By Nicolas Desjardins, PhD in Natural Medicine · DBA(c) · Master’s in Neuroscience (in progress), designer of the Q-Technology system. Nicolas Desjardins is not a medical doctor. October 2026.
Lire cet article en français : Ta puissance plafonne ? Ton capteur voit la sortie, pas l’asymétrie.
The short answer. To increase power, you almost always track one overall number: jump height, your 20-meter time, bar speed. That number doesn’t say how your two sides and your trunk shared the work. Research is more nuanced than people think: in a meta-analysis of adult athletes, asymmetry between the legs had no measurable link with two-leg jumping and only a weak link with sprinting and change of direction (Fox et al., 2023). Our hypothesis: a body organized around compensation loses part of the force it produces before it reaches the ground or the bar. During the Test Posture Parfaite, we look at your strength and stability tests on the right and the left, and at your postural tilts, with no equipment.
Power isn’t a number. It’s a transfer.
A jump, a sprint, a snatch, a strike: force starts in the legs, travels through the pelvis and the trunk, and comes out through the ground, the bar or the fist. Your sensor sees the output: a height, a time, a bar speed. It doesn’t tell you whether one side pushed harder than the other, or whether your trunk passed the force on or absorbed part of it along the way.
The day the number plateaus, you don’t know where to look.
What the studies really say about asymmetry and power DOCUMENTED
We’d all like a simple rule, like “10% asymmetry means 10% less power.” The studies don’t give one.
- The meta-analysis in adults. Fox, Pearson and Hicks (2023) pooled 11 studies of adult athletes, with asymmetry measured through single-leg jumps. With two-leg jump performance, no measurable link (r = 0.05). With sprinting (r = 0.20) and change of direction (r = 0.24), a weak link: more asymmetry went with slightly slower times. For the authors, asymmetry seems to weigh mainly on tasks where each leg works alone.
- Each leg’s power, measured on force plates. In 167 NCAA Division I athletes, Bell et al. (2014) measured the force and power of each leg during a countermovement jump. Above 10% power asymmetry, jump height tended to drop, with a large effect size, but in only 9 athletes, and the difference was not statistically confirmed. Lean mass asymmetry in the pelvis and legs explained only about a quarter of the power asymmetry: a large share remained unexplained.
- A finding that adds nuance. In 30 male team-sport athletes, Lockie et al. (2014) found no difference in speed (20 m, 505, T-test) between the more and the less asymmetrical athletes, with asymmetries of about 10% in the vertical jump, 3% in the broad jump and 5% in the lateral jump. What mattered was each leg’s performance, especially in horizontal and lateral jumps.
What they don’t show: these studies are all associative. None shows that reducing an asymmetry increases power, and none sets a threshold that holds for everyone. What they do show: asymmetry depends on the task. On weak-side strength, see also your 1RM can’t see your weak side.
The leak: our reading HYPOTHESIS
Here is our reading, and it is a hypothesis: power requires both sides and the trunk to transmit force together. When one side gives way earlier, the body doesn’t stop, it compensates. The strong side takes more than its share, the pelvis shifts, the trunk locks up to stabilize rather than transmit. The movement counts, the number comes out, but part of the force produced never reaches it.
Bell’s study leaves a question open: if lean mass explains only about a quarter of power asymmetry, the rest comes from somewhere else. The authors point to other possible factors, which they did not measure: neuromuscular control, strength, muscle cross-sectional area, joint coordination. Our hypothesis is that part of it lies in organization; it remains to be shown.
You’re not stuck. You’re compensating.
What you can do at your next session, without buying anything: add single-leg jumps, vertical and horizontal, compare both sides, and repeat them a few weeks apart. In Lockie’s study, it was each leg’s performance that went with speed, not the gap between them.
