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Key human anatomy and physiology principles as they relate to rehabilitation engineering
Published in Alex Mihailidis, Roger Smith, Rehabilitation Engineering, 2023
Qussai Obiedat, Bhagwant S. Sindhu, Ying-Chih Wang
To understand how movement occurs around any joint, we have to understand the different roles that muscles assume during a certain joint motion. The role of a muscle during a joint motion depends on several variables, such as the type of joint, direction of motion, and the amount of resistance to the motion. Changes in these variables will cause a change in the muscle's role. The different roles are agonist, antagonist, stabilizer, or neutralizer (Lippert 2006). An agonist is a muscle or group of muscles that is directly responsible for causing the motion. It is also known as the prime mover. Some muscles assist in a particular motion but are not as effective as the prime mover, those are referred to as assisting movers. In order to determine whether a muscle is a prime or an assisting mover, several factors must be considered including the muscle's size, the muscle's angle of pull, leverage, and the muscle's contractile potential (Lippert 2006). These factors will be discussed later in this chapter. An antagonist performs the exact opposite motion of the agonist for the same motion, which indicates that for the motion to occur, the antagonist should be relaxed when the agonist is working. In cases when both the agonist and the antagonist are working at the same time it will result in a co-contraction, which usually occurs when we try to perform a movement that needs to be accurate and precise. A stabilizer or a fixator is responsible for providing support or stabilizing body structures surrounding the joint in which the motion is taking place to allow the agonist to work more efficiently. Finally, a neutralizer is responsible for preventing unwanted motion, typically in muscles that can perform more than one action (Lippert 2006). In order to further understand these different roles, let us consider the following example. When performing a dumbbell biceps curls exercise (Figure 3.3), the agonist role is assumed by the biceps, and the triceps will act as the antagonist. The biceps brachii is responsible for both elbow flexion as well as forearm supination, and since only elbow flexion movement is desired in this exercise, the pronator teres muscle (pronates the forearm) will act as a neutralizer to counteract the supination of the forearm. Several muscles will act as stabilizers, including the deltoid muscle (stabilize shoulder) and trunk muscles.
Evaluation of physical workload during work behavior for work environment design from biomechanical perspective: a case study in initial orientation selection of work object for manual handling tasks
Published in Theoretical Issues in Ergonomics Science, 2021
Akisue Kuramoto, Kazuki Hiranai, Akihiko Seo
Figure 4 depicts the average of pMVC (apMVC) of the 3 s data of the work behavior step. At the trapezius, deltoid, and pronator teres muscles, the apMVC in the β = 45 condition was smaller than in the β = 0 condition. In addition, the average of pMVC at these muscles in the w = 1 condition increased up to 4% from that in the w = 0 condition. In the w = 1 condition, the average of pMVC for the pronator-teres muscle involved in the forearm rotation became the smallest in the β = 45 condition. At the biceps and the triceps muscles, there were no significant difference in the apMVC for the β conditions, and the apMVC was less than 5% in all conditions.