Nicholas Tam

Barefoot running: an evaluation of current hypothesis, future research and clinical applications

Barefoot running has become a popular research topic, driven by the increasing prescription of barefoot running as a means of reducing injury risk. Proponents of barefoot running cite evolutionary theories that long-distance running ability was crucial for human survival, and proof of the benefits of natural running. Subsequently, runners have been advised to run barefoot as a treatment mode for injuries, strength and conditioning. The body of literature examining the mechanical, structural, clinical and performance implications of barefoot running is still in its infancy. Recent research has found significant differences associated with barefoot running relative to shod running, and these differences have been associated with factors that are thought to contribute to injury and performance. Crucially, long-term prospective studies have yet to be conducted and the link between barefoot running and injury or performance remains tenuous and speculative. The injury prevention potential of barefoot running is further complicated by the complexity of injury aetiology, with no single factor having been identified as causative for the most common running injuries. The aim of the present review was to critically evaluate the theory and evidence for barefoot running, drawing on both collected evidence as well as literature that have been used to argue in favour of barefoot running. We describe the factors driving the prescription of barefoot running, examine which of these factors may have merit, what the collected evidence suggests about the suitability of barefoot running for its purported uses and describe the necessary future research to confirm or refute the barefoot running hypotheses.

Changes in total body water content during running races of 21.1 km and 56 km in athletes drinking ad libitum.

Objective:To measure changes in body mass (BM), total body water (TBW), fluid intake, and blood biochemistry in athletes during 21.1-km and 56-km foot races. Design:Observational study. Setting:2009 Two Oceans Marathon, South Africa. Participants:Twenty-one (21.1 km) and 12 (56 km) participants were advised to drink according to thirst or their own race drink plan (ad libitum). Main Outcome Measures:Body mass, TBW, plasma osmolality, plasma sodium (p[Na+]), and plasma total protein ([TP]) concentrations were measured before and after race. Fluid intake was recorded from recall after race. Results:Significant BM loss occurred in both races (21.1 km; −1.4 ± 0.6 kg; P < 0.000 and 56 km; −2.5 ± 1.1 kg; P < 0.000). Total body water was reduced in the 56-km race (−1.4 ± 1.1 kg; P < 0.001). A negative linear relationship was found between percentage change (%Δ) in TBW and %Δ in BM in the 56-km runners (r = 0.6; P < 0.01). Plasma osmolality and [TP] increased significantly in the 56-km runners (6.8 ± 8.2 mOsm/kg H2O; P < 0.05 and 5.4 ± 4.4 g/L; P < 0.01, respectively), but all other biochemical measures were within the normal range. Conclusions:Although TBW decreased in the 56-km race and was maintained in the 21.1-km race, the change in TBW over both races was less than the BM, suggesting that not all BM lost during endurance exercise is a result purely of an equivalent reduction in TBW. These findings support the interpretation that the body primarily defends p[Na+] and not BM during exercise and that a reduction in BM can occur without an equivalent reduction in TBW during prolonged exercise. Furthermore, these data support that drinking without controlling for BM loss may allow athletes to complete these events.

Gait status 17–26 years after selective dorsal rhizotomy

The purpose of this study was to use three-dimensional gait analysis to describe the gait status of adults with spastic diplegia who underwent selective dorsal rhizotomy (SDR) in childhood. Outcome measures were the gait deviation index (GDI), non-dimensional temporal-distance parameters, and kinematics of the lower limbs. A total of 31 adults with spastic diplegia who had previously undergone SDR were eligible and participated in current study (SDR group). These participants had a median age of 26.8 years (range 21-44 years) with a mean time between surgery and assessment of 21.2±2.9 years (range 17-26 years). For comparison purposes, 43 typically developed adults also participated (CONTROL group), with a median age of 28.3 years (range 21-45 years). More than 17 years after SDR 58% of the SDR group showed improved GMFCS levels, while none of them deteriorated. The participants in the SDR group walked with a mild crouch gait, although there was a loading response, adequate swing-phase knee flexion, adequate swing-phase plantarflexion, reasonable speed and cadence. The gait status of the SDR group more than 17 years after SDR was similar to what has been reported in short-term follow-up studies, as well as our earlier 20 year follow-up study that did not include 3D gait analysis. Appropriate orthopaedic intervention was required in 61% of the study cohort. Whether the types and numbers of orthopaedic interventions are positively affected by SDR remains an open question. Further studies examining this question are warranted. In addition, long-term follow-up studies focused on other interventions would also be of clinical relevance.

Differences in ground contact time explain the less efficient running economy in north african runners.

