The aim of this study was to characterize the specifics of the sprint technique during the transition from start block into sprint running in well-trained sprinters. Twenty-one sprinters (11 men and 10 women), equipped with 74 spherical reflective markers, executed an explosive start action. An opto-electronic motion analysis system consisting of 12 MX3 cameras (250 Hz; 325,000 pixels) and two Kistler force plates (1000 Hz) was used to collect the three-dimensional (3D) marker trajectories and ground reaction forces (Nexus, Vicon). The 3D kinematics, joint kinetics, and power were calculated (Opensim) and were time normalized to 100% from the first action after gunshot until the end of second stance after block clearance (Matlab). The results showed that during the first stance, power generation at the knee plays a significant role in obtaining an effective transition, representing 31% of power generation in the lower limb, in the absence of preceding power absorption. Furthermore, the sprinter actively searches a more forward leaning position to maximize horizontal velocity. Since success during sprinting from the second stance onwards involves high hip and ankle activation, the above-mentioned three characteristics are specific skills required to successfully conclude the transition from start block into sprint running.

Limited scientific evidence suggests that physical activity is directly related to cognitive performance in patients with chronic fatigue syndrome (CFS). To date, no other study has examined the direct relationship between cognitive performance and physical fitness in these patients. This study examined whether cognitive performance and physical fitness are associated in female patients with CFS and investigated the association between cognitive performance and physical activity level (PAL) in the same study sample. We hypothesized that patients who performed better on cognitive tasks would show increased PALs and better performance on physical tests. The study included 31 women with CFS and 13 healthy inactive women. Participants first completed three cognitive tests. Afterward, they undertook a test to determine their maximal handgrip strength, performed a bicycle ergometer test, and were provided with an activity monitor. In patients with CFS, lower peak oxygen uptake and peak heart rate were associated with slower psychomotor speed (p < 0.05). Maximal handgrip strength was correlated with working memory performance (p < 0.05). Both choice and simple reaction time were lower in patients with CFS relative to healthy controls (p < 0.05 and p < 0.001, respectively). In conclusion, physical fitness, but not PAL, is associated with cognitive performance in female patients with CFS.

The aim of this study was to examine the physical characteristics and somatotype of junior and senior athletes in relation to sprint start and acceleration performance. Nineteen female junior, 23 male junior, 9 female senior, and 16 male senior sprint athletes performed three maximal 20‐m sprints. The starting blocks were instrumented to measure forward propulsion forces. Running velocity was measured by a laser positioned behind the athlete at 1 m height. Anthropometric measures were used to calculate somatotype and skeletal muscle mass. Body composition was estimated by underwater weighing densitometry. Junior and senior athletes were of similar height in both sexes. Male seniors were heavier, had larger limb circumferences, and a higher skeletal muscle mass than male juniors. Only the limb circumferences of the female seniors were larger than those of the female juniors. Female juniors were balanced ectomorphs, while female seniors were situated centrally on the somatochart (2.7–2.2–3.9 vs. 2.6–3.1–3.1; P=0.772, 0.047, and 0.066 respectively). Male juniors were mesomorphic ectomorphs, while male seniors were ectomorphic mesomorphs (1.8–3.3–3.6 vs. 1.6–4.2–2.8; P=0.148, 0.002, and 0.002 respectively). All sprint starts were similar for the junior and senior athletes of both sexes. Senior athletes accelerated more than the junior athletes, which resulted in higher running velocities after 5 m (senior vs. junior: females, 5.51±0.32 vs. 6.01±0.27 m · s^–1, P=0.001; males, 5.85±0.38 vs. 6.13±0.44 m · s^–1, P=0.043). The greater muscularity of senior compared with junior athletes did not result in better sprint start dynamics, but they did accelerate more and ran faster. These results show that late‐adolescent boys in particular are still developing their muscularity. The technical complexity of the sprint start and the negative influence of a higher body mass may partly explain the comparable sprint start dynamics of the junior and senior athletes. We suggest that strength training should be combined with sufficient attention to technical skills to allow a positive transfer.

The aim of this study was to relate the contribution of lower limb joint moments and individual muscle forces to the body centre of mass (COM) vertical and horizontal acceleration during the initial two steps of sprint running. Start performance of seven well-trained sprinters was recorded using an optoelectronic motion analysis system and two force plates. Participant-specific torque-driven and muscle-driven simulations were conducted in OpenSim to quantify, respectively, the contributions of the individual joints and muscles to body propulsion and lift. The ankle is the major contributor to both actions during the first two stances, with an even larger contribution in the second compared to the first stance. Biarticular gastrocnemius is the main muscle contributor to propulsion in the second stance. The contribution of the hip and knee depends highly on the position of the athlete: During the first stance, where the athlete runs in a forward bending position, the knee contributes primarily to body lift and the hip contributes to propulsion and body lift. In conclusion, a small increase in ankle power generation seems to affect the body COM acceleration, whereas increases in hip and knee power generation tend to affect acceleration less.