Reliability of recovery heart rate variability measurements as part of the Lamberts Submaximal Cycle Test and the relationship with training status in trained to elite cyclists.

PURPOSE: To determine if post-exercise heart rate variability, in the form of logged transformed root mean square of successive differences of the R-R intervals (LnRMSSD) can be measured reliably during the recovery from a submaximal cycle test and what the relationship of LnRMSSD is with training status of the cyclists. METHODS: Fourteen male cyclists participated in the reliability part for the study, which included performing six Lamberts Submaximal Cycle Test (LSCT), during which recovery LnRMSSD was measured over 30 s (LnRMSSD30 s), 60 s LnRMSSD60 s)and 90 s LnRMSSD90 s). In addition, fifty male and twenty female cyclists completed a peak power output (PPO) test (including VO2peak) and 40 km time trial (40 km TT) before which they performed the LSCT as a standardized warm-up. Relationships between the LnRMSSD and PPO, VO2peak and 40 km TT time were studied. RESULTS: Due to the design of the LSCT, submaximal heart and breathing rate were similar at the end of stage 3 of the LSCT, as well as during the recovery periods. The highest reliability was found in LnRMSSD60 s (ICC: 0.97) with a typical error of the measurement (TEM: 5.8%). In line with this the strongest correlations were found between LnRMSSD60 s and PPO (r = 0.93[male]; 0.85[female]), VO2peak (r = 0.71[male]; 0.63[female];) and 40 km TT (r = - 0.83[male]; - 0.63[female]). CONCLUSIONS: LnRMSSD60 s can be measured reliably after the LSCT and can predict PPO, VO2peak and 40 km TT performance well in trained-to-elite cyclists. These findings suggest that recovery LnRMSSD can potentially play an important role in monitoring and fine-tuning training prescriptions in trained-to-elite cyclists.

Assessing spring-mass similarity in elite and recreational runners.

The dynamic complexity and individualization of running biomechanics has challenged the development of objective and comparative gait measures. Here, we present and explore several novel biomechanical metrics for running that are informed by a canonical inter-species gait template-the spring-mass model. The measures assess running mechanics systemically against the template via quantifying characteristics of a runner's kinetics relative to the energy-conserving elastic system-i.e., their "spring-mass similarity". Applying these metrics in a retrospective cohort investigation, we studied the overground kinetics of two heterogenous populations of runners in two footwear conditions: elite and recreational athletes in shod and barefoot conditions. Across all measures and within foot strike types, the elite runners exhibited mechanics that were more similar to those of the ideally elastic spring-mass template. The elite runners had more symmetric bounces, less discrepancy (i.e., greater coordination) between horizontal and vertical kinetic changes, and better fit to a spring-mass vertical ground reaction force time series. Barefoot running elicited greater kinetic coordination in the recreational runners. At a faster speed, the elites further improved their similarity to the template. Overall, the more economical elite group exhibited greater likeness to the linearly elastic, energy-conserving spring-mass system than their recreational counterparts. This study introduces novel biomechanical measures related to performance in distance running. More broadly, it provides new, approachable metrics for systemic quantification of gait biomechanics in runners across all demographics. These metrics may be applied to assess a runner's global biomechanical response to a variety of interventions, including training adaptations, rehabilitation programs, and footwear conditions.

Overhead throwing biomechanics in cricketers: The effect of a run-up approach.

