MINIMALIST / BAREFOOT RUNNING

Transcription

1 MINIMALIST / BAREFOOT RUNNING DR GAVIN SHANG SPORTS PHYSICIAN MBBCH (WITS) MPHIL SPORTS MED (UCT/SSISA)

2 BORN TO RUN BAREFOOT RUNNING Tarahumara Indians: Persistence hunting and thermo-regulatory advantage Ability to sweat negates reaching critical temperature Humans designed for barefoot endurance running Question: Are shoes abnormal/unnatural? Public theory: barefoot natural and therefore better Overhyped sensationalism Over simplification

3 INDUSTRY Multi-billion dollar industry selling marketed product(s) to reduce injury risk But, injury prevalence and incidence has not changed since 1970s

4 INDUSTRY (continued) Previously neutral shoes for normal arches, motion controlled for pes planus Now minimalist shoes to: reduce and prevent injuries run painfree and easier improve efficiency and performance generalization of one shoe (or in this case no shoe) fits everyone

5 VIBRAM Vibram USA Inc/Vibram FiveFingers LLC: (1) Strengthen muscles in the feet and lower legs (2) Improve range of motion in the ankles, feet, and toes (3) Stimulate neural function important to balance and agility (4) Eliminate heel lift to align the spine and improve posture (5) Allow the foot and body to move naturally

6 VIBRAM LAWSUIT Class Action Lawsuit (March 2012) deceptive and misleading statements about the benefits of barefoot running that could not be supported by science leading to increased injuries among runners who make the switch

7 TECHNIQUES POSE (forefoot) and CHI (mid-foot) techniques - Gravity assisted forward lean - Both show lower impact forces on joints (especially knee) EQUIPMENT: Minimalist/Barefoot runners vs. Shoe/Shod runners

8 TECHNIQUES (continued) Paula Radcliffe Haile Gebrselassie

9 HARVARD LAB Foot strike patterns and collision forces in habitually barefoot versus shod runners [doi: /nature08723] Daniel E. Lieberman, Madhusudhan Venkadesan, William A. Werbel, Adam I. Daoud, Susan D Andrea, Irene S. Davis, Robert Ojiambo Mang Eni, Yannis Pitsiladis Foot-strike pattern (heel, mid-foot or forefoot) Kinematic/kinetic variables (impact force, loading rate, joint angles)

10 HARVARD LAB (continued)

11 FINDINGS Barefoot shifts landing point to forefoot (more plantar flexed ankle on landing) Reduction in first impact force (impact transient) Decreased loading rate and peak impact force (3x lower in barefoot forefoot than shod heel-strike runners) Question: Less impact force = less injuries?

12 BAREFOOT HEEL-STRIKE

13 BAREFOOT HEEL-STRIKE (continued)

14 SHOD HEEL-STRIKE

15 SHOD HEEL-STRIKE (continued)

16 IMPACT TRANSIENT FORCE Impact transient force = 2.5x body weight within 50ms of ground contact Size of force associated with injury (tibial stress injuries) Running shoe heel cushioning concept: Absorb and decrease size of impact transient Reduce loading rate

17 IMPACT TRANSIENT FORCE (continued)

18 FOOT STRIKE HABITUALLY barefoot forefoot: no impact transient Results: smoother profile and significantly reduced loading rates and impact forces Impact peak absorbed by soft tissues, bones and joints (calf, ankle and Achilles tendon)

19 BAREFOOT FOREFOOT STRIKE

20 FOOT STRIKE (continued) Habitual shod runners = most heel-strike Habitual barefoot runners = most mid-foot or forefoot strike Lieberman: 83% of habitually shod runners were still heel-striking when barefoot running initially Impact transient is higher Impact loading rate 7x higher Higher impact forces + higher loading rates = greater injury risk Barefoot running not without risk or consequence

21 AMERICAN COUNCIL of EXERCISE ACE study: loading rates barefoot (blue) vs. Vibrams (purple) vs.normal running shoes (green)

22 ACE STUDY (continued) Forefoot strike runners (left) - loading rate lowest when barefoot forefoot Heel-strike runners (right) - loading rate highest when barefoot heel-strike - double that of shod heel-strike Vibrams lack heel cushioning of normal shoes and only marginally better than barefoot heel-strike ACE study: 50% still heel-striking (even 2wks into running with minimalist shoes)

23 INJURY Decrease injury risk with minimalist running? Adjust mechanics to forefoot strike, however, increased eccentric loading on plantar-flexed forefoot strike Change in loading pattern and load distribution in soft tissues unconditioned for barefoot running Leads to muscle fatigue and subsequent higher loading of soft tissues, joints and bones (muscle absorbs forces normally)

24 INJURY (continued) Number and nature of presenting injuries associated with minimalist runners has increased: - plantar fasciitis, Achilles tendinopathy, Achilles paratenonitis, calf strains, DOMS, bone stress injuries/fractures, medial tibial periostitis/periostalgia Question: more injuries associated with minimalist running because more people converting to minimalist running Swapped one set of injuries and injury patterns for another?

25 ISSUES Over-emphasis on strike pattern Land with heel strike = risk for injury due to lack of cushioning and higher impact forces Explicitly instructed to land on forefoot with minimalist shoes Achilles and calf related injuries commonly associated with barefoot running Do not force forefoot landing

26 ISSUES (continued) Practically difficult to start with low mileage for some Endurance runners (50-100km wks) will try maintain volume with minimalist shoes Impatience with compromise period leading to injuries Risk vs. reward of changing when benefit not guaranteed Will same perceived benefits/changes occur with more specified/ better training?

27 ISSUES (continued) Skill and technique to be learned Time for transition needed regardless of method (barefoot completely vs. gradual transition) Individualized adaptation to change in mechanics Incremental changes needed instead of wholesale changes Adapt positively or negatively (adaptors vs. non adaptors)

28 ISSUES (continued) Perceived benefits: Significant differences in muscle activation and loading patterns when running barefoot Possible positive biomechanical and neuromuscular changes from a new training stimulus

29 PRACTICAL BALANCE Theory sound but evidence lacking for both arguments for and against minimalist or shod running Education of public instead of over-exuberance related to marketing campaigns Common sense needed as well as scientific backing Further short and long term prospective studies needed Hype vs. science Sustainable niche vs. trending fad

30 VIBRAM UPDATE $3.75 million settlement Obliged to pay each customer (estimated 70 million people) partial refund of $94 on their purchase Reported likely payout between $20 and $50 Vibram no longer able to make beneficial claims in future advertising

31 RUNNING PERFECTION Responder and great barefoot/minimalist runner Non-responder and classic shod runner Somewhere in-between Ideal shoe somewhere in-between Is running the issue regardless of shoe or no-shoe? Exceeding threshold of adaptation as with all injuries

32 EXTREMES Maximalist shoes (Hoka One One) Antithesis to minimalist movement Great time to be a runner with many choices available: Stack heights Heel drop Arch support Material weight Pendulum swing to either extreme with everything inbetween