The right foot forward, or the right shoe?

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

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

3. 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

4. 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

5. 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

6. 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 rearfootand 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

7. 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) • PeroneusLongus: increased activity, based on increased heel height, which everts the shod foot when put under inversion stress

8. 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.

9. 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

10. Discussion • Biomechanical model of barefoot gait • Forefoot strike at lateral forefoot. Preactivatedgastroc-soleus • Mild forefoot pronation followed by controlled heel contact and mild rearfootpronation • 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

11. 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?

12. 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?

13. 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