The effects of marathon running on various foot muscles are shown in a new study.

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WWith the rise in fitness awareness, more people are include long-distance running in their training routine. Additionally, they take part in several regional, international, and local marathons. However, marathon running can cause foot muscle injury and muscular exhaustion, which in turn can cause injuries or persistent discomfort. Little is known about how running marathons affects the various foot muscles at the moment.n

In general, foot muscles can be classified as intrinsic or extrinsic muscles. Extrinsic muscles begin in the lower leg and insert into the foot via the ankle, whereas intrinsic muscles originate and insert within the foot. It has been difficult to connect long-distance running to the lowering of the longitudinal arch thus far.

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The detrimental consequences of full marathon running on the intrinsic and extrinsic foot muscles are now the subject of a new study, which also examines how these effects are related to alterations in the longitudinal foot arch. Ayako Higashihara, Takayuki Inami, Kento Nakagawa, from Waseda University, Takaya Narita, from Toin University of Yokohama, and Professor Mako Fukano from Shibaura Institute of Technology (SIT) were all members of the study team. The Scandinavian Journal of Medicine & Science in Sports has published its results.n

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22 college runners who ran at least twice a week and have signed up for the full marathon at the Mt. Fuji International Marathon in either 2019 or 2021 were recruited for the research via track and field clubs. Prior to the marathon and 1, 3, and 8 days after the full marathon, the researchers measured the participants’ intrinsic and extrinsic foot muscles’ transverse relaxation time (T2) using magnetic resonance imaging (MRI), which is a measure of muscle damage.nnnn

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T₂ is defined as the time taken by the transverse magnetization vector in an MRI to decay to approximately 37% of its initial value, and is influenced by tissue-specific characteristics.n

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The intrinsic muscles studied included the abductor hallucis (ABH), flexor digitorum brevis (FDB), and quadratus plantae (QP) and the extrinsic muscles included the flexor digitorum longus (FDL), tibialis posterior (TP), and flexor hallucis longus (FHL). The researchers also determined the longitudinal foot arch height via three-dimensional analysis of foot posture for 10 of these participants at the same time intervals as the T₂ MRI to determine the changes in longitudinal foot arch height.

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On comparison with the values of T₂ before the marathon, the researchers observed that the T₂ values of QP, FDL, TP, and FHL significantly increased one day after the marathon, and varied throughout the observation period. Further, they also found that increase in T₂ of TP persisted three days after the marathon. However, they did not observe any major difference in T₂ for ABH and FDB.n

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The team also did not find any significant changes in the toe flexor muscle strength in any of the participants. Interestingly, they also noted that the arch height ratio statistically decreased from pre-marathon to 1 and 3 days after the race, and this change could be correlated with T₂ changes in FDL and FHL.n

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“These results indicate that the damage and recovery response after a full marathon differs among the various foot muscles. For our research participants, all three extrinsic muscles and only one intrinsic muscle showed damage after marathon running, suggesting that extrinsic muscles could be more susceptible to marathon-induced damage than the intrinsic ones,” explains Prof. Fukano.n

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This prominent damage to extrinsic foot muscles reflects the extensive pressure borne by the ankle joint while running for long-distances as compared to the rest of the foot—something other studies have also shown. Since QP is attached to FDL and/or FHL, it may also have a secondary function in running, along with extrinsic foot muscles, making it the only intrinsic foot muscle to get damaged by marathon running. Furthermore, the correlation between FDL and FHL and the longitudinal foot arch height indicates that marathon-induced damage to these extrinsic muscles could be a factor in decreasing the foot arch height.n

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“Since more people are now running for their fitness, our findings can provide runners and sports professionals insights on planning better recovery strategies focusing on muscle fatigue and damage to prevent running-related injuries and also improve runners’ conditioning,” concludes Prof. Fukano.

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n Provided by
n Shibaura Institute of Technology

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