Overhead throwing by cricketers when fielding with different approaches has been described using two-dimensional analysis. Currently, the three-dimensional kinematic and kinetic characteristics of an overhead throw performed by cricketers following a run-up are unknown. Fifteen South African cricketers performed six overhead throws, from a stationary position and with a run-up over 15-20 m prior to fielding a ball, respectively. Kinematic data and ground reaction forces were collected throughout the throwing trials. Joint kinetics were calculated using inverse dynamics. An independent t-test or Mann-Whitney U-test was used to determine joint kinetic differences between throwing approaches. Differences between the kinematic waveforms for stationary and run-up throwing approaches were assessed using one-dimensional statistical parametric mapping ANOVA (P < 0.05). The shoulder, elbow and thoraco-lumbar joints displayed similar kinematics between throwing approaches. The run-up approach displayed increased hip flexion between 0-34% and 57-100% (F(1, 28) = 6.726; P = 0.01) of the throwing cycle; and lumbo-pelvic flexion between 57 and 65% (F(1, 28) = 6.823; P = 0.02) of the throwing cycle; greater shoulder compression (F(1, 28) = 1.036; P = 0.02) and posterior force (F(1, 28) = 1.052; P = 0.009) at maximum external rotation; yet less superior shoulder force (F(1, 28) = 1.744; P = 0.005) and elbow compression (F(1, 28) = 4.331; P = 0.03), superior (F(1, 28) = 1.212; P = 0.002) and medial (F(1, 28) = 1.370; P = 0.03) elbow forces at ball release, when compared to a stationary position. Cricketers maintain similar upper limb kinematics between overhead throwing approaches. However, throwing with a run-up approximately doubles the forces exerted on the shoulder at maximum external rotation, which is most likely caused by the greater dominant hip and lumbo-pelvic flexion noted. This may amplify the potential risk for shoulder injury when throwing.HighlightsThrowing arm motion is similar irrespective of the approach used by cricketers to throw.Throwing with a run-up produced increased angles of lumbo-pelvic and dominant hip flexion in various phases of the throwing cycle.Throwing with a run-up resulted in greater shoulder compression and posterior force at maximum external rotation.

The association between gird and overhead throwing biomechanics in cricket.

The development of GIRD is a well-documented adaptation associated with repetitive overhead throwing in numerous sports. In occurrence with total rotational range of motion deficit, GIRD is considered pathological and increases shoulder injury risk. While cricketers demonstrate these deficits in rotational range; the association between GIRD and overhead throwing has yet to be explored. Therefore, the aim of this study was to determine the relationship between GIRD and overhead throwing biomechanics in cricketers. Passive shoulder rotational range of motion was measured in 15 cricketers (elite = 8, amateur = 7). Kinetic and kinematic data were obtained during overhead throws from a stationary and run-up approach. Linear regression was used to determine potential relationships between GIRD and discrete shoulder kinetics for both throwing approaches. One-dimensional statistical parametric mapping regression was conducted to assess relationships between GIRD and throwing kinematics. When throwing overhead from a stationary position, GIRD was associated with reduced hip abduction during the preparatory arc (p = 0.002); superior shoulder (p = 0.003) and elbow compressive (p = 0.009) forces, at cocking. In addition, GIRD was associated with increased posterior shoulder force during arm deceleration for both stationary (p = 0.013) and run-up approaches (p = 0.03) to overhead throwing. Cricketers with GIRD utilise a shorter stride, creating early pelvic rotation and a slow throwing arm with an associated reduction in forces about the shoulder and elbow at cocking, when throwing from a stationary position. Further, overload of the posterior shoulder occurs during arm deceleration, irrespective of throwing approach. These findings highlight potential shoulder injury risk.

Overhead throwing in cricketers: A biomechanical description and playing level considerations.

This study aimed to describe stationary overhead throwing biomechanics in South African cricketers, considering playing level, and relative to baseball. Kinematics and ground reaction forces were collected during throwing trials. Inverse dynamics was used to calculate joint kinetics. Inter-subject variability was calculated using the coefficient of variance. A one-dimensional statistical parametric mapping ANOVA was conducted to assess differences between the kinematic waveforms in elite and amateur cricketers (p < 0.05). Fifteen cricketers (elite = 8; amateur = 7) participated in this study. The basic parameters of a cricketer's throwing action are described. Substantial inter-subject variability was noted for all variables, except lumbopelvic movement. Cricketers presented with 74.9 ± 27.3° glenohumeral external rotation and 94.8 ± 23.7° elbow flexion, at maximum external rotation (MER). Amateur cricketers displayed decreased elbow flexion range of motion between 2-14% of the throwing cycle (F = 9.365;p = 0.01); greater shoulder (121.0vs85.9 N; F = 0.36,p = 0.021) and elbow compression (105.6vs72.8 N;F = 0.007,p = 0.043), and superior shoulder force (203.1vs115.5 N;F = 2.43,p = 0.022) at MER, when compared with elite cricketers. Cricketers display similarities to baseball pitchers when throwing overhead from a stationary position. The "preparatory arc" utilised is different to the wind-up noted for baseball. The forces exerted on the shoulder and elbow, in amateur cricketers specifically, are substantially greater at MER and may indicate the potential risk for injury.

