Running performance: foot power matters!

What they did

During the study, participants in both groups performed running training at their own level, training 3-5 times per week. Participants were asked to maintain a consistent intensity and volume of training throughout the duration of the study, using the Strava sports app, where the particular distance and level of intensity of the completed workouts were recorded. This training was monitored by researchers, who had access to the profile of each study participant.

The foot strengthening exercise group

In this group, all measurements were performed at baseline, after eight and 16 weeks. As mentioned above, for the first eight weeks, participants simply continued their running training as a control period. After that, they began the foot muscle exercises program, which lasted for eight weeks. The exercises were conducted barefoot and the protocol was performed every day, lasting approximately 30 minutes. Once a week, the training was conducted by a physiotherapist, who ensured that the exercises were being performed correctly. Every two weeks the program was progressed by incorporating more challenging exercises, as well as increasing the load and the number of repetitions. All the exercises were aimed at activating the internal foot muscles using simple standing posture and exercises on a stability disc. For a detailed breakdown on the foot-strengthening exercises used in the program (with illustrations), readers are directed to table 2 of the study.

The minimalist shoe group

In this group, all measurements were conducted four times: at baseline, and again after eight, 12 and 20 weeks. Like the group above, the first eight weeks was simply normal running to serve as a control period. Weeks 9-12 were a transition period where the runners were given time to adapt to the use of minimalist shoes. In this phase, the minimalist shoes were used for walking every day, starting with five minutes per day and ending up with one hour of walking. The period covering weeks 12-20 was the actual intervention phase; in the first week of this phase, participants ran in the Vibram minimalist shoes for the first 10 minutes, and then performed the rest of the training in their standard shoes. Each week, the time of running in minimalist shoes was extended by 5 minutes compared to the previous week, ending with 45 minutes of running in the last week. On non-running days, runners walked in the minimalist shoes for one hour. At the end of the 8-week intervention period, the final measurements took place.

What they measured

Remembering that the goal of the study was to see if higher levels of foot strength could increase running economy and allow runners to maintain a higher running speed before lactate-induce fatigue took hold, the baseline, pre-intervention (ie at 8 and 12 weeks respectively for the foot exercise and minimalist shoe group) and post intervention measurements consisted of the following:

·        La LT—lactate concentration associated with lactate threshold;

·        HR LT—heart rate associated with lactate threshold;

·        V LT—running velocity associated with lactate threshold.

Of these three measurements, V LT – running velocity associated with lactate threshold – was the key indicator, because as explained above, it is most closely correlated with maximum sustainable running velocity.

What they found

How did the runners respond to the foot strengthening interventions? Well, as might be expected, the first eight weeks of the study (when runners in both groups simply continued their running training as before) saw no significant gains in key markers of performance. However, after the 8-week training program, higher values of V LT (the maximum sustainable speed before the onset of rapid accumulation) were observed in both groups. In the foot-strengthening group, this improvement in V LT was significant, increasing from 10.14 to 10.74kmh (an increase of 5.92% - see figure 1).

In the minimalist shoe group, the improvements were not quite large enough to be considered significant; in this group V LT increased from 10.68 to 10.80kmh after the walking stage and to 10.88kmh after the running stage (an increase of 1.12% and 1.84% relative to the baseline speeds, respectively – figure 1). To determine whether these smaller improvements were really significant or had just occurred by chance, a repeat study using larger numbers of participants would be required. However, the authors of this study stated that in their opinion, these small improvements were unlikely to be a fluke because previous research has shown that switching from conventional running shoes to Vibram Five Fingers resulted in improved running economy, which was not just down to reduced shoe weight⁽¹²⁾. In addition, similar results (ie improvement in running economy) were observed in another study that investigated the effects of a 6-week transition from convention to minimalist running shoes⁽¹³⁾.

Figure 1: Effects of foot strengthening vs. minimalist shoe training on V LT

Recommendations for runners

Can stronger foot muscles lead to more efficient running resulting in higher maximum sustainable speeds? This research seems to answer that question with a firm yes! And remember that the participants were not elite runners but recreational runners, which suggests that most runners could benefit from foot strengthening. As to the best way of achieving more foot strength, this study indicates that performing specific exercises that target the foot muscles is more effective than resorting to the use of minimalist shoes. While minimalist shoes likely helped, the gains in running performance they produced were too small to be considered reliable. That said, it could be the case that over longer time periods of minimalist shoe training, these gains would become more significant. It might also mean that runners who principally use minimalist shoes for their training stand to gain less from a program of foot exercises (because their foot strength is already well developed).

If you are a recreational runner and are seeking better race performance, adding in some foot strengthening could be a great bet. Gains of nearly 6% in maximal sustainable speed are not to be sniffed at. That kind of improvement would knock around ten minutes off a 3-hour marathon! Foot strengthening could be especially useful for runners who are already undertaking a substantial volume of training and where adding in even more running training could lead to injury or burnout. The most effective way of achieving stronger foot muscles is to follow a specific strengthening program as shown in table 2 of the above study. However, if you’re the kind of person who struggles to follow indoor exercise programs, there’s always the option of adding in some minimalist shoe training instead. The caveat here is that this needs to be introduced carefully, and you shouldn’t expect the same magnitude of gains!

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