Jason Bonacci

Running in a minimalist and lightweight shoe is not the same as running barefoot: a biomechanical study

Aim The purpose of this study was to determine the changes in running mechanics that occur when highly trained runners run barefoot and in a minimalist shoe, and specifically if running in a minimalist shoe replicates barefoot running. Methods Ground reaction force data and kinematics were collected from 22 highly trained runners during overground running while barefoot and in three shod conditions (minimalist shoe, racing flat and the athletes regular shoe). Three-dimensional net joint moments and subsequent net powers and work were computed using Newton-Euler inverse dynamics. Joint kinematic and kinetic variables were statistically compared between barefoot and shod conditions using a multivariate analysis of variance for repeated measures and standardised mean differences calculated. Results There were significant differences between barefoot and shod conditions for kinematic and kinetic variables at the knee and ankle, with no differences between shod conditions. Barefoot running demonstrated less knee flexion during midstance, an 11% decrease in the peak internal knee extension and abduction moments and a 24% decrease in negative work done at the knee compared with shod conditions. The ankle demonstrated less dorsiflexion at initial contact, a 14% increase in peak power generation and a 19% increase in the positive work done during barefoot running compared with shod conditions. Conclusions Barefoot running was different to all shod conditions. Barefoot running changes the amount of work done at the knee and ankle joints and this may have therapeutic and performance implications for runners.

Take your shoes off to reduce patellofemoral joint stress during running

Aim Elevated patellofemoral joint stress is thought to contribute to the development and progression of patellofemoral pain syndrome. The purpose of this study was to determine if running barefoot decreases patellofemoral joint stress in comparison to shod running. Methods Lower extremity kinematics and ground reaction force data were collected from 22 trained runners during overground running while barefoot and in a neutral running shoe. The kinematic and kinetic data were used as input variables into a previously described mathematical model to determine patellofemoral joint stress. Knee flexion angle, net knee extension moment and the model outputs of contact area, patellofemoral joint reaction force and patellofemoral joint stress were plotted over the stance phase of the gait cycle and peak values compared using paired t tests and standardised mean differences calculated. Results Running barefoot decreased peak patellofemoral joint stress by 12% (p=0.000) in comparison to shod running. The reduction in patellofemoral joint stress was a result of reduced patellofemoral joint reaction forces (12%, p=0.000) while running barefoot. Conclusions Elevated patellofemoral joint stress during shod running might contribute to patellofemoral pain. Running barefoot decreases patellofemoral joint stress.

Neuromuscular adaptations to training, injury and passive interventions: implications for running economy

Performance in endurance sports such as running, cycling and triathlon has long been investigated from a physiological perspective. A strong relationship between running economy and distance running performance is well established in the literature. From this established base, improvements in running economy have traditionally been achieved through endurance training. More recently, research has demonstrated short-term resistance and plyometric training has resulted in enhanced running economy. This improvement in running economy has been hypothesized to be a result of enhanced neuromuscular characteristics such as improved muscle power development and more efficient use of stored elastic energy during running. Changes in indirect measures of neuromuscular control (i.e. stance phase contact times, maximal forward jumps) have been used to support this hypothesis. These results suggest that neuromuscular adaptations in response to training (i.e. neuromuscular learning effects) are an important contributor to enhancements in running economy. However, there is no direct evidence to suggest that these adaptations translate into more efficient muscle recruitment patterns during running. Optimization of training and run performance may be facilitated through direct investigation of muscle recruitment patterns before and after training interventions.There is emerging evidence that demonstrates neuromuscular adaptations during running and cycling vary with training status. Highly trained runners and cyclists display more refined patterns of muscle recruitment than their novice counterparts. In contrast, interference with motor learning and neuromuscular adaptation may occur as a result of ongoing multidiscipline training (e.g. triathlon). In the sport of triathlon, impairments in running economy are frequently observed after cycling. This impairment is related mainly to physiological stress, but an alteration in lower limb muscle coordination during running after cycling has also been observed. Muscle activity during running after cycling has yet to be fully investigated, and to date, the effect of alterations in muscle coordination on running economy is largely unknown. Stretching, which is another mode of training, may induce acute neuromuscular effects but does not appear to alter running economy.There are also factors other than training structure that may influence running economy and neuromuscular adaptations. For example, passive interventions such as shoes and in-shoe orthoses, as well as the presence of musculoskeletal injury, may be considered important modulators of neuromuscular control and run performance. Alterations in muscle activity and running economy have been reported with different shoes and in-shoe orthoses; however, these changes appear to be subject-specific and nonsystematic. Musculoskeletal injury has been associated with modifications in lower limb neuromuscular control, which may persist well after an athlete has returned to activity. The influence of changes in neuromuscular control as a result of injury on running economy has yet to be examined thoroughly, and should be considered in future experimental design and training analysis.

