Nov 2013 Sport Speed Digest
NOV Digest_FINAL 2013
NOV Digest_FINAL 2013
Developing a complete training program for the 100-meter dash is a much more complicated task than meets the eye. At first glance, it appears that it is merely an all-out sprint as athletes attempt to reach maximum speed as fast as possible and maintain that speed throughout the race. In reality, the race involves five different phases, each requiring special training techniques.
Sprinting is a complex task that places a high neuromuscular demand on the performer and requires high levels of coordinated movement and appropriate sequencing of muscle activations to perform at peak levels. This paper will examine maximal velocity sprint mechanics with particular focus on the primary factors affecting performance, the mechanics associated with those factors, and the causal relationships that occur as a result of optimal sprinting mechanics.
In track and field athletics, sprint races cover a range of distances from 60m up to 400m. Under the International Amateur Athletic Federation (IAAF) rules such races start from a crouched position in blocks. There are three main types of crouched positions: the bullet, the medium and the elongated positions (Hay, 1993). A crouched start is more effective than a standing start as it places the sprinter in a position to move the centre of gravity rapidly well ahead of the feet and thus the runner must accelerate very quickly or else fall (Adrian & Cooper, 1995). The start, however, must not be thought of as a separate part of the whole race. It is an integral part of the total race and consequently is not distinct from the entire sprinting event.
Motion and interaction with the environment are fundamentally intertwined. Few people-tracking algorithms exploit such interactions, and those that do assume that surface geometry and dynamics are given. This paper concerns the converse
Sprinting is an activity that depends on the coordination of both nerves and muscles, and on the ability of the central nervous system to eliminate as many braking and friction movements as possible. Mechanically, sprinting is not a complex skill. Neurologically speaking, sprinting is complex sequence of firing by motor neurons to activate the muscles to move the human lever system in order to effectively apply force. A sprinter’s performance is mainly determined by the force and speed with which muscles can contract and relax and, because of the cyclic motion, the correct timing of the change from contraction (force application) to relaxation.
A running animal coordinates the actions of many muscles, tendons, and ligaments in its leg so that the overall leg behaves like a single mechanical spring during ground contact. Experimental observations have revealed that an animal’s leg sti¡ness is independent of both speed and gravity level, suggesting that it is dictated by inherent musculoskeletal properties. However, if leg sti¡ness was invariant, the biomechanics of running (e.g. peak ground reaction force and ground contact time) would change when an animal encountered di¡erent surfaces in the natural world.We found that human runners adjust their leg sti¡ness to accommodate changes in surface sti¡ness, allowing them to maintain similar running mechanics on di¡erent surfaces. These results provide important insight into the mechanics and control of animal locomotion and suggest that incorporating an adjustable leg sti¡ness in the design of hopping and running robots is important if they are to match the agility and speed of animals on varied terrain.
The vitamin and herbal supplement industry is big business in this country with annual sales exceeding $23 billion and involving over 40,000 products. A 15-year old law permits supplements to enter the market without the approval of the Food and Drug Administration (FDA). As a result, claims are often outrageously exaggerated and incorrect, and ingredients and product safety have not been determined. The FDA can act only after consumers become ill or a safety issue arises.
Coaches and athletes are well aware that the absence of efficient, tension- free muscular movement produces more rapid fatigue, poor performance, and increases the incidence of injuries. Executing short sprints in team sports also requires very efficient muscular coordination and relaxed movement patterns. During relaxed movement, less pliant tense muscles restrict range of motion and keep athletes from reaching their maximum mph speed.
The literature contains some hypotheses regarding the most favorable ground reaction force (GRF) for sprint running and how it might be achieved. This study tested the relevance of these hypotheses to the acceleration phase of a sprint, using GRF impulse as the GRF variable of interest. Thirty-six athletes performed maximal-effort sprints from which video and GRF data were collected at the 16-m mark. Associations between GRF impulse (expressed relative to body mass) and various kinematic measures were explored with simple and multiple linear regressions and paired t-tests.