Heat dissipating upper body compression garment: Thermoregulatory, cardiovascular, and perceptual responses.

PURPOSE: The aim of the present study was to determine the effects of an upper body compression garment (UBCG) on thermoregulatory responses during cycling in a controlled laboratory thermoneutral environment (~23°C). A secondary aim was to determine the cardiovascular and perceptual responses when wearing the garment. METHODS: Sixteen untrained participants (age: 21.3 ± 5.7 years; peak oxygen consumption (VO2peak): 50.88 ± 8.00 mL/min/kg; mean ± SD) performed 2 cycling trials in a thermoneutral environment (~23°C) wearing either UBCG or control (Con) garment. Testing consisted of a 5-min rest on a cycle ergometer, followed by 4 bouts of cycling for 14-min at ~50%VO2peak, with 1-min rest between each bout. At the end of these bouts there was 10-min of passive recovery. During the entire protocol rectal temperature (T rec), skin temperature (T skin), mean body temperature (T body), and heat storage (HS) were measured. Heart rate (HR), VO2, pH, hematocrit (Hct), plasma electrolytes, weight loss (W loss), and perceptual responses were also measured. RESULTS: There were no significant differences between garments for T skin, HS, HR, VO2, pH, Hct, plasma electrolyte concentration, W loss, and perceptual responses during the trial. T rec did not differ between garment conditions during rest, exercise, or recovery although a greater reduction in T rec wearing UBCG (p = 0.01) was observed during recovery. Lower T body during recovery was found when wearing UBCG (36.82°C ± 0.30°C vs. 36.99°C ± 0.24°C). CONCLUSION: Wearing a UBCG did not benefit thermoregulatory, cardiovascular, and perceptual responses during exercise although it was found to lower Tbody during recovery, which suggests that it could be used as a recovery tool after exercise.

Gait Pattern of Adults with Cerebral Palsy and Spastic Diplegia More Than 15 Years after Being Treated with an Interval Surgery Approach: Implications for Low-Resource Settings.

BACKGROUND: Single-event multilevel surgery (SEMLS) approach is regarded as the golden standard in developed countries to improve gait and functional mobility in children with cerebral palsy (CP). However, this approach is not always feasible in developing countries. Therefore, orthopedic surgery based on an interval surgery approach (ISA) is still commonly used in developing countries, although little is known about the long term outcomes of an ISA. Therefore, the aim of this study was to describe the gait patterns of adults with CP, who have been treated with ISA, which started more than 15 years ago. MATERIALS AND METHODS: Thirty adults with CP and spastic diplegia, who received ISA treatment 21.6-33.7 years ago, were recruited for this study and participated in three-dimensional gait analysis. Twenty kinematic and nondimensional temporal-distance parameters were captured, while the overall gait deviation index (GDI) was also calculated. Data of the adults with CP were compared to normative data of typically developing (TD) adults. RESULTS: Although all adults with CP were still ambulant, their gait parameters significantly differed from TD adults, with a lower GDI in the adults with CP. The CP gait patterns were characterized by excessive hip flexion and hip internal rotation as well as a stiff-knee gait. CONCLUSION: Although different to TD adults, the gait patterns observed in the adult with CP treated with ISA is in line with other studies. Gait patterns suggest that derotation osteotomies potentially could have improved the long term gait patterns. Although SEMLS might be the preferred treatment method, potentially resulting in better outcomes, ISA can also be used to treat children with CP in developing countries as India and South Africa, where a SEMLS approach is not always feasible.

Incidence and impact of time loss and non-time-loss shoulder injury in elite South African cricketers: A one-season, prospective cohort study.

