To move in an organized and efficient manner, the HMS must have precise control over its collective segments. This segmental control is an integrated process involving neural, skeletal, and muscular components to produce appropriate motor responses. This process – and the study of these movements – is known as motor control and focuses on the involved structures and mechanisms used by the central nervous system to integrate internal and external sensory information with previous experience to produce a skilled motor response.
Motor control is concerned with the neural structures involved in motor behavior and how they produce movement (Coker, 2004; Nordin et al., 2017; Roos, 1997; Schmidt & Wrisberg, 2000). Essentially, motor learning and development are required for an individual to have proper motor control. Fitness professionals play a key role in the development of their clients’ motor control through proper instruction during exercise and fitness efforts.
MUSCLE SYNERGY
One of the most important concepts in motor control is that muscles are recruited by the nervous system in groups, known as muscle synergy (Newton, 2003; Roos, 1997; Singh et al., 2018). There is never a time when just one muscle is activated alone. This makes controlling movement more efficient by allowing muscles and joints to function as functional units (Bizzi & Cheung 2013).
Muscle synergy represents the internal relationship between agonistic and synergistic muscle roles for a given movement pattern. Through the practice of proper training technique and format, these synergies become more fluid and automated. Table 7-3 examines muscle synergy for some common gym exercises.
Exercise | Synergies between muscles |
|---|---|
| Squat | Agonists: quadriceps, gluteus, maximus Synergist: hamstring complex Stabilizer: transverse abdominis |
| Shoulder press | Agonist: deltoids Synergist: triceps brachii Stabilizer: rotator cuff |
| Bench press | Agonist: pectoralis major Synergists: triceps brachii, anterior deltoid Stabilizer: rotator cuff |
| Seated row | Agonist: latissimus dorsi Synergists: posterior deltoid, biceps brachii Stabilizer: rotator cuff |
PROPRIOCEPTION
Mechanoreceptors collectively feed the nervous system with a form of sensory information known as propioception. Proprioception uses information from the mechanoreceptors (i.e. muscle spindles, Golgi tendon organs, and joint receptors) to provide information about body position, movement, and sensation as it relates to muscle and joint strength (Newton, 2003). Proprioception is an essential source of information that the nervous system uses to gather information about the environment to produce the most efficient and accurate movement.
For example, proprioceptive input can signal a runner to contract the ankle muscles to prevent an inversion injury. Research has shown that although proprioception can help prevent injury, it is altered after injury. This means that many of the current health club members have altered proprioception due to previous injuries. This provides a rationale for incorporating both core and balance training to improve one’s proprioceptive abilities.
SENSORY-MOTOR INTEGRATION
Sensorimotor integration is the ability of the nervous system to collect and interpret sensory information and to select and execute the appropriate motor response (Biedert, 2000; Drury, 2000; Janda & Va Vrova, 1996; Levangie et al., 2019; Rose , 1997). The definition implies that the nervous system ultimately dictates movement. It is important to recognize that the function of the nervous system includes both the central and peripheral nervous systems, as well as their integration with the musculotendinous structures and inert tissues (ligament and capsule).
For example, during an exercise the muscle is activated and movement takes place. Movement occurs as a result of neural input to the muscle from the nervous system. Further to this point, the movement that occurs can activate the muscle receptors and the receptors in the joint itself, both providing feedback to the nervous system and influencing the movement.
Sensorimotor integration is effective as long as the quality of incoming sensory information is good (Janda & Va Vrova, 1996; Levangie et al., 2019). Individuals who train using improper form will develop incorrect sensory information delivered to the central nervous system, leading to movement compensations and possible injury. It is therefore important to create well-designed exercise programs and encourage clients to exercise with the correct techniques at all times. For example, if an individual consistently rounds and raises the shoulders during a chest press performance, this can lead to altered muscle length-tension relationships, altered force-torque relationships, and altered arthrokinematics, ultimately leading to shoulder injury.