Where the targets come from
Research guided this.
The judgement was ours.
There is very little published measurement of a racing start, and almost none of it uses the same body landmarks this app does. The papers below shaped what SwimVolt measures. The ranges you are held to are mostly coaching judgement — 1 of 27 comes straight from a study.
Set by coaching
Set by coaches and biomechanists, and by swimming the event. Judgement, not measurement.
- Back knee angle
- Head–shoulder line
- Shoulder–hip line
- Back foot angle
- Hips above shoulders
- Back heel
- Weight forward
- Not falling
- Arm pull
- Push finish
- Toes pointed
- Hands-first entry
- Hands before head
- Hands together
- Feet together
- Hands-in angle
- Feet-in angle
- Pike or arch
- Head vs arm line
- Arms straight
Our own estimate
No published measurement matches how this app measures these, so we picked the range.
- Takeoff angle
- Block time
- Entry angle
- Front knee angle
- Head/gaze angle
- Back leg bend
Taken from a published study
Lifted straight from a paper, measured between the same landmarks this app uses.
- Forward lean
The papers
What each one contributed.
- The effect of body position and mass centre velocity at toe off on the start performance of elite swimmers2021
Shepherd I, Lindley MR, Logan O, Mears AC, Pain MTG, King M · Sports Biomechanics · 24 elite swimmers (12 men, 12 women)
Which parts of a start actually predict a fast time — trunk position matters, individual limb angles at takeoff do not.
- Key Parameters Affecting Kick Start Performance in Competitive Swimming2021
Matúš I, Ružbarský P, Vadašová B · Int. Journal of Environmental Research and Public Health 18(22):11909 · 18 male competitive swimmers, 50 m freestyle 23.3 s
Set-position knee angles and entry angle in competitive swimmers. Our front-knee range started here at 125-140°; the ceiling is now 160°, raised by coaching after every reference swimmer measured above it.
- Changes in the front and rear knee angles depending on the body and kick plate positions during the kick start2020
Matúš I, Kandráč R, Vadašová B, Čech P, Ružbarský P · Journal of Physical Education and Sport 20(S6) · 10 swimmers across 15 block configurations, 45 starts each
The only study here that changed swimmers' set-up and timed the result, rather than measuring what swimmers already did. It shaped how we think about back-knee bend; the range we hold you to is the coaching table's, not this paper's.
- Predicting dive start performance from kinematic variables at water entry in (sub-)elite swimmers2020
van Dijk MP, Beek PJ, van Soest AJK · PLoS ONE 15(10):e0241345 · 14 sub-elite and elite swimmers, 349 starts
Entry angle across 349 starts, corroborating the range above independently. The band we use is now the coaching one and slightly shallower at 30-40°.
- The effect of knee angle on force production, in swimming starts, using the OSB11 Block2012
Slawson SE, Chakravorti N, Conway PP, Cossor J, West AA · Procedia Engineering 34:801–806 · 10 national-level sprint swimmers on a force-instrumented block
Set-position knee angles in the fastest starts, measured against actual force production.
- Factors affecting the underwater phase of the swimming start2017
Tor E · PhD thesis, Victoria University · 14 elite swimmers on an instrumented OSB11 block
Where block time and entry distance sit for elite swimmers, and the distinction between the angle of your body and the angle you are actually travelling — which is why this app measures both.
- Engineering Elite Swimming Start Performance: Key Kinetic and Kinematic Variables with Reference Values2026
Born D-P, Nussbaumer L, Buck M, Ruiz-Navarro JJ, Romann M · Bioengineering 13(2):180 · 136 national-team swimmers, including Olympic medallists and a world-record holder
The take-off speed comparison range. Not a target — even its slowest swimmers are national-team level, so it shows where a number sits rather than grading it.
How much to trust the measurements
We filmed 12 dives with two phones at once. Some measurements agreed every time. Others changed their verdict on where the camera stood.
Agreed every time
- Block time
- Hands-on-block time
- Take-off speed
Worth following across a season.
Changed with the camera
- Front knee angle80%
- Head/gaze angle67%
- Takeoff angle60%
- Forward lean45%
Read these within one clip, not across sessions.
One swimmer, one pool, one evening. Enough to know which measurements not to lean on, not enough to claim an accuracy figure.