Isometric exercise and pain in patellar tendinopathy, a pre-registered crossover replication of Rio 2015
One session of 5 × 45-s quadriceps holds at 70% MVIC was no better than dynamic leg extensions: pain on the decline squat fell only 0.9 of 10 across both, had drifted back by 45 min, and 4 of 20 responded to the holds
Holden and colleagues re-ran the single-session comparison of Rio 2015 (REF-627) in a larger, more varied sample with a pre-registered protocol.
Twenty-one adults with ultrasound-confirmed patellar tendinopathy (41% women, median symptom duration 24 months) did one session of heavy isometric quadriceps holds (5 × 45 s at 70% MVIC, knee at 60 degrees) and one session of dynamic leg extensions (3 × 8 at the 8RM load, 3 s up and 3 s down), a week apart in random order; 20 completed both.
Pain during a single-leg decline squat (SLDS) fell by 0.9 points on a 0-10 scale immediately after exercise (95% CI 0.1 to 1.7), with no difference between the two exercises (interaction p = 0.561), and was no longer significantly below baseline 45 min later (−0.4 points, p = 0.089).
Only 4 of 20 had a clinically meaningful (≥2 point) fall after isometrics and 6 after dynamic exercise; at 45 min, 0 vs 4. Pressure pain thresholds rose briefly at the shin muscle (tibialis anterior), not at the tendon, and tendon thickness did not change.
The authors conclude that contraction mode may not be the most important factor and that patients should not be told to expect complete pain relief from either exercise. This is the base's strongest single test of isometric analgesia, and it did not reproduce the 7.0-to-0.17 result of Rio 2015.
Protocol
Participants: 21 randomised (10 isometric first, 11 dynamic first), 20 analysed (one lost for family reasons). Age 26.5 ± 6.4 years, 41% women, VISA-P 47.9 ± 11.6, median symptom duration 24 months (IQR 10-84), 52% bilateral, worst pain in the past week 7.9 ± 1.6.
Diagnosis: pain at the inferior pole of the patella on palpation and with jumping and landing, pain on the SLDS, plus ultrasound features; worst pain in the last week at least 3/10; no other knee pathology, previous knee surgery or corticosteroid injection in 6 months.
Isometric session (overcoming): seated in an isokinetic dynamometer (Biodex), knee at 60 degrees of flexion, pushing against the fixed lever at 70% of MVIC with the torque verified by the dynamometer; 5 × 45-s holds with 2 min between. MVIC was the peak of three maximal efforts at the same angle, tested the same day.
Dynamic session: leg-extension machine, 8RM load, 3 s concentric and 3 s eccentric through 90 degrees of range, metronome-paced, 3 sets of 8 with 2 min rest. Our calculation: about 225 s under load in the isometric session against 144 s in the dynamic one, so the isometric dose was larger.
Timing: each participant did both sessions one week apart at the same time of day; outcomes before, immediately after and 45 min after exercise.
Outcomes: primary — pain on the SLDS (decline board about 25 degrees, squat to 60 degrees, mean of three, most painful leg); secondary — pressure pain thresholds at the painful tendon, the other tendon, tibialis anterior and the opposite forearm extensor; patellar tendon thickness on ultrasound.
Analysis: two-way repeated-measures ANOVA (exercise × time), responder analysis at a 2-point change with McNemar's test; order and carry-over effects checked and not found.
Key Results
| Outcome (n = 20) | Isometric | Dynamic | Statistics (full text) |
|---|---|---|---|
| SLDS pain, baseline, mean (95% CI) | 5.0 (4.1 to 5.8) | 4.3 (3.4 to 5.2) | — |
| SLDS pain, immediately after | 4.2 (3.0 to 5.5) | 3.2 (2.0 to 4.4) | difference in change −0.3 (−1.3 to 0.7) as printed |
| SLDS pain, 45 min after | 4.8 (3.7 to 5.9) | 3.6 (2.5 to 4.7) | — |
| Exercise × time interaction | — | — | F(2,38) = 0.6, p = 0.561, partial η² = 0.03 |
| Pain, immediately after vs baseline (both exercises) | −0.9 (−1.7 to −0.1) | (pooled) | p = 0.028 |
| Pain, 45 min after vs baseline (both exercises) | −0.4 (−0.8 to 0.1) | (pooled) | p = 0.089 |
| Responders, ≥2-point fall, immediately after | 4 of 20 | 6 of 20 | p = 0.73 |
| Responders, ≥2-point fall, at 45 min | 0 of 20 | 4 of 20 | p = 0.16 |
| Pressure pain threshold, tibialis anterior | +34 kPa (9.5 to 58.5) immediately after, both exercises | p = 0.009; at 45 min p = 0.238; no exercise interaction (p = 0.62) | |
| Pressure pain threshold, painful patellar tendon | no time effect | no time effect | p = 0.239 |
| Patellar tendon thickness | no change | no change | p = 0.593 |
Sign of the between-exercise difference: from the group means the isometric session lowered pain by 0.8 and the dynamic one by 1.1, so isometric minus dynamic is +0.3 (slightly less relief after isometrics); the manuscript table prints −0.3, Clifford 2020 (REF-1149) prints +0.3. Our arithmetic. Either way the interval spans zero.
