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Objectives: To investigate the impact of fast-start, steady or slow-start strategies of the running fraction in sprint triathlon on oxygen consumption, perception of fatigue and blood lactate.Design: Thirteen male triathletes (age; 36.4 ± 10.8 yy, height 174.8 ± 7.9 cm, body mass 70.6 ± 11.1 kg; V'O2max 62.4 ± 8.9 ml min-1 kg-1; mean ± SD) attended the laboratory five times in order to complete two incremental tests and three subsequent cycle-run sessions.Methods: Three experimental randomized sessions with different effort distribution were compared. The intensities of the 1st running kilometer were set at 95%, 100% and 105% of the second ventilatory threshold for slow, continuous and fast start protocol respectively. Measurement of ventilatory variables, blood lactate and ratings of perceived exertion were collected throughout all sessions.Results: A meaningful difference was found between the slow versus fast start protocol in V'O2 (SE = 0.58, P = 0.0005), BLa- (SE = 0.21, P = 0.0097), HR (SE = 1.23, P = 0.0011) and RPE (SE = 2.83, P = 0.0047) values. No differences in-between protocols were found at the end of the running bout whatever the condition.Conclusions: Differences in physiological parameters were found between protocols during the first kilometer, not at the end of exercise. The fast start appears to be more correct and useful for performance in racing setting and may be used as a strategy without impacting the remaining running bout in ecological setting. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate DNA damage in response to increasing bulks of aerobic physical exercise. Fifteen adult and trained athletes performed four sequential trials with increasing running distance (5-, 10-, 21- and 42-km) in different periods of the year. The γ-H2AX foci parameters were analyzed before and 3 h after the end of each trial. The values of all γ-H2AX foci parameters were enhanced after the end of each trial, with values gradually increasing from the 5- to the 42-km trial. Interestingly, a minor increase of γ-H2AX foci was still evident after 5- to 10-km running, but a much higher increase occurred when the running distance exceeded 21 km. The generation of DNA injury was then magnified by running up to 42-km. The increase of each γ-H2AX foci parameter was then found to be associated with both running distance and average intensity. In multivariate linear regression analysis, the running distance was significantly associated with average intensity and post-run variation in the percentage of cells with γ-H2AX foci. We can hence conclude that aerobic exercise may generate an acute DNA damage in trained athletes, which is highly dependent upon running distance and average intensity. [ABSTRACT FROM AUTHOR]

We examined whether the presence of fatigue induced by prolonged running influenced the time courses of force generating capacities throughout a series of intermittent rapid contractions. Thirteen male amateur runners performed a set of 15 intermittent isometric rapid contractions of the knee extensor muscles, (3s/5s on/off) the day before (PRE) and immediately after (POST) a half marathon. The maximal voluntary contraction force, rate of force development (RFDpeak), and their ratio (relative RFDpeak) were calculated. At POST, considering the first (out of 15) repetition, the maximal force and RFDpeak decreased (p<0.0001) at the same extent (by 22±6% and 24±22%, respectively), resulting in unchanged relative RFDpeak (p=0.6). Conversely, the decline of RFDpeak throughout the repetitions was more pronounced at POST (p=0.02), thus the decline of relative RFDpeak was more pronounced (p=0.007) at POST (-25±13%) than at PRE (-3±13%). The main finding of this study was that the fatigue induced by a half-marathon caused a more pronounced impairment of rapid compared to maximal force in the subsequent intermittent protocol. Thus, the fatigue-induced impairment in rapid muscle contractions may have a greater effect on repeated, rather than on single, attempts of maximal force production. [ABSTRACT FROM AUTHOR]

Acute changes in central control and peripheral properties of motor units following a half-marathon has never been examined in master athletes. Therefore, the main purpose of this study was to estimate the firing properties and twitch characteristics of motor units after a 21-km race in a group of ten trained older adults. High-density surface EMG decomposition was used to identify motor unit activity during a submaximal contraction of the tibialis anterior muscle before and after the half marathon. The area of the estimated motor unit twitch profile was found smaller after the race (P = 0.039). This reduction in contractile efficiency was compensated by a significant increase in the initial and average discharge rate of the identified motor units (P < 0.001). By estimating the amount of shared and independent synaptic input to tibialis anterior motor neurons, we demonstrated that adaptations in the discharge properties of master athletes' motor units are the likely consequence of an increased net excitatory synaptic drive to the motor neuron pool. These findings suggest a potential role of long-distance running in ameliorating declines in muscle function of older adults by enhancing the neural drive to muscle. [ABSTRACT FROM AUTHOR]