I am sure that many of you have already seen this study which is currently an Article in Press in the British Journal of Sports Medicine.
Whilst I have great respect for the authors and team involved, I am going out on a limb to say that I consider the title and conclusions of the paper highly misleading and potentially dangerous for the running public and the evidence base. I never like to see a controlled trial with a statement as the title, and this is a great example as to why.
Take Your Shoes off to Reduce Patellofemoral Stress When Running
Aim: Elevated patellofemoral joint stress is thought to contribute to the development and progression of patellofemoral pain syndrome. The purpose of this study was to determine if running barefoot decreases patellofemoral joint stress in comparison to shod running.
Methods: Lower extremity kinematics and ground reaction force data were collected from 22 trained runners during overground running while barefoot and in a neutral running shoe. The kinematic and kinetic data were used as input variables into a previously described mathematical model to determine patellofemoral joint stress. Knee flexion angle, net knee extension moment and the model outputs of contact area, patellofemoral joint reaction force and patellofemoral joint stress were plotted over the stance phase of the gait cycle and peak values compared using paired t tests and standardised mean differences calculated.
Results: Running barefoot decreased peak patellofemoral joint stress by 12% (p=0.000) in comparison to shod running. The reduction in patellofemoral joint stress was a result of reduced patellofemoral joint reaction forces (12%, p=0.000) while running barefoot.
Conclusions: Elevated patellofemoral joint stress during shod running might contribute to patellofemoral pain. Running barefoot decreases patellofemoral joint stress.
Original Source [1]
Yes, when comparing shod versus Barefoot runners in this study, peak Patellofemoral Joint Stress was 12% lower in the Barefoot Group, which was statistically significant. However, other kinematic variables were also significantly different, including stride length reduction (2.4%), stride cadence increase (2%), ankle dorsiflexion in mid-stance reduction (82%) and knee flexion angle in mid-stance change (4.2% higher in the shod group). This highlights the importance of reading and appraising a paper and not making do with the abstract.
This is where I consider the conclusions of this paper to be misleading. In my opinion (and with several colleagues in agreement), it is the change in these kinematic variables, as opposed to the removal of running shoes, that will have lead to the reduction in Patellofemoral Joint Stress.
As always, I am not interested in opinion; you must back up your argument with high quality evidence. So here it is:
Increasing Running Step Rate Reduces Patellofemoral Joint Forces
Purpose: Increasing step rate has been shown to elicit changes in joint kinematics and kinetics during running, and has been suggested as a possible rehabilitation strategy for runners with patellofemoral pain. The purpose of this study was to determine how altering step rate affects internal muscle forces and patellofemoral joint loads, and then to determine what kinematic and kinetic factors best predict changes in joint loading.
Methods: We recorded whole body kinematics of 30 healthy adults running on an instrumented treadmill at three step rate conditions (90%, 100%, and 110% of preferred step rate). We then used a 3D lower extremity musculoskeletal model to estimate muscle, patellar tendon, and patellofemoral joint forces throughout the running gait cycles. Additionally, linear regression analysis allowed us to ascertain the relative influence of limb posture and external loads on patellofemoral joint force.
Results: Increasing step rate to 110% of preferred reduced peak patellofemoral joint force by 14%. Peak muscle forces were also altered as a result of the increased step rate with hip, knee and ankle extensor forces, and hip abductor forces all reduced in mid-stance. Compared to the 90% step rate condition, there was a concomitant increase in peak rectus femoris and hamstring loads during early and late swing, respectively, at higher step rates. Peak stance phase knee flexion decreased with increasing step rate, and was found to be the most important predictor of the reduction in patellofemoral joint loading.
Conclusion: Increasing step rate is an effective strategy to reduce patellofemoral joint forces and could be effective in modulating biomechanical factors that can contribute to patellofemoral pain.
Original Source [4]
This paper identifies that a higher stride cadence, reduced stride length and thus reduced knee Flexion angle at mid-stance significantly reduces Patellofemoral Joint loading (14%), without manipulating the variable of footwear. We must however remember that both of these studies involved healthy runners and not subjects with Patellofemoral pain and we should exercise care when applying this data to this subgroup of patients.
That being said, Noehren et al (2011)[5] in BJSM proved that gait reeducation has a positive effect on subjects with Patellofemoral Pain and others have shown the positive effects that changing running biomechanics can have on joint loading as a whole (Brindle et al, 2013[2] & Heiderschiet et al, 2011[3] ). I expect there will be more studies along this route in the near future.