OBJECTIVES: To determine the incidence, prevalence and impact of shoulder injury in elite South African cricketers. DESIGN: Prospective longitudinal cohort study. METHODS: One hundred and six senior national/franchise cricketers completed a pre-season Kerlan-Jobe Orthopaedic Clinic shoulder and elbow (KJOC) score. All injuries sustained during the 2016/2017 season were captured on an injury reporting system. Injuries were verified by the respective squad physiotherapist at the end of the season and post-season KJOC score was obtained from all the players. RESULTS: Eighteen percent (95% CI: 11-25%) of cricketers sustained a shoulder injury, at a rate of 0.19 injuries per player per year. Annual injury prevalence was 1.1%. Shoulder injury occurred primarily while throwing (58%). Fielding performance was maintained by adapting throwing technique (58%) or fielding position (21%). Thirty-two percent of shoulder injuries resulted in time lost to matches and/or training. A history of shoulder injury increased the risk of sustaining another injury by 1.91 times (95% CI: 1.73-2.15). Irrespective of injury, cricketers demonstrated consistently low pre- (78.5 ±â€¯15.6) and post-season (81.2 ±â€¯17.1) KJOC scores. Pre-season KJOC scores were significantly lower (r2 = 0.106, p = 0.001) in those cricketers with a history of shoulder injury. Cricketers who sustained a seasonal shoulder injury had significantly lower (r2 = 0.112, p < 0.001) post-season KJOC scores, indicating persistent shoulder pain or dysfunction. CONCLUSION: This is the first study to report both time- and non-time-loss shoulder injury in elite South African cricketers. All non-time-loss shoulder injuries compromised primary skill, while some resulted in changes to throwing technique and fielding position. Thus shoulder injury, whether it results in time loss or not, potentially impacts match performance.

The cricketer's shoulder: Not a classic throwing shoulder.

OBJECTIVES: To describe the musculoskeletal adaptations inherent to the cricketers' shoulder and determine potential predictors of shoulder injury in elite South African cricketers. DESIGN: Prospective longitudinal cohort study; SETTING: Non-clinical, at national cricket indoor training venues. PARTICIPANTS: One hundred and six elite cricketers, representing 82% of the South African national and franchise teams, consent. A total of 105 cricketers (27 ±â€¯4 years) were eligible for participation in this study. MAIN OUTCOME MEASURES: A pre-season shoulder screening battery including a shoulder function questionnaire, two ultrasonographic shoulder measurements and 14 musculoskeletal tests including pain provocation, range of motion, strength and flexibility was assessed. Non-contact dominant shoulder injuries were documented throughout the 2016/2017 season. RESULTS: The musculoskeletal profile of a cricketer's shoulder is described. 17% (95%CI: 9-24%) of cricketers sustained an injury during the 2016/2017 season. Two of the 17 screening tests predicted seasonal dominant shoulder injury (p < 0.05): a dominant supraspinatus tendon thickness ≥5.85 mm (sensitivity: 72%, specificity: 63%) and non-dominant pectoralis minor length ≤12.85 cm (sensitivity: 83%, specificity: 55%). CONCLUSION: The musculoskeletal adaptations inherent to cricketing shoulders are distinctly different to the classic "thrower's shoulder" described in baseball. A thickened dominant supraspinatus tendon and a shortened non-dominant pectoralis minor muscle are risk factors for developing shoulder injury in this group. This identifies the need to investigate preventative strategies (strengthening/flexibility) and throwing workload management in cricketers with shoulder injury.

Muscle Activation Patterns Correlate With Race Walking Economy in Elite Race Walkers: A Waveform Analysis.

PURPOSE: To analyze the association between muscle activation patterns on oxygen cost of transport in elite race walkers over the entire gait waveform. METHODS: A total of 21 Olympic race walkers performed overground walking trials at 14 km·h-1 where muscle activity of the gluteus maximus, adductor magnus, rectus femoris, biceps femoris, medial gastrocnemius, and tibialis anterior were recorded. Race walking economy was determined by performing an incremental treadmill test ending at 14 km·h-1. RESULTS: This study found that more-economical race walkers exhibit greater gluteus maximus (P = .022, r = .716), biceps femoris (P = .011, r = .801), and medial gastrocnemius (P = .041, r = .662) activation prior to initial contact and weight acceptance. In addition, during the propulsive and the early swing phase, race walkers with higher activation of the rectus femoris (P = .021, r = .798) exhibited better race walking economy. CONCLUSIONS: This study suggests that the neuromuscular system is optimally coordinated through varying muscle activation to reduce the metabolic demand of race walking. These findings highlight the importance of proximal posterior muscle activation during initial contact and hip-flexor activation during early swing phase, which are associated with efficient energy transfer. Practically, race walking coaches may find this information useful in the development of specific training strategies on technique.

