Yuto Miyake

Relationship between the length of the forefoot bones and performance in male sprinters

Although recent studies have reported that the forefoot bones are longer in sprinters than in non‐sprinters, these reports included a relatively small number of subjects. Moreover, while computer simulation suggested that longer forefoot bones may contribute to higher sprint performance by enhancing plantar flexor moment during sprinting, the correlation between forefoot bone length and sprint performance in humans has not been confirmed in observational studies. Thus, using a relatively large sample, we compared the length of the forefoot bones between sprinters and non‐sprinters. We also examined the relationship between forefoot bone length and performance in sprinters. The length of forefoot bones of the big and second toes in 36 well‐trained male sprinters and 36 male non‐sprinters was measured using magnetic resonance imaging. The length of forefoot bones in the big and second toes was significantly longer in sprinters than in non‐sprinters. After dividing the sprinters into faster and slower groups according to their personal best time in the 100‐m sprint, it was found that the forefoot bone length of the second toe, but not that of the big toe, was significantly longer in faster group than in slower group. Furthermore, the forefoot bone length of the second toe correlated significantly with the personal best time in the 100‐m sprint. This study supported evidence that the forefoot bones are longer in sprinters than in non‐sprinters. In addition, this is the first study to show that longer forefoot bones may be advantageous for achieving superior sprint performance in humans.

Applicability of ultrasonography for evaluating trunk muscle size: a pilot study

[Purpose] Ultrasonography (US) is widely applied to measure the muscle size in the limbs, as it has relatively high portability and is associated with low costs compared with large clinical devices such as magnetic resonance imaging (MRI). However, the applicability of US for evaluating trunk muscle size is poorly understood. This study aimed to examine whether US-measured muscle thickness (MT) in the trunk abdominal and back muscles correlated with MT and muscle cross-sectional area (MCSA) measured by MRI. [Subjects and Methods] Twenty-four healthy young males participated in this study. The MT and MCSA in the subjects were measured by US and MRI in a total of 10 sites, including the bilateral sides of the rectus abdominis (upper, central, and lower parts), abdominal wall, and multifidus lumborum. [Results] The interclass correlation coefficients of US-measured MT on the total 10 sites showed excellent values (n=12, 0.919 to 0.970). The US-measured MT significantly correlated with the MRI-measured MT (r=0.753 to 0.963) and MCSA (r=0.634 to 0.821). [Conclusion] US-measured MT could represent a surrogate for muscle size measured by MRI. The application of US for evaluating trunk muscle size may be a useful tool in the clinical setting.

The knee extensor moment arm is associated with performance in male sprinters

PurposeAlthough large knee extensor torque contributes to superior sprint performance, previous findings have indicated that the quadriceps cross-sectional area (CSA), a pivotal morphological regulator of knee extensor torque, is not correlated with performance in sprinters. We hypothesized that the knee extensor moment arm (MA), another main morphological regulator of knee extensor torque, may affect sprint performance. To test this hypothesis, we examined the relationship between knee extensor MA and sprint performance.MethodsThe quadriceps CSA and knee extensor MA in 32 well-trained male sprinters and 32 male non-sprinters were measured using magnetic resonance imaging.ResultsKnee extensor MA, but not quadriceps CSA, was greater in sprinters than in non-sprinters (P = 0.013). Moreover, knee extensor MA, but not the quadriceps CSA, was correlated with the personal best time in a 100-m race in sprinters (r = −0.614, P < 0.001). Furthermore, among 24 sprinters who participated in the 60-m sprint test, knee extensor MA was correlated with sprinting velocities in the acceleration (r = 0.717, P < 0.001) and maximum speed (r = 0.697, P < 0.001) phases.ConclusionThe present study demonstrates that the knee extensor MA is greater in sprinters than in non-sprinters, and this morphological structure in sprinters is associated with sprint performance. Therefore, for the first time, we provided evidence that a greater knee extensor MA in sprinters may be an advantageous for achieving superior sprint performance.

