There is a widespread belief among recreational athletes that running shoes play an important role in injury prevention by providing cushioning. Custom-fitted shoes and newer shoes are generally thought to provide better protection than older, less expensive shoes.

Surprisingly, scientific evidence points in the opposite direction.

Shoe type and knee forces during walking

Several studies have shown that cheap, flexible, flat shoes (e.g. flip-flops) reduce knee forces in patients with knee osteoarthritis [1-3]. The authors of these studies concluded that cheap, minimalist footwear is better than more expensive shoes for people with knee osteoarthritis.

Shoe selection and running injuries

There is a moderate amount of evidence relating to shoe use and incidence of running injuries [4], however, it is still an emerging field and many of the studies have looked at specific population subgroups such as army recruits or the elderly. It is therefore possibly too early to make general recommendations on shoe type. However certain trends do seem to be emerging.

A 2011 Cochrane Review compared running shoes that were individually custom fitted based on foot shape, with off the shelf running shoes and found no difference in the number of running injuries [4]. A study of Air Force recruits similarly found assigning custom running shoes based on foot shape had no effect on injury rates [5].

Another study compared custom-fitted running shoes based on a lower limb biomechanical assessment, with generic advice about running shoes and found no difference in injury rates between the two groups [6].

Newer running shoes create greater pressure on the sole of the foot, possibly because newer shoes are stiffer. Researchers recommend breaking new shoes in slowly and keeping old shoes a long time. The same researchers concluded that the chance of lower limb injury is greater with new running shoes [7].

Some authors have speculated that motion control shoes may have a bearing on the management of patellofemoral pain syndrome (PFPS), however there is no evidence to support a direct link between excessive rearfoot pronation and PFPS [8].

Barefoot or minimalist shoes

Barefoot running and minimalist shoes have both generated a lot of excitement and media interest over the last few years. Minimalist shoes have a sole that is thin, soft, flexible and flat and provides minimal or no support or cushioning.

Tibial (shin bone) and calcaneal (heel bone) movements do not appear to be different between running barefoot or in shoes. The variation between individual runners is much greater than any effect of running shoes. The authors of a 2000 study concluded that differences in bone movements are largely individual and not affected by shoe selection [9], however running shoes do produce higher joint forces at the knee and hip, compared to barefoot running [10].

Experienced barefoot runners produce lower ground collision forces than habitually shod runners [11]. Amongst experienced recreational runners, running barefoot or in minimalist shoes is associated with 70% fewer injuries, compared with running in traditional running shoes [12], although these figures are self-reported, so should probably be taken with a large grain of salt; further high-quality studies are required.

Transitioning to barefoot or minimalist shoes

Runners who normally wear cushioned shoes, training for a 10km event using minimalist footwear suffer more injuries. The best policy seems to be a cautious and gradual transition to barefoot or minimally shod running [13].

Shod running promotes a heel strike pattern, whereas unshod or minimalist running promotes a midfoot or forefoot strike (Fig. 1) [11, 14]. There are several other differences in gait pattern in barefoot running compared to shod running including higher stride frequency and greater requirement for muscular control through the lower limb to provide shock absorption [14].

Because changes in gait pattern and biomechanics will generally require strengthening of various tissues in the lower limb, a gradual transition to barefoot or minimally shod running should be made, over a period of at least 4-8 weeks, allowing time for gait retraining, and for strengthening exercises to produce a training effect (Figs. 2 and 3) [14].

Figure 2: Preparatory activities for barefoot running [14]

Figure 3: Suggested progression to barefoot running [14]
Conclusions

This is an emerging area of study and further research is required. Based on the evidence that is currently available, the following recommendations seem to represent the best general advice on running shoe selection.

Custom fitted shoes are not more effective than standard running shoes for preventing running injuries.
Minimalist shoes (soft, flexible-soled flat shoes with no support or cushioning) appear to be the safest type of shoe for running and walking.
Inexpensive shoes are just as good or better than expensive shoes.
In terms of safety and biomechanics, barefoot running, and running in minimalist shoes appear to be equivalent with each other, and both barefoot running and running in minimalist shoes are safer than running with expensive, custom-fitted shoes.
Transition to barefoot or minimalist shoes should be gradual over a period of at minimum 4-8 weeks and should include appropriate strengthening and gait adjustment drills to prevent too-much-too-soon type overuse injuries during the adaptation period.

References

1. Shakoor, N. and J.A. Block, Walking Barefoot Decreases Loading on the Lower Extremity Joints in Knee Osteoarthritis. Arthritis & Rheumatism, 2006. 54(9): p. 2923-2927.

2. Shakoor, N., et al., Effects of Common Footwear on Joint Loading in Osteoarthritis of the Knee. Arthritis Care & Research, 2010. 62(7): p. 917-923.

3. Sacco, I.C.N., et al., Joint Loading Decreased by Inexpensive and Minimalist Footwear in Elderly Women With Knee Osteoarthritis During Stair Descent. Arthritis Care & Research, 2012. 64(3): p. 368-374.

4. Yeung, S.S., E.W. Yeung, and L.D. Gillespie, Interventions for preventing lower limb soft-tissue running injuries. Cochrane Database Syst Rev, 2011. 7.

5. Knapik, J.J., et al., Effect on Injuries of Assigning Shoes Based on Foot Shape in Air Force Basic Training. American Journal of Preventive Medicine, 2010. 38(1, Supplement): p. S197-S211.

6. Schwellnus, M.P. and G. Stubbs, Does running shoe prescription alter the risk of developing a running injury? International SportMed Journal, 2006. 7(2): p. 138-153.

7. Rethnam, U. and N. Makwana, Are old running shoes detrimental to your feet? A pedobarographic study. BMC Research Notes, 2011. 4(1): p. 307.

8. Cheung, R.T.H. and G.Y. Ng, A systematic review of running shoes and lower leg biomechanics: A possible link with patellofemoral pain syndrome? International SportMed Journal, 2007. 8(3): p. 107-116.

9. Stacoff, A., et al., Tibiocalcaneal kinematics of barefoot versus shod running. Journal of Biomechanics, 2000. 33(11): p. 1387-1395.

10. Kerrigan, D.C., et al., The Effect of Running Shoes on Lower Extremity Joint Torques. Pm&r, 2009. 1(12).

11. Lieberman, D.E., et al., Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 2010. 463(7280): p. 531-535.

12. Goss, D.L. and M.T. Gross, Relationships among self-reported shoe type, footstrike pattern, and injury incidence, in U.S. Army Medical Department Journal. 2012. p. 25+.

13. Ryan, M., et al., Examining injury risk and pain perception in runners using minimalist footwear. British Journal of Sports Medicine, 2013.

14. Rothschild, C., Running Barefoot or in Minimalist Shoes: Evidence or Conjecture?