Background: As well as the anaerobic threeshold and 〖V ̇O〗_2 max, the running economy is an important variable in performance of long distance running. A recent study showed
significant relationships between the muscular balance of thigh muscles and the running economy in well trained female runners. Know it that, flexors (FL) and extensors (EXT) knee muscles endurance is
important for the maintenance of a good running mechanic and the FL and EXT hip muscles offers stabilization and propulsion movements. However, we don´t know whether there are relations between the
muscular balance of hip muscles and the running economy in well trained male runners. Thus, the purpose of this study was to evaluate the isokinetic muscular performance of the FL and EXT knee and hip
muscles and body composition and to verify associations of these variables with the running economy.
Methods: Were evaluated 9 well trained male runners aged 29,1 ± 6,5 years, 71 ± 9,6 Kg, 1,77 ± 0,1 meters and 〖V ̇O〗_2 max 61,51 ± 6,6. The running economy on flat (1% level grade at
11 Km/h) and on uphill (3% level grade at 10 km/h), the concentric and eccentric peak torque of FL and EXT knee (60/ºs and 240º/s) and hip muscles (60/ºs and 180º/s) and body composition were
evaluated. The conventional (FL concentric/ EXT concentric) and functional (FL eccentric /EXT concentric) ratio muscular balance were calculated for knee and hip muscles. The cost of running was
assessed through a gas analyzer (Quark CPET, Cosmed®, Italy) and a treadmill (Inbrasport, ATL, Brazil). The isokinetic evaluation was made in an isokinetic dynamometer (Biodex Medical System®,
Shirley, New York, EUA) and the body composition was performed through a dual energy x-ray absorptiometry (DXA Lunar DPX NT, GE Healthcare, New Jersey, EUA).
Results: The correlation results between the peak torque values of FL and EXT knee and hip muscles and the oxygen cost assessed on flat varied by 0.33 and 0.63 and, varied by 0.22 e
0.52 when the oxygen cost was evaluated on uphill. Only the muscular balance of hip muscles showed a significant inverse relationship between the functional muscular balance and the O2 cost on flat
and uphill, the values was -0.62 and -0.43. Likewise, the O2 costs on flat and uphill also were associated with the lean mass percentage (-0.85 e -0.72, respectively) and fat percentage (0,85 and
Conclusions: Higher muscular peak torque values of the lower limbs are associated with poor running economy, as well as the higher fat percentage. On the other hand, the high ratio
functional muscular balance of the hips and a high lean mass percentage are associated to better running economy. Although the correlation do not indicate causality effect, the results suggests that
lighter runners with less fat percentage and high levels of functional muscular balance are more likely to have better running economy values.