Relationship between Achilles tendon length and running performance in well-trained male endurance runners

This study aimed to determine the relationship between Achilles tendon (AT) length and running performance, including running economy, in well‐trained endurance runners. We also examined the reasonable portion of the AT related to running performance among AT lengths measured in three different portions. The AT lengths at three portions and cross‐sectional area (CSA) of 30 endurance runners were measured using magnetic resonance imaging. Each AT length was calculated as the distance from the calcaneal tuberosity to the muscle‐tendon junction of the soleus, gastrocnemius medialis (GMAT), and gastrocnemius lateralis, respectively. These AT lengths were normalized with shank length. The AT CSA was calculated as the average of 10, 20, and 30 mm above the distal insertion of the AT and normalized with body mass. Running economy was evaluated by measuring energy cost during three 4‐minutes submaximal treadmill running trials at 14, 16, and 18 km/h, respectively. Among three AT lengths, only a GMAT correlated significantly with personal best 5000‐m race time (r=−.376, P=.046). Furthermore, GMAT correlated significantly with energy cost during submaximal treadmill running trials at 14 km/h and 18 km/h (r=−.446 and −.429, respectively, P<.05 for both), and a trend toward such significance was observed at 16 km/h (r=−.360, P=.050). In contrast, there was no correlation between AT CSA and running performance. These findings suggest that longer AT, especially GMAT, may be advantageous to achieve superior running performance, with better running economy, in endurance runners.

Potential Relationship between Passive Plantar Flexor Stiffness and Running Performance

The present study aimed to determine the relationship between passive stiffness of the plantar flexors and running performance in endurance runners. Forty-eight well-trained male endurance runners and 24 untrained male control subjects participated in this study. Plantar flexor stiffness during passive dorsiflexion was calculated from the slope of the linear portion of the torque-angle curve. Of the endurance runners included in the present study, running economy in 28 endurance runners was evaluated by measuring energy cost during three 4-min trials (14, 16, and 18 km/h) of submaximal treadmill running. Passive stiffness of the plantar flexors was significantly higher in endurance runners than in untrained subjects. Moreover, passive plantar flexor stiffness in endurance runners was significantly correlated with a personal best 5000-m race time. Furthermore, passive plantar flexor stiffness in endurance runners was significantly correlated with energy cost during submaximal running at 16 km/h and 18 km/h, and a trend towards such significance was observed at 14 km/h. The present findings suggest that stiffer plantar flexors may help achieve better running performance, with greater running economy, in endurance runners. Therefore, in the clinical setting, passive stiffness of the plantar flexors may be a potential parameter for assessing running performance.

Specific adaptations of patellar and Achilles tendons in male sprinters and endurance runners

This study aimed to determine the impact of long‐term training on Achilles tendon (AT) and patellar tendon (PT) hypertrophy in sprinters and endurance runners. The cross‐sectional area (CSA) of AT and PT in 40 sprinters, 40 endurance runners, and 40 untrained subjects was measured using magnetic resonance imaging. The AT and PT CSAs were calculated at its proximal, middle, and distal portions. Three CSAs of AT and PT were averaged to give an overall absolute CSA for each tendon. To minimize the effect of body size on tendon CSA and obtain relative CSA, overall absolute CSA for each tendon was normalized with body mass. Absolute AT CSA did not differ significantly among all 3 groups. However, we found that relative AT CSA was significantly larger in endurance runners than in sprinters and untrained subjects (P < .001 for both). In contrast, both absolute and relative PT CSAs were significantly larger in sprinters than in endurance runners and untrained subjects (P ≤ .001 for all). These findings indicate that AT hypertrophy is characteristic of endurance runners, whereas PT hypertrophy is characteristic of sprinters. Therefore, we suggest that the AT and PT may undergo specific morphological adaptations in these athletes.

Relationship between knee extensor moment arm and long-sprint performance in male 400-m sprinters

The magnitude of the knee extensor moment arm (MA) may be a key morphological factor in achieving superior 100‐m sprint performance, potentially by enhancing maximal sprint velocity in sprinters. To further understand the advantage of a greater knee extensor MA in athletic events, we examined the relationship between knee extensor MA and long‐sprint performance in well‐trained 400‐m specialized sprinters. Twenty‐eight male 400‐m sprinters and 28 physical size‐matched male non‐sprinters participated in this study. Quadriceps femoris size, evaluated by anatomic cross‐sectional area (ACSA) and muscle volume (MV), and knee extensor MA were measured in participants using magnetic resonance imaging. The quadriceps femoris ACSA and MV, and knee extensor MA did not differ significantly between sprinters and non‐sprinters. In sprinters, quadriceps femoris MV, but not ACSA, and knee extensor MA were significantly correlated with their 400‐m personal best times. After adjusting for body height and/or body weight, it was found that significance remained only for knee extensor MA. These present findings suggest that in addition to 100‐m sprinting, the magnitude of knee extensor MA may be a key morphological factor in achieving superior long‐sprint performance in well‐trained 400‐m specialized sprinters.

