Track & Field (eBook)

1MAJOR TYPES OF MOTOR STRESS

In order to carry out optimal training, the following questions must be answered:

•Which factors have an effect that limits performance in specific sports?

•Which available measurements can accurately determine the current situation and the effects of training?

•Which training methods work best for individual athletes?

As a basis to answering these questions, Hollmann introduced the concept of major types of motor stress to training theory in 1967. These include:

•coordination,

•flexibility,

•strength,

•speed, and

•endurance.

Of course, there are smooth transitions and overlapping areas between these various categories. Nevertheless, a conceptual distinction is helpful to develop a precise understanding of factors which limit performance and specific training adaptations as well as the required training stimuli. In particular, specific factors pertaining to age and gender must be considered. A detailed presentation of the major types of motor stress and additional reference works can be found in Hollmann and Strüder (2009).

1.1COORDINATION

(Movement) coordination is defined as the interaction of the central nervous system (CNS; the brain and spinal cord) and the skeletal muscles within a specific sequence of movements. Intramuscular coordination (IC) refers to the interaction between nerves and muscles within a specific sequence of movements in a single muscle, while intermuscular coordination is the interaction of various muscles during a specific sequence of movements. The term technique is often used when coordination is meant during specific movements in sports. However, the individual technique specific to a sport is also limited by the other major types of motor stress. For example, the technical behaviour of a jumper during the flight phase depends significantly on the time available, which is determined by the vertical velocity of departure as a result of jumping strength.

The neuromuscular function provides the physiological basis for coordination. All muscle groups in the body are represented in the cerebral cortex. Voluntary movements are based on the integration of the motor and sensory system (see figure 2). Here, the cerebellum and the basal ganglia (a collection of nerve cell bodies) play an important role. In particular, the cerebellum receives sensory information and then modulates the temporal interaction and the direction of movements. The basal ganglia are primarily responsible for the regulation of movement speed. The brain stem and the motor nuclei in the thalamus control the functions of the cerebellum and the basal ganglia. This occurs in contrast to the motor part of the cerebral cortex, which initiates movements by planning which motor neurones (nerve cells) shall be used. A portion of the pre-frontal cortex, the pre-motor strip, is specifically used for the design of actions. From here, complex sequences of motor actions are controlled. The excitation of the motor centres in the cerebrum increases the impulses of the gamma system and prepares the pre-start state. This includes an increase in muscle tone (basic tension of the muscle) with a sensitivity increase of mechanoreceptors and proprioceptors. The latter include the muscle spindles, the Golgi tendon organs, and the joint receptors. This will allow smooth and properly dosed movements.

At the beginning of the motion sequence, the muscle spindles provide the target value of muscle length necessary to solve the motor task. In addition, the muscle spindles continuously measure the length of the muscle during movement execution. Only the simultaneous action in the antagonistic muscles allows for movements which are most finely graded in terms of force. The two muscle groups that enable movements in opposite directions at a joint are called agonists and antagonists.

The following factors are crucial for the quality of coordination:

•consideration of the physical laws that are relevant for the respective motion;

•degree of exercise of the agonist-antagonist muscles active during the respective motion; and

•adaptation state of the vestibular system (vestibular apparatus).

Depending on preliminary training as well as the type and frequency of stress on the muscle groups, the optimal level of coordination for each individual is reached at different ages. In men and women, movements which are not specifically trained may likely reach their individually optimal quality at about the age of 20. Accelerated growth and an early start of specific practice can lead to achieving an optimal level of coordination at a much earlier age. The more complicated the movements in a discipline, the more emphasis should be placed on starting coordination training as early as possible. If specific coordination exercises are started at an early age, optimal coordination can already be achieved by the age of 12 or 13. Disturbances in the longitudinal growth of young people (ratio of trunk to leg length), which during certain developmental phases are caused by accelerated growth and which have adverse effects on coordination, deserve special attention. Without special exercises there is a decline in the quality of coordination at old age. Improvement in the quality of coordination through practising the respective movement sequence is primarily achieved by facilitating (ingraining) the corresponding specific movement pattern. The better the quality of coordination, the more straightforward, effortless, and precise the movement goal is achieved. The movement sequences become more fluent and economic, and the superfluous luxury movements, typical for beginners, disappear. This leads to a decrease in energy expenditure and thus the demand for oxygen during a given muscular activity. Due to the...