In conclusion, I think this study has a lot to offer the evidence base, just not in the fashion that the authors have concluded. Whilst I concede that removing footwear may be a way of inciting kinematic change when running, you can do it just as effectively with video analysis, metronomes, verbal cueing and functional drills. If you think that the cushioning or heel drop of your footwear is affecting your ability to initiate foot strike under your centre of mass, then you should strengthen your Gluteus Maximus and Hamstrings and improve your posture, dynamic pelvic positioning and swing phase mechanics, to start with.
So for now, clinicians and runners alike, don’t be duped into jumping on the barefoot bandwagon! Exercise some logic, as a middle ground of conscious gait reeducation and low-drop footwear is often more than adequate as a key part of the Patellofemoral rehab process.
References
[1] Bonacci et al (2013). Take your shoes off to reduce patellofemoral joint stress during running. BJSM. Article in Press.
[2] Bribdle et al (2013). Changing step width alters lower extremity biomechanics during running. Gait & Posture. Article in Press.
[3] Heiderscheit et al (2011). Effects of step rate manipulation on joint mechanics during running. Med Sci Sport Ex 43 (2), 296-302.
[4] Lenhart et al (2013). Increasing running step rate reduces patellofemoral joint forces. Med Sci Sport Ex. Article in Press.
[5] Noehren et al (2011). The effects of real-time gait retraining on hip kinematics, pain and function in subjects with patellofemoral pain syndrome. BJSM 45 691-696.
Last updated on March 2nd, 2021.
Completely agree, Brad.
For me, the poorly worded title and misleading conclusion is such a shame because the actual research isn’t bad at all. It certainly helps to confirm what many of us have been considering for a while now when working with PFJP clients in a clinical and coaching environment – that manipulating running kinematics though reeducating running form, can help to reduce PFJ stress. In particular increasing cadence, reducing the tendency to over stride, and as a biomechanical by-product reducing peak knee flexion in mid-stance.
Sure, taking ones shoes off and running barefoot can act as a stimulus encourage many of the kinematic changes. But let’s not forget what we know about knee and ankle loading during stance phase – we can’t just make load disappear, we just move the load from structure to structure through employing kinematic changes. Decreasing stress on the PFJ comes at the cost of increasing load elsewhere in the chain, most likely the (often ill-prepared) plantar flexor complex due to the increased ankle torque of an midfoot / forefoot strike. It’s a trade off, and one many runners fall foul of once inspired by a title such as that used in this research. Knee pain sorted, but replaced by [insert plantar flexor] injury.
Looking forward to Runners World magazine jumping onboard the barefoot bandwagon off the back of this title and conclusion, and of course the barefoot evangelists chipping in with their one-sided perspectives.
I’ll be using the insightful data from this study to reinforce the approach of finding a suitably low-drop (if appropriate, but not pre-requisite) shoe for the runner with PFPS and working with their existing running gait pattern to fine-tune elements such as cadence, tendency to over stride, posture, pelvic control, swing mechanics etc… to make achievable kinematic changes without demanding that they switch to barefoot running.
Indeed, sometimes barefoot running can be a useful coaching tool to promote desired changes in form – but it is exactly that – a coaching tool, not a long term solution. Coaches have been getting their athletes to do drills barefoot for years to encourage improved form – way before the term ‘barefoot running’ came with it’s current connotations.
Well summed up Brad. As both yourself and James say, not a bad piece of research when reading between the abstract and title, but needs to be put in context when looking at such papers as Lenhart et al (2013) as well as the multifaceted presentation of the runner in pain.
The need to look for quick solutions baffles me still. Sense will prevail……….i hope.
I agree with the findings that form is better than footwear. I would however like to see some proper studies done on raised heels effect with regards.
Muscle and tendon length and loading as well as effects on joints loading angles etc.
Domino effect of skeletal structure.
I agree, barefoot running is almost completely unpractical but having
retrained myself to run over the past 6 or 7 years I feel the heel to toe
differential in footwear is critical in the change in running form. A built up heel
has the effect of unloading the calf muscle when running with a ‘barefoot’ style
which is detrimental to efficiency and lessening impact forces. When you transition
to flats and then try to run with heels again, this is very noticeable and maybe something
that is not looked at to any great degree.
Great article, really well written.
Quick question, whilst instaneous patelofemoral loading reduces with increased cadence, do you think the increased number of steps and total volume of loading would still pose as an issue?
I no that you have provide some prelim research suggesting its favorability with the PFP population, but it doesn’t appear all that black and white.
What’s you experience???
Christian,
Apologies for the slow reply, thank you for a very intelligent question.
There is a study coming soon from the US (James and I discuss it in our recent podcast) that looks at exactly that and the answer presently is that cadence increase achievable in a human runner (I cannot recall the exact numerical ceiling) still reduces total ground reaction forces that a runner experiences, even though the number of foot contacts increases.
I hope that answers your question, I will post on the study when it is released to the open forum.
Brad