Change in running kinematics after cycling are related to alterations in running economy in triathletes

Emerging evidence suggests that cycling may influence neuromuscular control during subsequent running but the relationship between altered neuromuscular control and run performance in triathletes is not well understood. The aim of this study was to determine if a 45 min high-intensity cycle influences lower limb movement and muscle recruitment during running and whether changes in limb movement or muscle recruitment are associated with changes in running economy (RE) after cycling. RE, muscle activity (surface electromyography) and limb movement (sagittal plane kinematics) were compared between a control run (no preceding cycle) and a run performed after a 45 min high-intensity cycle in 15 moderately trained triathletes. Muscle recruitment and kinematics during running after cycling were altered in 7 of 15 (46%) triathletes. Changes in kinematics at the knee and ankle were significantly associated with the change in VO(2) after cycling (p<0.05). The change in ankle angle at foot contact alone explained 67.1% of the variance in VO(2). These findings suggest that cycling does influence limb movement and muscle recruitment in some triathletes and that changes in kinematics, especially at the ankle, are closely related to alterations in running economy after cycling.

What is Normal? Female Lower Limb Kinematic Profiles During Athletic Tasks Used to Examine Anterior Cruciate Ligament Injury Risk: A Systematic Review

BackgroundIt has been proposed that the performance of athletic tasks where normal motion is exceeded has the potential to damage the anterior cruciate ligament (ACL). Determining the expected or ‘normal’ kinematic profile of athletic tasks commonly used to assess ACL injury risk can provide an evidence base for the identification of abnormal or anomalous task performances in a laboratory setting.ObjectiveThe objective was to conduct a systematic review of studies examining lower limb kinematics of females during drop landing, drop vertical jump, and side-step cutting tasks, to determine ‘normal’ ranges for hip and knee joint kinematic variables.Data SourcesAn electronic database search was conducted on the SPORTDiscusTM, MEDLINE, AMED and CINAHL (January 1980–August 2013) databases using a combination of relevant keywords.Study SelectionStudies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined three-dimensional hip and knee kinematics of female subjects during the athletic tasks of interest were included for review. Articles were excluded if subjects had a history of lower back or lower limb joint injury or isolated data from the female cohort could not be extracted.Study Appraisal and Synthesis MethodsTwo reviewers independently assessed the quality of included studies. Data on subject characteristics, the athletic task performed, and kinematic data were extracted from included studies. Studies were categorised according to the athletic task being examined and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate the weighted means and standard deviations for hip and knee kinematics (initial contact and peak values). ‘Normal’ motion was classified as the weighted mean plus/minus one standard deviation.ResultsOf 2,920 citations, a total of 159 articles were identified as potentially relevant, with 29 meeting all inclusion/exclusion criteria. Due to the limited number of studies available examining double-leg drop landings and single-leg drop vertical jumps, insufficient data was available to include these tasks in the review. Therefore, a total of 25 articles were included. From the included studies, ‘normal’ ranges were calculated for the kinematic variables of interest across the athletic tasks examined.LimitationsJoint forces and other additional elements play a role in ACL injuries, therefore, focusing solely on lower limb kinematics in classifying injury risk may not encapsulate all relevant factors. Insufficient data resulted in no normal ranges being calculated for double-leg drop land and single-leg drop vertical jump tasks. No included study examined hip internal/external rotation during single-leg drop landings, therefore ranges for this kinematic variable could not be determined. Variation in data between studies resulted in wide normal ranges being observed across certain kinematic variables.ConclusionsThe ranges calculated in this review provide evidence-based values that can be used to identify abnormal or anomalous athletic task performances on a multi-planar scale. This may be useful in identifying neuromuscular factors or specific muscular recruitment strategies that contribute to ACL injury risk.

