Plank Test by Age — Scoring and Norms

The plank test scores one thing: how long the trunk stabilizers hold a straight line before the line breaks. Enter your hold in seconds — the clock stops at form failure, not at exhaustion.

How to run it

1. Forearms and toes on the floor, elbows stacked directly under the shoulders.
2. Head, hips and heels in one line. Brace the abdominal wall; do not let the hips ride up into an inverted V or drift toward the floor.
3. Time from the moment the position is set until alignment visibly breaks. Shaking is normal and is not a stop signal — a lost line is.

What the research norms actually say

The reference study behind this scale is Strand and colleagues, 2014. It is a good study to know the shape of, because most plank charts online cite it for numbers it never published.

What it did publish: 471 college students — 194 men and 277 women, average age about 20 — held a prone forearm plank to volitional or technique failure. Men averaged 124 seconds (SD 72) and women 83 seconds (SD 63). Athletes averaged 123 seconds against 83 for non-athletes. Training three or more times a week was the threshold at which habitual activity started to matter, with the largest effect above five times a week.

Two limits follow directly. The sample is college-age, so the percentiles are not an adult lifespan norm; and the standard deviations are more than half the means, which tells you the distribution is wide and skewed. The paper itself says further work is needed before generalizing to other populations.

The five bands this calculator prints — roughly under 15 seconds, 15 seconds to 1 minute, 1 to 2 minutes, 2 to 4 minutes, and beyond 4 minutes — are a practical field scale layered on top of that literature, not percentiles lifted from the paper. Treat them as coarse.

The age-graded plank standard that does exist

If you came looking for a by-age chart, the real one in U.S. use is military. The Navy dropped curl-ups from the Physical Readiness Test in March 2021 and replaced them with a scored forearm plank, on Naval Health Research Center advice that “the forearm plank is a better test of core strength and abdominal muscular endurance” and that “the repeated spinal flexion movement of the curl-up is not operationally relevant, may aggravate lower-back injuries and does not appropriately challenge the abdominal musculature.”

The structure of that scale is worth borrowing even if the exact times are not yours to use:

• It is graded by age bracket, stepping down five seconds per bracket. As published with the 2020 announcement, the top “outstanding” time ran 3:40 for ages 17–19, 3:10 for 45–49 and 2:50 for 65 and over — a total swing of 50 seconds across roughly five decades.
• It applies the same times to men and women in every bracket, which is the opposite choice from the research norms above.
• Standards get revised. Check the Navy’s current PRT guidance before treating any specific time as today’s requirement.

Why form beats the stopwatch

A plank held with the hips sagging has shifted load off the abdominal wall and onto the lumbar spine and passive tissue. The number goes up; the thing you were measuring goes down. Stopping at alignment failure feels like it costs you seconds — it is what makes the seconds mean anything, and it is the criterion both the research protocol and the military test use.

The federal guidelines list planks by name among the body-weight activities that satisfy the muscle-strengthening recommendation of at least 2 days a week, alongside push-ups and pull-ups. Train them; test them occasionally.

Pair this with the push-up test for upper-body endurance and the sit-up test for the movement the Navy replaced, or go back to the full fitness test calculator.

This content is informational and does not replace evaluation by an exercise professional.