150722 Adaptation of bone to exercise part four of six

150722 Mechanical load consists of the following:

Bone is a connective tissue. When stressed it deforms under the load. Osteoblasts-bone growth cells- migrate to the surface of the bone to counteract the strain caused by this external weight. Because of this activity, bones grow stronger due to the bending, compressive, torsional loads, and the muscular contractions at the tendinous insertion points

Magnitude of force

  • Magnitude of the load density or the intensity of the load has to be above eighty to ninety percent of the one to ten repetition maximum in order to see tissue response improvements.

Speed of force development

  • The rate or speed of loading means how quickly the force is being applied to move the load in a concentric muscle contraction (force applied against a weight with the muscles shortening). Think speed during the lift.

The direction of forces

  • Varying the direction and pattern of movement will stress the bone and the attaching musculature. Full range of motion in all exercises ensures to a certain extent that the forces are applied as required.

The volume of force applied

  • The first three mentioned above are primarily responsible for bone mineral improvements. Typically, the total repetitions do not need to exceed thirty to thirty-five to see improvements IF the load is within the correct intensity zone (80%-90% 1-10RM).

Exercise prescriptions for bone growth stimulation[1]

Volume Ten reps for 3-6 setsLoad Moderate to heavy depending on your exercise experience
Variation  Undulating periodization pattern
Exercise selection  Structural, multi-joint, large muscle groups


The greater the magnitude or intensity, the higher and faster the power output, and the direction of force all contribute to the successful laying down of new bone growth.

[1] *Essentials of Strength Training and Conditioning

Baechle, T. R., Earle, R.W. Human Kinetics 2001

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