What machines measured at R15 Studio
R15 Studio (Paris) posted figures on its social media, measured on machines during sessions with our circuits. R15 Studio session, the studio’s figures: on the trap bar deadlift, +10.8%, +10.8% and +17.1%; on the isometric deadlift, +28% measured on the ARX and +24% on the Kinvent. One athlete, whose personal record on the ARX was 230 kg, added 46 kg with the Q-Pro, or +20% over his record (R15 Studio session, the studio’s figures): this is an individual, uncontrolled case. The studio is due to send us the average of 12 athletes measured on the ARX: it will be added here as soon as we receive it, with its source.
Read these figures for what they are: figures published by the studio, measured on machines during sessions at R15 and not during the Test Posture Parfaite, on observed, uncontrolled cases, with no control group and no blinding. These figures don’t demonstrate our leak hypothesis, and we promise you no gain in load. What the test shows you is something else: your strength tests and your posture, before and while wearing the circuit.
Passive · Non-invasive · No battery · No electrode | Functional observations from internal tests | Individual results vary | Not a medical claim.
What we look at during the test, and what we’ve observed
What we look at, before and while you wear the circuit, during the Test Posture Parfaite (fifteen minutes, with a certified tester, no equipment):
- strength and stability tests, right and left, holding or giving way;
- the tilts of the pelvis and shoulders on three planes, in centimeters;
- neck rotation, scored out of 7 on each side.
The test measures neither your jump height, nor your sprint, nor your maximum load, and uses no device. If it shows nothing, it is refunded.
What we observe OBSERVATION: while the circuit is worn, strength tests that gave way on one side now hold, and posture reorganizes on three planes (see what we call perfect posture).
Functional assessment, non-medical · Before/after protocol · Observations from internal tests · Individual results vary · Not a medical claim.
Our hypothesis HYPOTHESIS: the passive resonant circuit removes nothing and blocks nothing. It gives the nervous system a coherent, stable reference. This is a hypothesis about the mechanism, and it may be wrong.
Support, not cure. While you wear the circuit, the effect is there. Take it off, and you’re back where you started, like glasses: you wear them, you see; you take them off, you don’t. The circuit replaces neither your power program nor your unilateral work.
FAQ
How do I increase my power?
Through training first: strength, speed, plyometrics, technique. Add single-leg jumps, compared right and left: in team-sport athletes, each leg’s performance was linked to speed (Lockie et al., 2014).
Does asymmetry lower jumping or sprinting?
Not in a simple way. In adult athletes, it had no measurable link with two-leg jumping and a weak link with sprinting and change of direction (Fox et al., 2023). All these studies are associative: they show links, not causes.
What level of power asymmetry is normal?
In 167 college athletes, 95% fell between about -10% and +11.5% power asymmetry in the jump, and only 3 of 167 (about 2%) exceeded 15% (Bell et al., 2014). These are benchmarks for that population, not a universal threshold.
Do the R15 Studio figures prove the circuit increases power?
No. They are figures published by the studio, measured on machines during sessions at R15, uncontrolled. They show what was observed in those cases.
Does the test measure my power with a device?
No. The test is done with no equipment: strength and stability tests on the right and the left, postural tilts on three planes. Fifteen minutes, €33, with a certified tester, refunded if it shows nothing. Functional assessment, non-medical · Individual results vary.
Can I wear the circuit in competition?
Passive circuit: no substance. Check with your federation.
Your sensor sees the output. Come and see where your force goes: book your Test Posture Parfaite, refunded if it shows nothing.
Sources
- Fox KT, Pearson LT, Hicks KM. The effect of lower inter-limb asymmetries on athletic performance: A systematic review and meta-analysis. PLoS One. 2023;18(6):e0286942. https://doi.org/10.1371/journal.pone.0286942
- Bell DR, Sanfilippo JL, Binkley N, Heiderscheit BC. Lean mass asymmetry influences force and power asymmetry during jumping in collegiate athletes. J Strength Cond Res. 2014;28(4):884-891. https://doi.org/10.1519/JSC.0000000000000367
- Lockie RG, et al. Relationship between unilateral jumping ability and asymmetry on multidirectional speed in team-sport athletes. J Strength Cond Res. 2014;28(12):3557-3566. https://doi.org/10.1519/JSC.0000000000000588