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 low-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.

A Systematic Evaluation of Field-Based Screening Methods for the Assessment of Anterior Cruciate Ligament (ACL) Injury Risk

BackgroundLaboratory-based measures provide an accurate method to identify risk factors for anterior cruciate ligament (ACL) injury; however, these methods are generally prohibitive to the wider community. Screening methods that can be completed in a field or clinical setting may be more applicable for wider community use. Examination of field-based screening methods for ACL injury risk can aid in identifying the most applicable method(s) for use in these settings.ObjectiveThe objective of this systematic review was to evaluate and compare field-based screening methods for ACL injury risk to determine their efficacy of use in wider community settings.Data SourcesAn electronic database search was conducted on the SPORTDiscus™, MEDLINE, AMED and CINAHL databases (January 1990–July 2015) using a combination of relevant keywords. A secondary search of the same databases, using relevant keywords from identified screening methods, was also undertaken.Study SelectionStudies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined screening methods for ACL injury risk that could be undertaken outside of a laboratory setting were included for review.Study Appraisal and Synthesis MethodsTwo reviewers independently assessed the quality of included studies. Included studies were categorized according to the screening method they examined. A description of each screening method, and data pertaining to the ability to prospectively identify ACL injuries, validity and reliability, recommendations for identifying ‘at-risk’ athletes, equipment and training required to complete screening, time taken to screen athletes, and applicability of the screening method across sports and athletes were extracted from relevant studies.ResultsOf 1077 citations from the initial search, a total of 25 articles were identified as potentially relevant, with 12 meeting all inclusion/exclusion criteria. From the secondary search, eight further studies met all criteria, resulting in 20 studies being included for review. Five ACL-screening methods—the Landing Error Scoring System (LESS), Clinic-Based Algorithm, Observational Screening of Dynamic Knee Valgus (OSDKV), 2D-Cam Method, and Tuck Jump Assessment—were identified. There was limited evidence supporting the use of field-based screening methods in predicting ACL injuries across a range of populations. Differences relating to the equipment and time required to complete screening methods were identified.LimitationsOnly screening methods for ACL injury risk were included for review. Field-based screening methods developed for lower-limb injury risk in general may also incorporate, and be useful in, screening for ACL injury risk.ConclusionsLimited studies were available relating to the OSDKV and 2D-Cam Method. The LESS showed predictive validity in identifying ACL injuries, however only in a youth athlete population. The LESS also appears practical for community-wide use due to the minimal equipment and set-up/analysis time required. The Clinic-Based Algorithm may have predictive value for ACL injury risk as it identifies athletes who exhibit high frontal plane knee loads during a landing task, but requires extensive additional equipment and time, which may limit its application to wider community settings.

