The aim of this study was to: (1) determine directly the energy cost of shuttle running (C Sh) and (2) compare it to the values indirectly estimated from kinematic data. C Sh over distances of ≈10 or ≈20 m was determined on 65 subjects (group 1) from gas exchange measurements over 155 trials, or indirectly estimated on 10 subjects (group 2) from the time course of the speed as follows. (1) The cost to accelerate from zero to peak speed was estimated assuming a 25 % efficiency and added to that of constant-speed running, as obtained on subjects of group 1. (2) Since (i) accelerated running on flat terrain is equivalent to running uphill at constant speed, on a slope dictated by the forward acceleration (di Prampero et al. in J Exp Biol 208:2809-2816, 2005), and (ii) the energy cost of running uphill is known, C Sh was obtained from the time course of the acceleration. C Sh increased with the average speed, at any given speed being significantly greater for the shorter distances; e.g., at ≈4 m/s over 10 m, it amounted to ≈14 J/(kg m), i.e., 3.5-fold larger than that at constant speed. The two indirect methods yielded results not significantly different from C Sh over the longer (≈20 m), but underestimated it over the shorter (≈10 m) distances. From our results, over ≈20 m C Sh can be obtained with sufficient accuracy from actual measurements of peak speed alone, thus, greatly simplifying the experimental procedure. The so-obtained data can then be utilized to assess the athletic status of any subject, as well as to plan appropriate training strategies.

2Rugby sevens is a rapidly growing sport. Match analysis is increasingly being used by sport 3 scientists and coaches to improve the understanding of the physical demands of this sport. This 4 study investigated the physical and physiological demands of elite men's rugby sevens, with special 5 reference to the temporal patterns of fatigue during match-play. Nine players, four backs and five

Our objective was to determine the effects of long-lasting endurance events on the energy cost of running (C(r)), and the role of maximal oxygen uptake (VO(2max)), its fractional utilisation (F) and C(r) in determining the performance. Ten healthy runners (age range 26-59 years) participated in an ultra-endurance competition consisting of three running laps of 22, 48 and 20 km on three consecutive days in the North-East of Italy. Anthropometric characteristics and VO(2max) by a graded exercise test on a treadmill were determined 5 days before and 5 days after the competition. In addition, C(r) was determined on a treadmill before and after each running lap. Heart rate (HR) was recorded throughout the three laps. Results revealed that mean C(r) of the individual laps did not increase significantly with lap number (P = 0.200), thus ruling out any chronic lap effect. Even so, however, at the end of lap 3, C(r) was 18.0% (P < 0.001) greater than before lap 1. In addition, a statistically significant acute lap effect on C(r) was observed at the end of the second and third laps (by 11.4 and 7.2%, respectively). The main factors determining performance were VO(2max), F, as estimated from the average HR, and the average C(r-mean) throughout the three laps; the grand average speed over the three laps being described by v (end-mean) = F × VO(2max) × C(r-mean)(-1). We concluded that (1) the substantial increase of C(r-mean) during the competition yields to marked worsening of the performance, and (2) the three variables F, VO(2max) and C(r-mean) combined as described above explaining 87% of the total competition time variance.

The aim of this study was to investigate: (1) the role of V · O2,max , the fraction of V · O2,max (F) and the metabolic cost of transport (CoT) in determining performance during an ultra-endurance competition and (2) the effects of the race on several biomechanical and morphological parameters of the lower limbs that are likely to affect CoT. Eleven runners (aged 29-54 years) participated in an ultraendurance competition consisting of three running stages of 25, 55 and 13 km on three consecutive days. Anthropometric characteristics, body composition, morphological properties of the gastrocnemius medialis, maximal explosive power of the lower limb and V · O2,max were determined before the competition. In addition, biomechanics of running and CoT were determined, before and immediately after each running stage. Performance was directly proportional to V · O2,max (r=0.77) and F (r=0.36), and inversely proportional to . Low CoT values were significantly related to high maximal power of the lower limbs (r=-0.74) and vertical stiffness (r=-0.65) and low footprint index (FPI, r=0.70), step frequency (r=0.62) and external work (r=0.60). About 50% of the increase in CoT during the stages of the competition was accounted for by changes in FPI, which represents a global evaluation of medio-lateral displacement of the foot during the whole stance phase, which in turn is associated with the myotendinous characteristics of the lower limb. Thus, lower CoT values were related to greater muscular power and lower FPI, suggesting that a better ankle stability is likely to achieve better performance in an ultra-endurance running competition. KEY WORDS: Maximal oxygen uptake, Ultra-marathon, Kinematics, Stiffness, Energy cost of running INTRODUCTIONMiddle-and long-distance running performance depends on several physical, physiological, biomechanical, metabolic, psychological and social factors (di Prampero, 2003;di Prampero et al., 1986). In particular, the three most important physiological factors determining high level performance are: (1) a large value of maximal oxygen uptake (V · O2,max , ml O 2 kg −1 min −1 ), (2) a large fraction (F, %) of V · O 2 ,max that can be sustained throughout the RESEARCH ARTICLEIndeed, strong correlations were found between V · O 2 ,max and running performance in heterogeneous-level runners (Billat et al., 2003;Maughan and Leiper, 1983). Additionally, several studies showed that, in elite distance runners, F, which is linked primarily to adaptations resulting from prolonged training (Holloszy and Coyle, 1984), is a crucial parameter to determine performance (Maughan and Leiper, 1983). Finally, at the metabolic intensity imposed by the product F×V · O 2 ,max , the running velocity is determined by the individual's ability to translate energy into performance (Daniels, 1985), i.e. to the energy expenditure per unit of mass and distance (CoT).CoT is generally expressed as the amount of energy spent above resting to transport 1 kg body mass (M b ) over a distance of 1 m. CoT is independent of...