Anthropometric characteristics of top-class Olympic race walkers.

BACKGROUND: Typical training programmes in elite race walkers involve high training volumes at low and moderate intensities, which have been reported to induce functional and structural adaptations at an anthropometric level. Since anthropometrical variables are closely related to movement efficiency and performance in endurance events, the aim of this study was to describe the anthropometric profile of world-class race walkers. METHODS: Twenty-nine world-class race walkers (21 men and 8 women) participated in this study. Anthropometric characteristics, including height, body mass, eight skinfolds, five girths and four bone breadths were measured. Body composition, somatotype, somatotype dispersion mean, somatotype attitudinal mean and height to weight ratio, as well as skinfolds extremity to trunk ratio were also calculated. RESULTS: Mean height, body mass and body mass index were 177.1±7.1 cm, 66.4±5.8 kg, and 21.2±1.3 kg·m2 for men and 165.6±4.5 cm, 53.6±3.7 kg, and 19.6±1.6 kg· m2 for women, respectively. Women presented greater body fat content (6.7±0.6 vs. 12.2±0.8%; very large effect), less muscle mass (65.6±4.6 vs. 61.6±2.6 kg; large effect), and were more endomorphic (large effect) than men. Men specialists in 20-km showed greater muscle mass (66.7±4.9 vs. 64.4±4.3 kg; moderate effect), and slightly higher skinfolds, girths, body fat content and were more mesomorphic than 50-km specialists (moderate effect). CONCLUSIONS: The present study expands the limited knowledge on the anthropometric characteristics and somatotype elements of elite top-class race walkers. The characterisation of the morphology of elite race walkers provides coaches a reference values to control the training development of the race walker, as well as providing reference values to improve talent identification.

Running Economy: Neuromuscular and Joint-Stiffness Contributions in Trained Runners.

CONTEXT: It is debated whether running biomechanics make good predictors of running economy, with little known about the neuromuscular and joint-stiffness contributions to economical running gait. PURPOSE: To understand the relationship between certain neuromuscular and spatiotemporal biomechanical factors associated with running economy. METHODS: Thirty trained runners performed a 6-min constant-speed running set at 3.3 m·s-1, where oxygen consumption was assessed. Overground running trials were also performed at 3.3 m·s-1 to assess kinematics, kinetics, and muscle activity. Spatiotemporal gait variables, joint stiffness, preactivation, and stance-phase muscle activity (gluteus medius, rectus femoris, biceps femoris, peroneus longus, tibialis anterior, and gastrocnemius lateralis and medius) were variables of specific interest and thus determined. In addition, preactivation and ground contact of agonist-antagonist coactivation were calculated. RESULTS: More economical runners presented with short ground-contact times (r = .639, P < .001) and greater stride frequencies (r = -.630, P < .001). Lower ankle and greater knee stiffness were associated with lower oxygen consumption (r = .527, P = .007 and r = .384, P = .043, respectively). Only  lateral gastrocnemius-tibialis anterior coactivation during stance was associated with lower oxygen cost of transport (r = .672, P < .0001). CONCLUSIONS: Greater muscle preactivation and biarticular muscle activity during stance were associated with more economical runners. Consequently, trained runners who exhibit greater neuromuscular activation prior to and during ground contact, in turn optimizing spatiotemporal variables and joint stiffness, will be the most economical runners.

Race walking gait and its influence on race walking economy in world-class race walkers.

