Testing strength, muscular endurance, power and flexibility

30 min

Force, repetitions, speed and range

Four components of fitness are about what muscles and joints can do. Strength asks how much force in one effort; muscular endurance, how many repetitions before tiring; power, how much force how fast; and flexibility, how far a joint can move. Each has simple school tests that need little more than a tape measure, a mat and a wall. The skill lies in running them the same way every time and in reading the results sensibly, for example by allowing for body mass.

Definition

Dynamometer: an instrument that measures force; a handgrip dynamometer reads the force of a squeeze, usually in kilograms.

Repetition: one complete movement of an exercise, such as one push-up.

Relative strength: strength divided by body mass, which allows fair comparison between people of different sizes.

Power: the rate of doing work, measured in watts (W); in jumping, it depends on both how high and how heavy the jumper is.

Range of movement: how far a joint can move from one end of its motion to the other.

The tests

Component	Test	Protocol in brief	Score
Strength	Handgrip dynamometer	Adjust the handle to the hand. Stand with the arm hanging by the side and squeeze as hard as possible for about 3 seconds. Three trials with each hand, a minute's rest between.	Best trial, in kg
Muscular endurance (upper body)	Push-ups	Body straight from head to heels; lower until the chest is about a fist's height from the floor, then push up to straight arms. Continue without resting until form breaks.	Number of correct push-ups
Muscular endurance (trunk)	Curl-ups in 60 s	Lie with knees bent at about 90° and feet flat, held by a partner; curl up until the elbows touch the thighs, then back until the shoulders touch the mat.	Correct curl-ups in 60 s
Power (legs)	Vertical jump	Mark the standing reach on a wall, then jump from both feet without a step and mark the highest point. Three jumps.	Best jump height, in cm
Power (legs)	Standing long jump	Feet behind a line, swing the arms and jump forward from both feet, landing on both feet.	Distance from the line to the back of the nearest heel; best of 3
Flexibility	Sit-and-reach	Shoes off, legs straight, feet flat against the box. Reach forward slowly with one hand on top of the other and hold the furthest point for 2 seconds. One practice, then two trials.	Best reach on the box scale, in cm

Power from a vertical jump. A heavier person who jumps as high as a lighter one has lifted more mass and so produced more power. Sayers and colleagues (1999) gave an equation for peak leg power $P$ , in watts, from jump height $h$ in cm and body mass $m$ in kg:

P = 60.7\,h + 45.3\,m - 2055

Rating (illustrative, ages 16 to 19)	Handgrip, boys	Handgrip, girls	Vertical jump, boys	Vertical jump, girls
Excellent	over 50 kg	over 32 kg	over 60 cm	over 50 cm
Good	42–50 kg	27–32 kg	50–60 cm	40–50 cm
Average	34–41 kg	22–26 kg	40–49 cm	30–39 cm
Below average	under 34 kg	under 22 kg	under 40 cm	under 30 cm

Illustrative ratings for teaching only. Real norms depend on age, sex, body size and population, and on the exact protocol and equipment.

Worked example

Worked example 1: jump height and power. Jean's standing reach is 228 cm and his best jump reach 273 cm; he has a mass of 60 kg. Paul jumps 40 cm and has a mass of 75 kg. Who is more powerful?

Jean's jump height: $273 - 228 = 45\,\mathrm{cm}$ .
Jean: $P = 60.7(45) + 45.3(60) - 2055 = 2731.5 + 2718 - 2055 = 3394.5\,\mathrm{W} \approx 3390\,\mathrm{W}$ .
Paul: $P = 60.7(40) + 45.3(75) - 2055 = 2428 + 3397.5 - 2055 = 3770.5\,\mathrm{W} \approx 3770\,\mathrm{W}$ .
Analysis: Jean jumps higher, but Paul lifts more mass and produces about 380 W more power. Jump height alone favours light athletes.

Worked example

Worked example 2: relative strength. Grace grips 38 kg and has a body mass of 60 kg; Diane grips 44 kg and has a mass of 80 kg.