The purpose of this study was to investigate the relationship between biomechanical variables and running economy in North African and European runners. Eight North African and 13 European male runners of the same athletic level ran 4-minute stages on a treadmill at varying set velocities. During the test, biomechanical variables such as ground contact time, swing time, stride length, stride frequency, stride angle and the different sub-phases of ground contact were recorded using an optical measurement system. Additionally, oxygen uptake was measured to calculate running economy. The European runners were more economical than the North African runners at 19.5 km · h−1, presented lower ground contact time at 18 km · h−1 and 19.5 km · h−1 and experienced later propulsion sub-phase at 10.5 km · h−1,12 km · h−1, 15 km · h−1, 16.5 km · h−1 and 19.5 km · h−1 than the European runners (P < 0.05). Running economy at 19.5 km · h−1 was negatively correlated with swing time (r = -0.53) and stride angle (r = -0.52), whereas it was positively correlated with ground contact time (r = 0.53). Within the constraints of extrapolating these findings, the less efficient running economy in North African runners may imply that their outstanding performance at international athletic events appears not to be linked to running efficiency. Further, the differences in metabolic demand seem to be associated with differing biomechanical characteristics during ground contact, including longer contact times.

Stride Angle as a Novel Indicator of Running Economy in Well-Trained Runners

Abstract Santos-Concejero, J, Tam, N, Granados, C, Irazusta, J, Bidaurrazaga-Letona, I, Zabala-Lili, J, and Gil, SM. Stride angle as a novel indicator of running economy in well-trained runners. J Strength Cond Res 28(7): 1889–1895, 2014—The main purpose of this study was to investigate the relationship between a novel biomechanical variable, the stride angle, and running economy (RE) in a homogeneous group of long-distance athletes. Twenty-five well-trained male runners completed 4-minute running stages on a treadmill at different set velocities. During the test, biomechanical variables such as stride angle, swing time, ground contact time, stride length, stride frequency, and the different sub-phases of ground contact were recorded using an optical measurement system. V[Combining Dot Above]O2 values at velocities below the lactate threshold were measured to calculate RE. Stride angle was negatively correlated with RE at every speed (p < 0.001, large effect sizes). Running economy was also negatively correlated with swing phase and positively correlated with ground contact time and running performance according to the best 10-km race time (p ⩽ 0.05, moderate and large effect sizes). Last, stride angle was correlated with ground contact time at every speed (p < 0.001, large effect sizes). In conclusion, it seems that optimal execution of stride angle allows runners to minimize contact time during ground contact, whereby facilitating a better RE. Coaches and/or athletes may find stride angle a useful and easily obtainable measure to track and make alterations to running technique, because changes in stride angle may influence the energy cost of running and lead to improved performance.

Interaction effects of stride angle and strike pattern on running economy.

This study aimed to investigate the relationship between stride angle and running economy (RE) in athletes with different foot strike patterns. 30 male runners completed 4 min running stages on a treadmill at different velocities. During the test, biomechanical variables such as stride angle, swing time, contact time, stride length and frequency were recorded using an optical measurement system. Their foot strike pattern was determined, and VO2 at velocities below the lactate threshold were measured to calculate RE. Midfoot/forefoot strikers had better RE than rearfoot strikers (201.5±5.6 ml · kg(-1) · km(-1) vs. 213.5±4.2 ml · kg(-1) · km(-1)respectively; p=0.019). Additionally, midfoot/fore-foot strikers presented higher stride angles than rearfoot strikers (p=0.043). Linear modelling analysis showed that stride angle is closely related to RE (r=0.62, p<0.001) and that the effect of stride angle on RE was different in the 2 groups. From an arbitrary value of 4°, a rearfoot strike pattern is likely to be more economical, whereas at any lower degree, the midfoot/forefoot strike pattern appears to be more desirable. A biomechanical running technique characterised by high stride angles and a midfoot/forefoot strike pattern is advantageous for a better RE. Athletes may find stride angle useful for improving RE.

