Average Joe’s skeletal muscles are composed of a roughly equal number of slow-twitch and fast-twitch fibers. Some not-so-average people may display a clear dominance of fast fibers (or others of slow fibers) and therefore possess an innate talent to excel in fast and sprint-like sport events. There may have been evolutionary benefits from this striking heterogeneity in muscle typology within or between early human tribes. Yet, there appears to be significant clinical implications of these uneven muscle fiber type compositions in contemporary humans. Is speed a trade-off for insulin sensitivity? An elegant study by Blackwood et al (1) was recently published in this journal and demonstrates that insulin resistance is higher in an a priori established group of people with a dominant fast-twitch muscle fiber typology when compared to a slow-twitch group. This association between the heterogeneity in the skeletal muscle fiber typology of healthy adults and the whole-body insulin sensitivity means an important revival and expansion of earlier research. Lillioja et al (2) originally observed that the muscle fiber type composition is related to the in vivo insulin action in healthy men.