elite international triathletes. The purpose of this study was to investigate the effect of cycling in two different protocols on running economy and neuromuscular control in elite international triathletes. Muscle recruitment and sagittal plane joint angles of the left lower extremity and running economy were compared between control (no preceding cycle) and transition (preceded by cycling) runs for two different cycle protocols (20-minute low-intensity and 50-minute high-intensity cycles) in seven elite international triathletes. Muscle recruitment and joint angles were not different between control and transition runs for either cycle protocols. Running economy was also not different between control and transition runs for the ow-intensity (62.4 ^ 4.5 vs. 62.1 ^ 4.0 ml/min/kg, p . 0.05) and high-intensity (63.4 ^ 3.5 vs. 63.3 ^ 4.3 ml/min/kg, p . 0.05) cycle protocols. The results of this study demonstrate that both low- and high-intensity cycles do not adversely influence neuromuscular control and running economy in elite international triathletes.<br /

Efficacy of stability-based training with visualisation in people with chronic ankle instability

Background Chronic ankle instability (CAI) is associated with recurrent ankle sprains, mechanical laxity and/or perceived instability. Stability-based rehabilitative training has been found to prevent further injury, however poor programme compliance can hinder the programme’s effectiveness. Virtual reality (VR) systems have been shown to provide a stimulating and motivational environment that may be more conducive to rehabilitation adherence. An emerging technique, visualisation, is the connection of biomechanical analysis and VR. Visualisation produces real-time feedback, by accurately monitoring movement and progress, using VR to create a diverse, challenging, and controllable environment, representative of real-world situations. Objective The aim of this study was to determine the feasibility of incorporating visualisation into stability training for people with chronic ankle instability. Specifically, the effect of visualisation on performance of the Star Excursion Balance Test (SEBT), as well as participant’s enjoyment of the experience. Design and Methods Individuals with CAI were randomly allocated to the 4-week stability-based training programme with visualisation (VIS), or without (NO-VIS). Balance exercises were based on standard practice, with adaptations for visualisation. Participants completed the SEBT and Cumberland Ankle Instability Tool (CAIT) prior to, and after training. Participants recorded enjoyment of training using the Physical Activity Enjoyment Scale (PACES-8). The Strathclyde Cluster Model and pointer calibration were applied to all participants. Movement was tracked using Vicon Tracker (Vicon, Oxford, UK), with testing controlled and recorded using D-Flow (Motek Medical, Amsterdam, The Netherlands). Effect size (d) was calculated and interpreted using Hopkin’s recommendations. Results Of 17 participants (Vis=10,No-Vis=7), there were 2 drop outs (Vis=1,No-Vis=1). No adverse events were reported and participant drop-out was due to injury unrelated to the study. There were no between-group differences in population demographics and pre-training CAIT scores (p⩾0.2). Following training there was a non-significant but small effect (d=0.6,p=0.3) favouring the NO-VIS group for an increase in CAIT score. There was a non-significant but moderate effect (d=1,p=0.20) favouring the VIS group for an increase in average reach distance on the SEBT. There was a non-significant but large effect (d=1.4,p=0.16) for higher enjoyment of training in the VIS group. Conclusions Results of this study support the feasibility and safety of stability training with visualisation in those with CAI. Observations of a more enjoyable experience, alongside improved postural control suggest visualisation may enhance stability-based training. Implications of this will be discussed, along with the practicalities and logistics of running such programmes

THE INFLUENCE OF SPEED ON PATELLOFEMORAL JOINT KINETICS IN RECREATIONAL RUNNERS

This study aimed to determine the influence of running speed on patellofemoral joint (PFJ) kinetics. Twenty recreational runners ran on an instrumented treadmill at four running speeds with simultaneous 3D motion capture. A musculoskeletal model derived peak and cumulative (per 1km of continuous running) PFJ force and stress for each speed. Peak PFJ force and stress significantly increased with faster speeds. In contrast, cumulative PFJ measures decreased with faster speeds. Running at faster speeds increases the magnitude of peak PFJ kinetics but conversely results in less accumulated force over a set distance. Clinicians and coaches should be aware of the relatively high PFJ cumulative force and stress associated with slow running (~2.5 m/s) and consider moderate-speed interval running as part of overuse knee injury prevention and management plans

Measurement error associated with gait cycle selection in treadmill running at various speeds

A common approach in the biomechanical analysis of running technique is to average data from several gait cycles to compute a ‘representative mean.’ However, the impact of the quantity and selection of gait cycles on biomechanical measures is not well understood. We examined the effects of gait cycle selection on kinematic data by: (i) comparing representative means calculated from varying numbers of gait cycles to ‘global’ means from the entire capture period; and (ii) comparing representative means from varying numbers of gait cycles sampled from different parts of the capture period. We used a public dataset (n = 28) of lower limb kinematics captured during a 30-second period of treadmill running at three speeds (2.5 m s−1, 3.5 m s−1 and 4.5 m s−1). ‘Ground truth’ values were determined by averaging data across all collected strides and compared to representative means calculated from random samples (1,000 samples) of n (range = 5–30) consecutive gait cycles. We also compared representative means calculated from n (range = 5–15) consecutive gait cycles randomly sampled (1,000 samples) from within the same data capture period. The mean, variance and range of the absolute error of the representative mean compared to the ‘ground truth’ mean progressively reduced across all speeds as the number of gait cycles used increased. Similar magnitudes of ‘error’ were observed between the 2.5 m s−1 and 3.5 m s−1 speeds at comparable gait cycle numbers —where the maximum errors were < 1.5 degrees even with a small number of gait cycles (i.e., 5–10). At the 4.5 m s−1 speed, maximum errors typically exceeded 2–4 degrees when a lower number of gait cycles were used. Subsequently, a higher number of gait cycles (i.e., 25–30) was required to achieve low errors (i.e., 1–2 degrees) at the 4.5 m s−1 speed. The mean, variance and range of absolute error of representative means calculated from different parts of the capture period was consistent irrespective of the number of gait cycles used. The error between representative means was low (i.e., < 1.5 degrees) and consistent across the different number of gait cycles at the 2.5 m s−1 and 3.5 m s−1 speeds, and consistent but larger (i.e., up to 2–4 degrees) at the 4.5 m s−1 speed. Our findings suggest that selecting as many gait cycles as possible from a treadmill running bout will minimise potential ‘error.’ Analysing a small sample (i.e., 5–10 cycles) will typically result in minimal ‘error’ (i.e., < 2 degrees), particularly at lower speeds (i.e., 2.5 m s−1 and 3.5 m s−1). Researchers and clinicians should consider the balance between practicalities of collecting and analysing a smaller number of gait cycles against the potential ‘error’ when determining their methodological approach. Irrespective of the number of gait cycles used, we recommend that the potential ‘error’ introduced by the choice of gait cycle number be considered when interpreting the magnitude of effects in treadmill-based running studies