AIM: The aim of this study was to determine the relationships between biomechanical parameters of the gait cycle and race walking economy in world-class Olympic race walkers. METHODS: Twenty-One world-class race walkers possessing the Olympic qualifying standard participated in this study. Participants completed an incremental race walking test starting at 10 km·h-1, where race walking economy (ml·kg-1·km-1) and spatiotemporal gait variables were analysed at different speeds. RESULTS: 20-km race walking performance was related to race walking economy, being the fastest race walkers those displaying reduced oxygen cost at a given speed (R = 0.760, p < 0.001). Longer ground contact times, shorter flight times, longer midstance sub-phase and shorter propulsive sub-phase during stance were related to a better race walking economy (moderate effect, p < 0.05). CONCLUSION: According to the results of this study, the fastest race walkers were more economi cal than the lesser performers. Similarly, shorter flight times are associated with a more efficient race walking economy. Coaches and race walkers should avoid modifying their race walking style by increasing flight times, as it may not only impair economy, but also lead to disqualification.

Bone health in elite Kenyan runners.

Impact loading in athletes participating in various sports has been positively associated with increased bone mineral density (BMD), but this has not been investigated in elite Kenyan runners. Body composition and site-specific BMD measures quantified with dual x-ray absorptiometry were measured in 15 elite male Kenyan runners and 23 apparently healthy South African males of different ethnicities. Training load and biomechanical variables associated with impact loading, such as joint stiffness, were determined in the elite Kenyan runners. Greater proximal femur (PF) BMD (g · cm-2) was higher (P = 0.001, ES = 1.24) in the elite Kenyan runners compared with the controls. Six of the 15 (40%) Kenyan runners exhibited lumbar spine (LS) Z-Scores below -2.0 SD, whereas this was not found in the apparently healthy controls. PFBMD was associated with training load (r = 0.560, P = 0.003) and ankle (r = 0.710, P = 0.004) and knee (r = 0.546, P = 0.043) joint stiffness. Elite Kenyan runners exhibit greater PFBMD than healthy controls, which is associated with higher training load and higher joint stiffness. Our results reaffirm the benefits of impact loading on BMD at a weight-bearing site, while a high prevalence of low LSBMD in the elite Kenyan runners is hypothesised to be the result of a mismatch between energy intake and high training load. Future research investigating energy availability in Kenyan runners and the possible association with musculoskeletal injury should be investigated.

Conceptualizing minimalist footwear: an objective definition.

Running has been plagued with an alarmingly high incidence of injury, which has resulted in the exploration of interventions aimed at reducing the risk of running-related injury. One such intervention is the introduction of footwear that mimics barefoot running. These have been termed minimalist shoes. Minimalist footwear aims to reduce the risk of injury by promoting adaptations in running biomechanics that have been linked to a reduction in both impact and joint forces. However, some studies have found that minimalist footwear may be beneficial to the runner as they promote favourable biomechanical adaptations, whilst other studies have found the opposite to be true. Reasons for these conflicting results could be attributed to the lack of a definition for minimalist footwear. The aim of this review article is to provide a structural definition for minimalist footwear based on studies that have examined the influence of footwear on biomechanical variables during running. Based on current literature, we define minimalist footwear as a shoe with a highly flexible sole and upper that weighs 200g or less, has a heel stack height of 20mm or less and a heel-toe differential of 7mm or less.

Habitual Minimalist Shod Running Biomechanics and the Acute Response to Running Barefoot.

The aim of the study was to determine whether habitual minimalist shoe runners present with purported favorable running biomechanithat reduce running injury risk such as initial loading rate. Eighteen minimalist and 16 traditionally cushioned shod runners were assessed when running both in their preferred training shoe and barefoot. Ankle and knee joint kinetics and kinematics, initial rate of loading, and footstrike angle were measured. Sagittal ankle and knee joint stiffness were also calculated. Results of a two-factor ANOVA presented no group difference in initial rate of loading when participants were running either shod or barefoot; however, initial loading rate increased for both groups when running barefoot (p=0.008). Differences in footstrike angle were observed between groups when running shod, but not when barefoot (minimalist:8.71±8.99 vs. traditional: 17.32±11.48 degrees, p=0.002). Lower ankle joint stiffness was found in both groups when running barefoot (p=0.025). These findings illustrate that risk factors for injury potentially differ between the two groups. Shoe construction differences do change mechanical demands, however, once habituated to the demands of a given shoe condition, certain acute favorable or unfavorable responses may be moderated. The purported benefits of minimalist running shoes in mimicking habitual barefoot running is questioned, and risk of injury may not be attenuated.

