How Long Does It Last: 15, 30 or 60 Seconds of Stretching

The class runs a small experiment to see whether stretch duration changes the immediate gain in flexibility and how much of it remains after 10 minutes. It is measured with the sit-and-reach and the whole group's data is analyzed.

How to play

1. Pose the question and hypothesis, and split the class into three balanced groups: 15, 30 and 60 seconds per rep (4 min).
2. Shared 5-minute warm-up with easy jogging and dynamic mobility, the same for everyone (5 min).
3. Baseline sit-and-reach: two tries, record the better one (4 min).
4. Intervention: three reps of a seated hamstring stretch at each group's duration, with 15 seconds of rest between reps (5 min).
5. Measure right after and again 10 minutes later; in between, everyone walks and makes easy ball passes so the wait is the same (8 min).
6. Pool the data on the board or in a spreadsheet, calculate each group's average gain at both measurements and discuss the conclusion and its limits (4 min).

Rules

• All groups do the same warm-up and the same wait time so the comparison is fair.
• Stretches are held at 5 to 7 out of 10 in intensity, with no bouncing.
• Each student is always measured by the same person.
• Anyone with low back discomfort stretches with one knee bent and notes it on the sheet.

Variations

Adaptations

• Limited mobility: serves as data and timing lead or measures their own gain in a shoulder stretch.
• Visual impairment: the measurer reads the result out loud and a partner signals the start and end of each rep by touch.
• Hamstring injury: joins the measurement and analysis team.

Learning goals

• Apply the scientific method to a health and fitness question.
• Test the short-term effect of different stretch durations.
• Think critically about the limits of a school experiment.

Equipment for a class of 25

• sit-and-reach boxes: 3
• stopwatches: 6
• exercise mats: 28
• worksheets: 28

Teacher tip

Usually all three durations improve by a similar amount and part of the gain is gone at 10 minutes: a good moment to talk about short-term versus long-term effects.

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