Grace: $\frac{38}{60} = 0.63$ kg of grip per kg of body mass.
Diane: $\frac{44}{80} = 0.55$ .
Diane is stronger in absolute terms; Grace is stronger for her size. For a climber or gymnast, who must move their own body, relative strength matters more.

Worked example

Worked example 3: measuring progress. After six weeks of training, a pupil's push-ups rise from 18 to 24.

Increase: $24 - 18 = 6$ push-ups.
Percentage improvement: $\frac{6}{18} \times 100 = 33\%$ .
Before claiming the training worked, check the retest followed the same protocol: same depth, same tester, no rests, same time of day. A change in the rules can look like a change in fitness.

Tip

Same rules, same judge. Push-ups, curl-ups and the sit-and-reach depend on the tester's judgement of form. Agree the standard of a correct repetition before testing, and have the same partner count at the retest.

Warning

Safety and common mistakes. Warm up before jumping and stretching tests. Never bounce in the sit-and-reach: reach slowly and hold. Do not hold your breath while squeezing the dynamometer. Stop push-ups when form breaks, rather than counting sagging repetitions. Remember that a long reach in the sit-and-reach also depends on arm and leg length, not only flexibility.

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Practice

Name one test each for strength, muscular endurance, power and flexibility.
Describe how to score the standing long jump.
A pupil's standing reach is 215 cm and best jump reach 252 cm. Find her jump height.
Use the Sayers equation to find the peak power of a 58 kg athlete who jumps 42 cm.
Find the relative grip strength of a 70 kg boy who grips 49 kg.
A pupil's curl-ups fall from 40 to 35 after a month of illness. Calculate the percentage change and name the training principle that explains it.
Why is a practice trial given before the sit-and-reach?
A coach ranks his volleyball players by vertical jump height only. Evaluate this, using Worked example 1.

Show answersHide answers

Strength: handgrip dynamometer. Muscular endurance: push-ups or curl-ups. Power: vertical jump or standing long jump. Flexibility: sit-and-reach.
Measure from the take-off line to the back of the heel nearest the line; take the best of three jumps.
$252 - 215 = 37\,\mathrm{cm}$ .
$60.7(42) + 45.3(58) - 2055 = 2549.4 + 2627.4 - 2055 = 3121.8\,\mathrm{W} \approx 3120\,\mathrm{W}$ .
$\frac{49}{70} = 0.70$ kg per kg of body mass.
$\frac{35 - 40}{40} \times 100 = -12.5\%$ , a fall of 12.5%. Reversibility: fitness is lost when training stops.
The first reach acts as a warm-up and is usually shorter; a practice trial makes the recorded scores more reliable.
For volleyball, jump height (how high the hands reach) matters directly, so it is a valid measure of jumping performance. But it is not a measure of power, which also depends on mass, and players' standing reach differs too; the coach should also consider total reach (standing reach plus jump height) and skill.

Remember

Strength: handgrip, best of 3 in kg. Endurance: push-ups, curl-ups in 60 s.
Power: vertical jump (jump reach − standing reach), standing long jump.
Sayers: $P = 60.7 h + 45.3 m - 2055$ .
Flexibility: sit-and-reach, slow and held, after a practice trial.
Use relative scores when body size differs.

Sources and credits

Sayers SP, Harackiewicz DV, Harman EA, Frykman PN and Rosenstein MT, "Cross-validation of three jump power equations", Medicine and Science in Sports and Exercise 31 (1999) 572–577.
G. Gregory Haff and N. Travis Triplett (eds), Essentials of Strength Training and Conditioning, 4th edition, National Strength and Conditioning Association, Human Kinetics, 2016: test protocols, summarised.
Photo: Hand dynamometer, Ashashyou, Wikimedia Commons, CC0.
Vertical jump diagram, test table, illustrative norms, worked examples and practice: written by Ganzaa.

1Force, repetitions, speed and range

2The tests

Force, repetitions, speed and range

The tests