Individual Responses to a Barefoot Running Program Insight Into Risk of Injury

Background: Barefoot running is of popular interest because of its alleged benefits for runners, including reduced injury risk and increased economy of running. There is a dearth in understanding whether all runners can gain the proposed benefits of barefoot running and how barefoot running may affect long-term injury risk. Purpose/Hypothesis: The purpose of this study was to determine whether runners can achieve the proposed favorable kinematic changes and reduction in loading rate after a progressive training program that included barefoot running. It was hypothesized that not all individuals would experience a decrease in initial loading rate facilitated by increased ankle plantar flexion after a progressive barefoot running program; it was further hypothesized that relationships exist between changes in initial loading rate and sagittal ankle angle. Study Design: Descriptive laboratory study. Methods: A total of 26 habitually shod runners completed an 8-week, progressively introduced barefoot running program. Pre- and postintervention barefoot and shod kinematics, electromyography, and ground-reaction force data of the lower limb were collected. Ankle and knee kinematics and kinetics, initial loading rates, spatiotemporal variables, muscle activity during preactivation, and ground contact were assessed in both conditions before and after the intervention. Individual responses were analyzed by separating runners into nonresponders, negative responders, and positive responders based on no change, increase, and decrease in barefoot initial loading rate, respectively. Results: No biomechanical changes were found in the group after the intervention. However, condition differences did persist during both preactivation and ground contact. The positive-responder group had greater plantar flexion, increased biceps femoris and gluteus medius preactivation, and decreased rectus femoris muscle activity between testing periods. The negative responders landed in greater barefoot dorsiflexion after the intervention, and the nonresponders did not change. An overall change in ankle flexion angle was associated with a change in initial loading rate (r2 = 0.345, P = .002) in the barefoot but not shod condition. Conclusion: Eight weeks of progressive barefoot running did not change overall group biomechanics, but subgroups of responders (25% of the entire group) were identified who had specific changes that reduced the initial loading rate. It appears that changes in initial loading rate are explained by changes in ankle flexion angle at initial ground contact. Clinical Relevance: Uninstructed barefoot running training does not reduce initial loading rate in all runners transitioning from shod to barefoot conditions. Some factors have been identified that may assist sports medicine professionals in the evaluation and management of runners at risk of injury. Conscious instruction to runners may be required for them to acquire habitual barefoot running characteristics and to reduce risk of injury.

Are gait characteristics and ground reaction forces related to energy cost of running in elite Kenyan runners

ABSTRACT The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h−1 and 20 km ·h−1). VO2 and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg−1· km−1 at 12 km· h−1 and 184.8 ± 9.9 ml· kg−1· km−1 at 20 km· h−1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg−1·km−1 and 0.93 ± 0.07 kcal· kg−1· km−1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h−1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners.

Loading rate increases during barefoot running in habitually shod runners: Individual responses to an unfamiliar condition

The purpose of this study was to examine the effect of barefoot running on initial loading rate (LR), lower extremity joint kinematics and kinetics, and neuromuscular control in habitually shod runners with an emphasis on the individual response to this unfamiliar condition. Kinematics and ground reaction force data were collected from 51 habitually shod runners during overground running in a barefoot and shod condition. Joint kinetics and stiffness were calculated with inverse dynamics. Inter-individual initial LR variability was explored by separating individuals by a barefoot/shod ratio to determine acute responders/non-responders. Mean initial LR was 54.1% greater in the barefoot when compared to the shod condition. Differences between acute responders/non-responders were found at peak and initial contact sagittal ankle angle and at initial ground contact. Correlations were found between barefoot sagittal ankle angle at initial ground contact and barefoot initial LR. A large variability in biomechanical responses to an acute exposure to barefoot running was found. A large intra-individual variability was found in initial LR but not ankle plantar-dorsiflexion between footwear conditions. A majority of habitually shod runners do not exhibit previously reported benefits in terms of reduced initial LRs when barefoot. Lastly, runners who increased LR when barefoot reduced LRs when wearing shoes to levels similar seen in habitually barefoot runners who do adopt a forefoot-landing pattern, despite increased dorsiflexion.

Muscle co-activation and its influence on running performance and risk of injury in elite Kenyan runners

ABSTRACT The relationship between muscle co-activation and energy cost of transport and risk of injury (initial loading rate and joint stiffness) has not been jointly studied. Fourteen elite Kenyan male runners were tested at two speeds (12 and 20 km · h−1), where oxygen consumption, kinematic, kinetic and electromyography were recorded. Electromyography of seven lower limb muscles was recorded. Pre-activation and ground contact of agonist:antagonist co-activation was determined. All muscles displayed higher activity during pre-activation except rectus femoris (RF). Conversely, no differences were found during ground contact except for higher biceps femoris (BF) at 20 km · h−1. Knee stiffness was correlated to RF–BF co-activation during both pre-activation and ground contact at both running speeds. However, energy cost of transport was only positively correlated to the above-mentioned muscle pairs at 20 km · h−1 (r = 0620, P = 0.032; r = 0.682, P = 0.015, respectively). These findings emphasise the influence of neuromuscular control and performance and its support to musculoskeletal system to optimise function and modulate risk of injury. Further, neuromuscular activity during terminal swing is also important and necessary to execute and maintain performance.