The Calf Endurance Heel Raise Test for Achilles: Single-Leg Rep Norms and Reinjury Risk Screening

An athlete comes back from an Achilles rupture or a stubborn bout of tendinopathy, passes the hop test, reports zero pain on the VISA-A questionnaire, and gets cleared. Four months later he is back in the clinic with the same tendon flaring up, or worse, a second rupture. The reason usually traces back to what got measured before clearance. Pain and hop distance recover early. Calf muscle-tendon endurance, the capacity to keep producing force over dozens of repeated contractions rather than one explosive one, lags behind by months, and almost nobody tests it before sending someone back to training.

The single-leg heel raise test fixes that blind spot. It is not a strength test in the one-rep-max sense; it asks the calf to keep producing near-full-range contractions until it genuinely cannot anymore, and the number it produces, especially compared side to side, tracks residual deficits that a pain-free gait and a decent hop will not reveal. Below is the standardized protocol, the scoring math, the norms worth knowing, and the specific rep and symmetry cutoffs tied to reinjury risk.

Why Rep Counts Catch What Pain Scores Miss

The Achilles tendon and the calf muscle-tendon unit it belongs to are built for repeated submaximal loading, not single maximal bursts. Walking, running, and jumping demand thousands of cyclic plantarflexion contractions per session, and a tendon or muscle that has been immobilized, surgically repaired, or chronically irritated loses endurance capacity well before it loses peak strength or the ability to tolerate one loaded contraction without pain. That is exactly why an athlete can clear a hop test, report a VISA-A score in the 90s, and still be sitting on a real deficit that only shows up once the calf fires 25 or 30 times in a row.

A single-leg heel raise to volitional fatigue exposes that deficit directly. It needs no lab equipment in its basic form, and unlike a hop test it produces a number, total repetitions, that most people can lose 10-20% of without ever noticing a change in daily walking. That sensitivity is the point of testing it separately from pain and strength.

Equipment and Setup

The standardized version uses a slight incline for a consistent, dorsiflexed starting ankle position on every rep, keeping the test comparable across sessions.

Test the uninjured side first as the baseline, then the involved side, with 2-3 minutes of rest between limbs.

Step-by-Step Testing Protocol

1. Position: Stand single-leg on the incline board, ball of the foot on the raised edge, knee straight, trunk upright, fingertips lightly touching a wall for balance only.
2. Familiarization: 3-5 submaximal reps at a controlled pace to confirm full range of motion before scoring begins.
3. Cadence: Set a metronome so each rep takes about two seconds up and two seconds down, a controlled tempo rather than a bouncing one.
4. Execution: Rise onto the ball of the foot to the same maximum height every rep, then lower under control to the starting dorsiflexed position, repeating continuously without pausing at the top or bottom.
5. Fatigue criteria: The set ends the first time any of these happens for two consecutive reps: heel-rise height drops below roughly two-thirds of the first three reps' height, the metronome cadence gets lost, the knee bends to compensate, or a hand takes real weight through the wall.
6. Recording: Log total completed reps before the fatigue criteria were met, plus peak height per rep if video or sensor data is available.
7. Repeat on the opposite limb after a full rest interval, then calculate the limb symmetry index below.

Total time per athlete runs 8-12 minutes. Healthy adults commonly need 20-35 reps to reach fatigue, so budget for a genuinely fatiguing set rather than a round number.

Scoring: Reps, Heel-Rise Height, and the Limb Symmetry Index

Total repetitions is the primary score, easiest to collect with nothing more than a metronome and a counter. Where equipment allows tracking heel-rise height per rep, work output, reps multiplied by average height, gives a more sensitive score, since a limb can grind out a similar rep count at a visibly shrinking range of motion, understating the real deficit if only reps get counted.

The limb symmetry index compares the involved side against the healthy side using either metric: LSI (%) = (involved-side score / uninvolved-side score) × 100. An athlete completing 18 reps on the surgical side against 24 on the healthy side posts an LSI of 75%. If that surgical side's average height also drops noticeably, the work-based LSI will typically read lower than the reps-based one, which is exactly the gap that matters: reps-only scoring can look better than the limb actually performs.

Score the uninvolved limb first every session and treat it as a moving reference, not a fixed chart number, since fitness fluctuation and detraining shift the healthy side's own baseline over a rehab timeline that can run six to twelve months.

What the Research Actually Shows

Hébert-Losier and colleagues (2017), publishing an updated reliability and normative-values study in Physiotherapy, tested 566 healthy volunteers aged 20-81 on the standing single-leg heel-rise test to fatigue on a 10° incline. Test-retest reliability was excellent (ICC = 1.0 both limbs), but the between-day limits of agreement told the more useful story: mean differences of 0.2 and 0.1 reps for right and left legs, with 95% limits of agreement spanning roughly -6 to +6-7 reps. In plain terms, a healthy, uninjured limb retested a week later can swing by 6-7 reps with zero real change in function. Males completed more reps than females overall, but that gap reversed after age 60, underscoring that one fixed cutoff across age and sex will misclassify people. The limitation: a normative study in people without Achilles pathology, establishing healthy variation rather than a post-injury deficit threshold.

Silbernagel and colleagues (2010), in Knee Surgery, Sports Traumatology, Arthroscopy, addressed that second question in 78 patients (mean age 42) following Achilles tendon rupture, tested at 6 and 12 months post-injury with a linear-encoder heel-rise work test capturing both reps and height. The work-based score, height times reps, detected side-to-side deficits a reps-only count missed: two patients with identical rep counts could have meaningfully different real calf function once shrinking range of motion was accounted for. The limitation is the population: a post-rupture surgical cohort, so its symmetry thresholds apply most directly to rupture rehab and more cautiously to tendinopathy or other reinjury-screening contexts.

Norms and Reinjury Risk Cutoffs

Two separate numbers matter, and conflating them is a common error: absolute reps show how a limb compares to healthy population norms, while LSI shows how the involved side compares to the athlete's own uninvolved side. Use both, but weight LSI more heavily in return-to-sport decisions, since it controls for individual baseline in a way a population norm cannot.

Treat the absolute-rep population data as context, not a cutoff: given the 6-7 rep between-day noise even in healthy limbs, a single session's rep count only becomes meaningful compared against the athlete's own uninvolved leg the same day. A reading of 22 reps means very little alone; 22 against an uninvolved side posting 30 that day, an LSI of 73%, means quite a lot.

Mistakes That Skew the Count

Using It in Return-to-Sport Decisions

Run this test at intake to establish a healthy-side baseline, then roughly monthly through mid-stage rehab, moving to every 2-3 weeks as the athlete approaches return-to-sport testing. A calf endurance deficit lingering below an 80% LSI while hop distance and pain scores look normal is one of the more common patterns behind athletes who clear conventional testing and still break down again, because the tendon and muscle have not rebuilt the repeated-loading capacity that running and jumping actually demand.

Do not let one test override this one, or this one override everything else. Pair it with hop testing, strength testing, and graded sport-specific volume, but give calf endurance the weight it deserves: it is one of the few field measures tied directly to the loading pattern that got the tendon injured, and one of the last qualities to fully normalize.