Whenever a fitness trainer designs a resistance training program for a new client, a few basic principles are always applied in order for the training program to be effective.
Large to Small
When you are exercising, larger muscles should always be trained in the beginning and with more intensity and increased volume than smaller muscles.
High Skill to Low Skill
Exercises that involve a high level of dexterity and skill must be performed in the beginning when the concentration levels are higher. If you perform exercises that require you to maneuver accurately when yo are tired and fatigued in the latter half of a session, you increase the chances of injuring yourself.
Compound to Isolation
Exercises that involve a complex level of coordination of movement at more than joint e.g. squatting must be done before exercises that isolate only one joint such as leg extensions. If you perform isolation exercises in the beginning then you are obviously tiring yourself out when to comes to attacking complex exercises that require freshness and alertness.
Exercises that have increased importance or muscles in which we want the most improvements must be performed in the beginning when your mental energy is at your highest and fatigue is low so that exercises can be performed with the greatest intensity.
High Danger to Low Danger
Exercises where one is more prone to injury must be performed in the beginning when energy and concentration levels are highest. For example a one-rep max squat must be performed after a one-leg squat because a one-leg squat requires a greater degree of skill and concentration.
Core Muscles In the End
Muscles that stabilize the joints and especially the core muscles must be isolated only at the end of a workout and not before. The core muscles will be required throughout the span of a workout and if they become tired, then they are less likely to stabilize joints and can lead to injury.
If you stress a particular muscle (agonist) during an exercise, then it’s opposite muscle (antagonist) found on the other side of the joint must also be stressed in order to produce a similar increase in functional capacity (strength, endurance etc.). If there is imbalance in functional capacity and flexibility in opposing muscle groups across a joint then it can cause changes to posture and other forms of stress.
Although all these principles stated above cannot be fulfilled always, it pays for a trainer to remember these training principles in order to ensure the safety of the client and to maximize the effectiveness of a training program.