Open AccessEnergy cost of running and Achilles tendon stiffness in man and woman trained runners
Author(s) -
Fletcher Jared R.,
Pfister Ted R.,
MacIntosh Brian R.
Publication year - 2013
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.1002/phy2.178
Subject(s) - achilles tendon , medicine , stiffness , energy cost , ultrasound , zoology , tendon , running economy , physical therapy , surgery , mathematics , materials science , biology , composite material , architectural engineering , heart rate , vo2 max , blood pressure , engineering , radiology
The energy cost of running ( E run ), a key determinant of distance running performance, is influenced by several factors. Although it is important to express E run as energy cost, no study has used this approach to compare similarly trained men and women. Furthermore, the relationship between Achilles tendon ( AT ) stiffness and E run has not been compared between men and women. Therefore, our purpose was to determine if sex‐specific differences in E run and/or AT stiffness existed. E run (kcal kg −1 km −1 ) was determined by indirect calorimetry at 75%, 85%, and 95% of the speed at lactate threshold ( sLT ) on 11 man (mean ± SEM, 35 ± 1 years, 177 ± 1 cm, 78 ± 1 kg,V ˙ O 2 max = 56 ± 1 mL kg −1 min −1 ) and 18 woman (33 ± 1 years, 165 ± 1 cm, 58 ± 1 kg,V ˙ O 2 max = 50 ± 0.3 mL kg −1 min −1 ) runners. AT stiffness was measured using ultrasound with dynamometry. Man E run was 1.01 ± 0.06, 1.04 ± 0.07, and 1.07 ± 0.07 kcal kg −1 km −1 . Woman E run was 1.05 ± 0.10, 1.07 ± 0.09, and 1.09 ± 0.10 kcal kg −1 km −1 . There was no significant sex effect for E run or RER, but both increased with speed ( P < 0.01) expressed relative to sLT . High‐range AT stiffness was 191 ± 5.1 N mm −1 for men and 125 ± 5.5 N mm −1 , for women ( P < 0.001). The relationship between low‐range AT stiffness and E run was significant at all measured speeds for women ( r 2 = 0.198, P < 0.05), but not for the men. These results indicate that when E run is measured at the same relative intensity, there are no sex‐specific differences in E run or substrate use. Furthermore, differences in E run cannot be explained solely by differences in AT stiffness.