Potential relationship between passive plantar flexor stiffness and sprint performance in sprinters

OBJECTIVE To investigate the relationship between passive planter flexor stiffness and sprint performance in sprinters. DESIGN Cross-sectional study. PARTICIPANTS Fifty well-trained male sprinters (age: 20.7 ± 1.9 years, height: 175.6 ± 4.9 cm, weight: 66.7 ± 5.1 kg) were participated in this study. Their best personal times in a 100-m sprint ranged from 10.22 to 11.86 s (mean, 11.12 ± 0.43 s). METHODS Passive stiffness of the plantar flexors measured using a dynamometer system. Passive stiffness during passive dorsiflexion was calculated from the slope of the linear portion of the torque-angle curve. RESULTS Plantar flexor passive stiffness was significantly correlated with personal best 100-m sprint time (r = -0.334, P = 0.018). CONCLUSION The present findings suggest that although the relationship between plantar flexor passive stiffness and personal best 100-m sprint time was relatively minimal, a higher plantar flexor passive stiffness may be a potential factor for achieving superior sprint performance in sprinters. Therefore, in the clinical setting, measurement of passive planter flexor stiffness may be useful for assessing sprint performance.

Association between Forefoot Bone Length and Performance in Male Endurance Runners

Recently, we reported that the forefoot bones were longer in sprinters than in non-sprinters, and that longer forefoot bones correlated with higher sprint performance in sprinters. To further understand the superiority of long forefoot bones in athletic performance, we examined whether forefoot bone length was associated with running performance in endurance runners. The length of the forefoot bones of the big and second toes were measured using magnetic resonance imaging in 45 male well-trained endurance runners and 45 male untrained subjects. After normalization with the foot length, it was found that the forefoot bones of the big and second toes were significantly longer in endurance runners than in untrained subjects (P<0.05 for both). Furthermore, longer forefoot bones of the big toe, but not of the second toe, correlated significantly with better personal best 5000-m race time in endurance runners (r=-0.322, P=0.031). The present findings demonstrated that forefoot bones were longer in endurance runners than in untrained subjects. These findings were similar to our findings for sprinters. In addition, we found that longer forefoot bones may be advantageous for achieving higher running performance in endurance runners.

Characteristics of lower leg and foot muscle thicknesses in sprinters: Does greater foot muscles contribute to sprint performance?

Abstract The present study aimed to determine the differences in thicknesses of the lower leg and foot muscles between sprinters and non-sprinters and to examine the relationship between these muscle thicknesses and sprint performance in sprinters. Twenty-six well-trained sprinters and 26 body size-matched non-sprinters participated in this study. Total 9 muscle thicknesses of bilateral lower leg and foot muscles in participants were measured using ultrasonography. Regarding the lower leg muscles, thicknesses of the tibialis anterior, gastrocnemius medial, and gastrocnemius lateral were measured. Regarding the foot muscles, thicknesses of the flexor digitorum longus, flexor hallucis longus, peroneal longus and brevis, abductor hallucis, flexor digitorum brevis, and flexor hallucis brevis were measured. Most muscle thicknesses were significantly larger in sprinters than in non-sprinters. The differences in mean thicknesses of both legs between the two groups were greater in the foot muscles, where it ranged from 10.2% to 17.1%, than in the lower leg muscles, where it ranged from −0.9% to 9.4%. Among foot muscles, the thickness of only the abductor hallucis was positively correlated with the personal best 100-m sprint time in sprinters (r = 0.419, P = 0.033), indicating that a greater abductor hallucis may be a negative factor for superior sprint performance. These findings suggest that although the foot muscles in addition to the lower leg muscles are more developed in sprinters than in non-sprinters, these muscle sizes may not contribute to achieve superior sprint performance.