The right foot forward, or the right shoe? A comparative review of barefoot and shod running.

Research Question Hypothesis: There are biomechanical differences between shod and barefoot running. Null Hypothesis: There are no biomechanical differences between shod and barefoot running. To investigate this… We performed a literature review

Studies suggest that barefoot runners: Background Proposed benefits of modern running shoes include stability, cushioning, performance and injury reduction Running shoes have a short history. Prior to their introduction humans ran barefoot Studies suggest that barefoot runners: Strike the ground with a more plantarflexed foot Increase stride frequency and decrease contact time Decrease stride length Experience reduced impact forces Plantar flexed Stride length Impact forces

Methods Literature pertaining to barefoot running was found on the NIH PubMed database Search Terms: “bare foot”, “barefoot”, “barefeet” and “bare feet” in title/abstract. MeSH: “running” Inclusion criteria: 1) Published after 1985 2) English 3) At least one subject group of barefoot runners Exclusion criteria: 1) Published before 1985 2)Trials included only barefoot walkers or shod runners 63 papers found. 39 met inclusion/exclusion criteria In order to investigate the validity the four characteristics of barefoot running and the proposed benefits of running shoes: introduce bulletpoints

Results: Impact and loading patterns 75-91% habitually barefoot runners FFS Approximately 85% of shod runners RFS Increased cadence, decreased contact time, shorter stride length Barefoot: Peak pressures under heel and 2nd met. Highest impulse under 2nd met, lowest impulse under heel Shod: Peak pressures under heel, midfoot and hallux. Highest impulse under heel Ground Reaction Forces Barefoot rearfoot strike (RFS): highest impact transient Shod RFS: distinct impact transient Barefoot forefoot strike (FFS): minimal impact transient Peak GRF similar Arun: explain the image= barefoot heel-strike running gait, 8 areas identified. Bulletpoint 3=De Cock et al attribute this shortening to the activation of the intrinsic muscles of the foot, normally inactive in shoes.

Results: Joint Movement and Coupling Barefoot: Significantly more plantarflexed foot at contact regardless of footstrike pattern. Increasing plantarflexion with barefoot accommodation Suggestive of reduced rearfoot and forefoot frontal plane motion Reduced eversion velocity Shod: Dorsiflexed foot at contact Suggestive of greater rearfoot and forefoot frontal motion Increased eversion velocity Increased hip internal rotation and knee varus torques Rearfoot-tibial coupling unchanged by condition. Sagittal plane knee motion is inconsistent

Results: Muscle Activation Barefoot Gastroc-soleus: stronger, earlier activation (regardless of footstrike pattern) Tibialis Anterior: stronger, and earlier activation (post-heel-strike) Spinal Muscles: increase in loading rate, increase in response time to heel-strike, and decrease in time interval between peak lumbar acceleration and peak lumbar muscle response. Medial Longitudinal Arch: significantly shortens with increased weight bearing activity. Shod Tibialis Anterior: stronger (pre-heel-strike) Peroneus Longus: increased activity, based on increased heel height, which everts the shod foot when put under inversion stress Results: Muscle Activation

Results: Sensitivity and feedback Unshod runners experience a greater amount of heel fat pad deformity and compression. (9±5mm versus 5.5±.2mm) The heel region of the foot was shown to have the highest pain threshold, the hallux intermediate, while 1st MPJ had the lowest Feedback training was tested using peak positive tibial acceleration. 70% reduction of peak positive tibial acceleration immediately after one training session. 80% reduction ten minutes after 1st feedback training session.

Discussion Barefoot runners have a characteristically different gait pattern than shod runners Forefoot strike, faster cadence, decreased contact time, shorter strides Impact reduction and efficiency improvement Dissipates impact forces in the sagittal plane Greater elastic return in Achilles tendon Reduced weight Heel striking appears to translate impact forces into excessive rearfoot pronation, tibial rotation, and possibly knee flexion

Discussion Biomechanical model of barefoot gait Forefoot strike at lateral forefoot. Preactivated gastroc-soleus Mild forefoot pronation followed by controlled heel contact and mild rearfoot pronation Metatarsal splay Neutral midstance. Greater potential energy storage in Achilles tendon Reduced overall contact time Mild rearfoot and forefoot inversion at toeoff. Reduced stride length. Increased cadence

Discussion Running efficiency was found to be influenced by, not just shoe mass, but shoe shape (proven using a thin, flexible, foot covering of the same weight as a shoe). Heel height may reduce efficiency. Are minimal shoes a solution? Does barefoot running or a forefoot strike reduce injury risk? What are the tradeoffs?

Future Research Opportunities No injury data available Longitudinal study of injuries in barefoot and shod runners: fat pad atrophy, ground reaction forces Control for mileage and intensity Testing foot intrinsic muscle strength Literature has yet to look at minimalist shoe design (minimal cushion and low heel lift) Are the major manufacturers (i.e. Nike, Asics, Brooks) looking at current research?

Further Research Barefoot Running as a social phenomenon Differential diagnoses: 1.Bacterial and fungal infections (i.e. osteomyelitis) 2.Increased need for wound care education 3.Frostbite