Biomechanical analysis of gait waveform data: exploring differences between shod and barefoot running in habitually shod runners.

The aim of this study was to utilise one-dimensional statistical parametric mapping to compare differences between biomechanical and electromyographical waveforms in runners when running in barefoot or shod conditions. Fifty habitually shod runners were assessed during overground running at their current 10-km race running speed. Electromyography, kinematics and ground reaction forces were collected during these running trials. Joint kinetics were calculated using inverse dynamics. One-dimensional statistical parametric mapping one sample t-test was conducted to assess differences over an entire gait cycle on the variables of interest when barefoot or shod (p<0.05). Only sagittal plane differences were found between barefoot and shod conditions at the knee during late stance (18-23% of the gait cycle) and swing phase (74-90%); at the ankle early stance (0-6%), mid-stance (28-38%) and swing phase (81-100%). Differences in sagittal plane moments were also found at the ankle during early stance (2, 4-5%) and knee during early stance (5-11%). Condition differences were also found in vertical ground reaction force during early stance between (3-10%). An acute bout of barefoot running in habitual shod runners invokes temporal differences throughout the gait cycle. Specifically, a co-ordinative responses between the knee and ankle joint in the sagittal plane with a delay in the impact transient peak; onset of the knee extension and ankle plantarflexion moment in the shod compared to barefoot condition was found. This appears to affect the delay in knee extension and ankle plantarflexion during late stance. This study provides a glimpse into the co-ordination of the lower limb when running in differing footwear.

Acute fatigue negatively affects risk factors for injury in trained but not well-trained habitually shod runners when running barefoot.

INTRODUCTION: Many factors may contribute to running-related injury. These include fatigue and footwear, the combination of which has rarely been studied, in particular with reference to barefoot running, recently advocated as a method to reduce injury risk. METHODS: Twenty-two runners (12 well-trained and 10 trained) participated in a 10 km fatiguing trial. Knee and ankle joint kinematics and kinetics and electromyography were assessed during overground running in the barefoot and shod condition. This was performed pre- and post-fatigue using a motion capture system and force platforms. RESULTS: Initial loading rate increased in the trained runners when barefoot but not shod. Shod knee stiffness increased in both groups after fatigue, whereas barefoot knee stiffness decreased only in the trained group. A reduction in barefoot bicep femoris pre-activation was found in both groups. During stance, a reduction in vastus lateralis and biceps femoris and an increase in tibialis anterior activity were found over time in both groups and conditions. Trained runners decreased gluteus medius and increased lateral gastrocnemius median frequency for both conditions after fatigue. CONCLUSION: When fatigued, gait adjustments in habitually shod runners may increase injury risk when running barefoot. Training status may be a risk factor for injury, as less-trained runners experience muscular fatigue changes that may compromise ground reaction force attenuation. Caution is recommended when transitioning to pure barefoot running.

Submaximal Markers of Fatigue and Overreaching; Implications for Monitoring Athletes.

The regular monitoring of athletes is important to fine-tune training and detect early symptoms of overreaching. Therefore the aim of this study was to determine if a noninvasive submaximal running test could reflect a state of overreaching. 14 trained runners completed a noninvasive Lamberts Submaximal Running Test, one week before and 2 days after finishing an ultramarathon, and delayed onset of muscle soreness and the daily analysis of life demands for athletes questionnaire were also captured. After the ultramarathon, submaximal heart rate was lower at 70% (-3 beats) and 85% of peak treadmill running speed (P<0.01). Ratings of perceived exertion were higher at 60% (2 units) and 85% (one unit) of peak treadmill running speed, while 60-second heart rate recovery was significantly faster (7 beats, P<0.001). Delayed Onset of Muscle Soreness scores and the number of symptoms of stress (Daily Analysis of Life Demands for Athletes) were also higher after the ultramarathon (P<0.01). The current study shows that the Lamberts Submaximal Running Test is able to reflect early symptoms of overreaching. Responses to acute fatigue and overreaching were characterized by counterintuitive responses, such as lower submaximal heart rates and faster heart rate recovery, while ratings of perceived exertion were higher.