The Jump Test is a method to measure lower-limb muscle power, as well as coordination of lower and upper extremities, by jumping as high as possible. Jumping height is calculated from flight time.
The Jump Test was performed in 32,000 able Lifelines participants aged 8 years and older during 2A Visit 1 (section: physical state).

The 5-min jumptest is performed on a Chronojump Contactmat (40 by 60 cm) chronojump_manual.pdf.
Participants take off their shoes if the heels are higher than 2 cm. Research nurse asks the participant after any contraindications and makes sure the participant is able to make a two legged vertical jump.

Participant receives instructions:

• Standing in upright position, hands on the hips, feet slightly apart;
• Knees are flexed to an angle of 90° angle and jump as high as possible;
• Jump is performed fluently.

The research nurse demonstrates the jump at half speed. The participant first makes a test jump on half speed.
The participant makes 3 repeated vertical jumps, separated by a minimum of 30 seconds rest.
All flight times are recorded.

Participants could not participate in the Jump test if they were given the advice by a GP or specialist to not perform any pressurizing activities, for example after:

• Recent eye surgery (< 6 weeks)
• Recent thoracic-/abdominal surgery (< 6 weeks)
• Recent umbilical/incisional hernia surgery (< 6 weeks)
• Presence of umbilical/incisional/inguinal hernia
• Pneumothorax (< 6 weeks)
• Spontaneous pneumothorax (more than 2 times)
• Ribfracture
• Recent pulmonary embolism (2-6 weeks)
• Recent infarction (2-6 weeks)
• Recent cardiac catheterization (< 2 weeks)
• Aneurysm

… or if they should not perform any strenuous exercise for other reasons:

• Severe rheumatoid arthritis or osteoporosis
• History of vertebral fractures
• Hip-, ankle- or knee replacement

The gold standard for measuring countermovement jumps is with a force platform. The Chronojump was validated against a regular force platform in thirty recreationally active adults ¹⁾.
The Bland-Altman plot showed that Chronojump underestimated countermovement height by 5.46 cm. Previously it was shown that reliability was greater for participants more accustomed ot strength training.

Mechanography measures muscle power and peak-force, evaluates coordination and muscular function, and characterizes the muscle-bone relation.
The close functional relationship between muscle and bone observed throughout growth involves mechanical and biochemical crosstalk and suggests a prominent role of lean mass and muscle function on peak-bone acquisition. DXA scans can provide an accurate and precise quantification of lean mass, but do not provide information regarding muscle strength or quality.
Using a jumping-test-based mechanography, one can measure several parameters of muscular function and motion and also study the muscle-bone unit integrity. The loading imposed by muscles stimulates growing bones to adapt their geometry and mineral content to preserve, or increase, bone strength, which when impaired, predisposes to fracture (Frost’s mechanostat theory).
In elderly people, the mechanograph can be setup on its geriatric version based on the chair-rising test. The chair-rising test is a widely used measurement of lower body strength and falling risk in frail and elderly populations.
The machine is also very suited to measure muscle function and motion in children using the jumping plate. It also allows evaluation of the neuromotor function in both children and adults by measuring kinetic parameters where aspects such as equilibrium, coordination and proprioperception can be evaluated. ^{2) 3) 4)}

The following variables were collected during the Jump Test: