Comparison of skin and shoe marker placement on metatarsophalangeal joint kinematics and kinetics during running.

This study investigated the effects of marker placement (skin- vs shoe-mounted) on metatarsophalangeal joint (MTP) kinematics and kinetics during running. Fifteen trained men ran on a 15-m track at 10 and 13 km/h with three (low, standard and high stiffness) shoe longitudinal bending stiffnesses (LBS). Reflective markers were fixed on the shoe upper, and on the skin using holes cut in the shoe. Three-dimensional marker positions and ground reaction forces were recorded at 200 and 2000 Hz, respectively. Kinematic and kinetic parameters were analyzed using one-dimensional metrics (statistical parametric mapping). MTP joint was less dorsiflexed at midstance ([57% to 100%] of braking phase and [0% to 48%] of pushing phase), and the MTP joint plantarflexion moment was higher ([22% to 55%] of pushing phase) with the shoe markerset in comparison with the skin markerset. The effect of LBS on MTP angle was found to be significant for a larger percentage of each stride using the shoe markerset compared to the skin markerset. However, the effect of LBS on plantarflexion moment was significant with the shoe markerset only. The effect of running speed on MTP angle was significant for a larger percentage of each stride with the skin markerset. This study demonstrates that the placement of markers influences the measurement of MTP kinematics and kinetics and that these effects are mediated by other variables such as LBS or running speed. It is concluded that the shoe markerset does not fully reflect the movement of the MTP joint.

Physiological and biological factors associated with a 24 h treadmill ultra-marathon performance.

The purpose of this study was to examine the physiological and biological factors associated with ultra-endurance performance. Fourteen male runners volunteered to run on a treadmill as many kilometers as possible over a 24-h period (24TR). Maximal oxygen uptake (VO(2max)), velocity associated with VO(2max)(VO(2max)) and running economy (RE) at 8 km/h were measured. A muscle biopsy was also performed in the vastus lateralis muscle. The subjects ran 149.2 ± 15.7 km in 18 h 39 ± 41 min of effective attendance on the treadmill, corresponding to 39.4 ± 4.2% of . Standard multiple-regression analysis showed that performance was significantly (R(2) = 0.82; P = 0.005) related to VO(2max) and specific endurance, i.e. the average speed sustained over the 24TR expressed in . VO(2max) was associated with a high capillary tortuosity (R(2) = 0.66; P = 0.01). Specific endurance was significantly related to RE and citrate synthase activity. It is concluded that a high VO(2max) and an associated developed capillary network are essential for ultra-endurance running performance. The ability to maintain a high %VO(2max) over a 24TR is another factor associated with performance and is mainly related to RE and high mitochondrial oxidative capacity in the vastus lateralis.