7.8 Maximum Force, Range of Motion, and Joint Rotation
Maximum Force
Another biomechanical principle includes the concept of maximum force. Maximum force refers to an individual exerting maximum effort when completing a physical task. To achieve this, it takes more than just strength. Maximum force requires all possible joint movements that could contribute to the movement, using their full range of motion (ROM), and with appropriate sequencing.
Range of Motion (ROM)
Range of motion (ROM), while a factor of maximum force, is also a factor in movement efficiency and an indicator of flexibility. It can be defined as the measure through which a joint moves through its full movement potential, or movement at a joint from a position of full flexion to full extension.
Try This!
Test your own ROM by using either your hip or shoulder. When doing so, be sure to move gently, acknowledging any discomfort or movement that feels interrupted. These may be signs of obstructed range of motion due to anything from tight muscles, musculoskeletal injuries, or joint conditions.
Video: “7-Minute Hip Mobility Workout (Fix Tight Hips)” by nourishmovelove [8:41] is licensed under the Standard YouTube License.Transcript and closed captions available on YouTube.
Video: “10-Minute Shoulder Mobility Routine (Bulletproof Shoulders)” by nourishmovelove [9:48] is licensed under the Standard YouTube License.Transcript and closed captions available on YouTube.
Sequencing of Joint Rotation
The last of this chapter’s biomechanical principles is joint sequencing. In addition to ROM contributing to achieving maximum force, joint sequencing is required to make our movements as effective as possible. Sequencing of joint rotation refers to the idea that when attempting to achieve maximum force, the best possible strategy is to use joints specifically from large to small. What this means is rotating and utilizing joints which activate large muscles before moving onto small joints and muscles.
Movement in Action: Tennis Serve of Carlos Alcaraz
Video: “Carlos Alcaraz Serve in Slow-mo. It’s a thing of beauty. #tennis #serve #carlosalcaraz” by PlayYourCourt.com [0:24] is licensed under the Standard YouTube License. Music only.
Text Description
Consider what you see in this tennis serve:
- If you pause the video at 5 seconds, the athlete bends at the knees and hip slightly to jump; these are the larger joints which activate and utilize large lower leg muscles.
- Next, at 14 seconds, they extend their shoulder, bringing the racket up and then in front of their body. This movement utilizes slightly smaller muscles located in the upper back, shoulder, and chest.
- After that, at 17 seconds, they extend their elbow, which uses their triceps brachii muscle (an even smaller muscle), to bring the racket in contact with the ball.
- And finally, quickly after the 17-second mark, they flex their wrist using the flexors in their forearms (which are the smallest muscles in this example) during the follow-through movement of their serve.
Try This!
See for yourself how crucial the sequencing of joint rotation is to movement by trying this exercise at home.
Grab a rolled-up pair of socks and stand facing the direction you are going to throw them. This will act as our projectile (you are welcome to use a real ball; however, socks are the house-friendly option).
Complete the three throws using the following guidelines:
- Throw #1: Standing upright holding the socks, position your arm at a 90-degree angle with your upper arm parallel to the floor and your forearm perpendicular to it. Using only your wrist, throw the socks as far as you can (Hint: hold your opposite hand in front of your forearm if you cannot prevent your arm from moving as you throw). Record how far it went.
- Throw #2: Assuming a similar starting position, but now using your wrist and elbow joint, throw the sock as far as you can. Record how far it went.
- Throw #3: Assuming a similar starting position, but now using your wrist, elbow, and shoulder joint, throw the sock as far as you can. Record how far it went.
If done correctly, the throw attempts 1 to 3 should have increased in distance thrown. This is because each throw, aside from the first throw, used adding sequencing of joints compared to the previous throw.
“2.4 Human Dimensions and Joint Angles” from Biomechanics of Human Movement by Karine Hamm is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.