Against Rio 2015: there, pain fell 6.8 of 10 after isometrics and 2.6 after isotonics in 6 men (REF-627); here 0.8 and 1.1 in 20 men and women with the same exercise protocol at 70% MVIC.
Mechanisms
Measured: a short-lived rise in pressure pain threshold at the tibialis anterior after both exercises (exercise-induced hypoalgesia), but none at the painful tendon, the other tendon or the forearm; no change in tendon thickness.
Authors' interpretation: exercise-induced hypoalgesia is thought to be systemic, so its absence at the tendon and forearm may reflect impaired pain inhibition in long-standing tendinopathy; they call this speculative because there was no pain-free control group.
Authors' interpretation: the much larger effect in Rio 2015 came from 6 male volleyball players and may not generalise; Pearson 2018 (1.7 cm on a visual scale) found a size close to this trial's.
Inference: the isometric session carried more time under load (about 225 vs 144 s) and still gave no more relief, so a dose shortfall does not explain the null result.
Practical Application
Do heavy isometric holds kill patellar tendon pain? In a pre-registered crossover of 21 patients, 5 × 45 s at 70% MVIC cut pain by under 1 of 10, no more than leg extensions, and it faded within 45 min.
Expect small, variable relief, not a pain switch; do not promise relief: 4 of 20 had a meaningful drop after isometrics, none still had it 45 min later. The authors advise that patients should not be told to expect complete pain reduction from resistance exercise.
Choose by preference: because neither contraction type was superior acutely, the authors suggest patient preference can guide the choice. Not from this paper; the base's own practice: whichever is chosen, it is tendon loading inside a progressive programme (REF-626, REF-624), with sport governed by the pain-monitoring rule in SYNTH-73.
Limitations
No no-exercise condition, so the small pain fall could partly be repeated testing; the authors note this does not affect the comparison between exercises.
The outcome assessor was not blinded to the exercise; participants were blinded only to the hypothesis.
MVIC and 8RM were tested on the same day as the sessions; pain during exercise was not collected (a protocol deviation decided after piloting); the affective side of pain was not measured.
Single sessions only; adults aged 18-40 with long-standing pain (median 24 months, 52% bilateral). Results may differ in acute or adolescent tendon pain.
70% MVIC rather than the 80% used in Rio 2017 (REF-1145).
Funding: one author is part of the Center for Neuroplasticity and Pain, supported by the Danish National Research Foundation (DNRF121). The authors declare no conflicts of interest.
How this entry was checked and changed
Why this level
controlled crossover with 21 randomised and 20 analysed (rubric: crossover with ≥15), sized a priori (90% power for a 2-point difference) and diagnosis confirmed on ultrasound; the assessor was not blinded and there was no no-exercise condition; read from the accepted manuscript (full text)
Full text (checked 2026-10-16)
Pre-registered on clinicaltrials.gov (NCT03528746); sample size for a 2±3 point difference with a power of 0.9, requiring 21 participants (full text).
Isometric: 70% of the MVIC sustained for 45s at 60° knee flexion, one 45s repetition a set, repeated five times with two minutes break (full text).
Dynamic: 8RM load, three seconds concentric, 0s isometric and three seconds eccentric through 90 degrees ROM, three sets of eight repetitions, two minutes break (full text).
Interaction F(2,38)=0.6, p=0.561, partial η2 = 0.03; pain lower immediately post exercise by 0.9 NRS points 95%CI 0.1 to 1.7, p=0.028 (full text).
45 min post exercise vs baseline: mean difference 0.4 NRS points 95%CI -0.1 to 0.8, p= 0.089 (full text).
Responders: 4 versus 6 immediately (p = 0.73), 0 versus 4 at 45 min (p=0.16) (full text).
Tibialis anterior PPT mean difference 34 kPa 95%CI 9.5 to 58.5, p=0.009; 45 min 17.2 kPa, p=0.238 (full text).
Table: isometric 5, 4.2, 4.8; isotonic 4.3, 3.2, 3.6; difference -0.3 (-1.3 to 0.7) (full text).
Baseline: age 26.5 (6.4), 41% female, VISA-P 47.9 (11.6), symptom duration 24 (10 -84) months, bilateral 52%, weekly sport 8.8 (4.2) h (full text).
Funding: TGN is part of CNAP supported by the Danish National Research Foundation (DNRF121); "The authors have no conflicts of interest to declare" (full text).