Isometric plank test

By performing this test the degree of lumbo-pelvic stability (Core) can be evaluated.

As pictured in illustration A, there are 4 variants of this test in which the level of difficulty is progressively increased.

1. Isometric plank.
2. Isometric plank on an unstable surface.
3. Isometric plank with leg extension.
4. Isometric plank with leg extension on an unstable surface.

• Required material: A flat surface, a stopwatch and some soft, unstable material (variants 2 and 4). The use of a mat is recommended for greater subject comfort during the test.

• Procedure: The subject should be in a prone plank position with both forearms resting on the floor, both legs extended in line with the spine and the hips in a neutral position. The arms must form a 90º angle at the elbow joint. This test measures the time the subject is able to remain in a stable position without compensations. The test ends when the hip descends or becomes in anteversion, accentuating the lumbar curve (hyperlordosis).

• Assessment: Measured in seconds (s). The subject has only one attempt. In variants 3 and 4, the same exercise will be repeated with each leg. The evaluator must be highly trained to identify changes or loss of control in the spine-pelvic region and terminate the test.

• Remarks: A strong and stable Core is the basis for all movement. On the other hand, a weak Core will pose a risk for the passive structures of the spine, and the vertebral discs can be greatly compromised by high impact exercises.