Mechanical ageing performance of minimalist and traditional footwear foams

The aim of this study was to obtain a fundamental understanding of how running shoe midsole foam thickness contributes to footwear degradation using the heel and forefoot regions of traditional (TS) and minimalist (MS) running shoes. We hypothesized that ethylene vinyl acetate (EVA) foam midsole material properties and footwear degradation performance under a biofidelic mechanical ageing protocol would differ as a function of shoe type and thickness. Attenuated total reflectance Fourier transform infrared spectra indicated that the foam chemical compositions were similar and confirmed that all midsoles were composed of EVA copolymer. Differences in density and cell size were detected between shoes and thicknesses. MS foam was uniformly high density (ρMS = 240 kg/m3), while TS foam consisted of two co-molded layers with forefoot density (ρTS-FF = 250 kg/m3) greater than heel (ρTS-H = 160 kg/m3). Relative density and cell size values were generally proportional and inversely proportional to density, respectively. Degradation from mechanical ageing was greatest in the first 2 km of ageing, with the full ageing (21 km) resulting in an average 54% loss of energy absorption. Regardless of shoe type or foam microstructure, thicker and softer heel foams absorbed 83% more energy but degraded at a 49% faster rate. The fact that the heel degraded more rapidly than forefoot caused the drop to decrease at an equivalent rate for both shoe types. Overall, thickness was a greater predictor of average performance than microstructure variables for the present footwear conditions. However, the apparent drawback of thicker foam was exemplified by heel samples, which underwent a 1.4 mm greater loss of thickness and lost 550 mJ more energy absorption than forefoot samples.

Gluteus medius activation during running is a risk factor for season hamstring injuries in elite footballers

OBJECTIVES To investigate if size and activation of the gluteal muscles is a risk factor for hamstring injuries in elite AFL players. DESIGN Prospective cohort study. METHODS Twenty-six elite male footballers from a professional Australian Football League (AFL) club participated in the study. At the beginning of the season bilateral gluteus medius (GMED) and gluteus maximus (GMAX) muscle volume was measured from magnetic resonance images and electromyographic recordings of the same muscles were obtained during running. History of hamstring injury in the pre-season and incidence of hamstring injury during the season were determined from club medical data. RESULTS Nine players (35%) incurred a hamstring injury during the season. History of hamstring injury was comparable between those players who incurred a season hamstring injury (2/9 players; 22%) and those who did not (3/17 players; 18%). Higher GMED muscle activity during running was a risk factor for hamstring injury (p=0.03, effect sizes 1.1-1.5). There were no statistically significant differences observed for GMED volume, GMAX volume and GMAX activation (P>0.05). CONCLUSIONS This study identified higher activation of the GMED muscle during running in players who sustained a season hamstring injury. Whilst further research is required to understand the mechanism of altered muscle control, the results of this study contribute to the developing body of evidence that the lumbo-pelvic muscles may be important to consider in hamstring injury prevention and management.

Gait retraining versus foot orthoses for patellofemoral pain: a pilot randomised clinical trial

OBJECTIVES To determine the feasibility of a clinical trial that compares a 6-week, physiotherapist-guided gait retraining program with a foot orthoses intervention in runners with patellofemoral pain. DESIGN Pilot randomised controlled trial. METHODS Runners aged 18-40 years with clinically diagnosed patellofemoral pain were randomly allocated to either a 6-week gait retraining intervention of increasing cadence and use of a minimalist shoe or prefabricated foot orthoses. Outcomes at baseline and 12-weeks included recruitment, retention, adherence, adverse events, global improvement, anterior knee pain scale, worst and average pain on a 100mm visual analogue scale. RESULTS Of the 16 randomised participants, two withdrew prior to commencing treatment due to non-trial related matters (n=1 from each group) and 14 completed the pilot trial. Minor calf muscle soreness was reported by 3 participants in the gait retraining group while no adverse events were reported in the foot orthoses group. There were no deviations from the treatment protocols. There was a large between-group difference favouring gait retraining at 12-weeks in the anterior knee pain scale and the worst pain in the past week, which was reflected in the number needed-to-treat of 2. CONCLUSIONS This study supports the feasibility of a trial comparing gait retraining with foot orthoses and provides point estimates of effect that informs the design and planning of a larger clinical trial. It appears that a 6-week gait retraining program has a clinically meaningful effect on runners with patellofemoral pain when compared to an evidence-based treatment of foot orthoses.