Coaches often look for the slowest lap in a race. But the bigger problem usually isn’t a slow lap. It’s one weak swim wall phase buried inside an otherwise solid swim.

Female swimmer racing with AIM Systems analysis in use

A wall phase includes the turn, the push-off, and the transition back into full stroke. When one of these breaks down, it doesn’t just cost time on that wall. It changes the swimmer’s rhythm for the rest of the race.

Research from the Norwegian School of Sport Sciences (Gonjo & Olstad, 2021) makes this point clearly. The study compared elite and sub-elite 100m breaststrokers using detailed velocity data. Elite swimmers were faster mainly due to clean-swimming velocity and glide velocity off the wall, not a faster pull-out. In fact, there was no measurable difference between elite and sub-elite swimmers in the pull-out phase itself.

That finding matters because it shows the pull-out and transition are an under-coached area, even among strong racers. The researchers modeled what would happen if a swimmer’s own best pull-out and transition segments replaced their weaker ones. Two swimmers with nearly identical overall times could both have gone under 60 seconds. The gain wasn’t from training harder. It came from consistency at the wall.

Why one bad wall phase spreads through the race

A slow push-off forces a swimmer to accelerate harder to catch back up to race pace. That extra effort raises stroke rate and fatigue earlier than planned. As a result, the next lap often suffers too, even if the turn on that lap was technically fine.

This is why dropoff, the change in lap time compared to the previous lap, is such a useful number to track. A spike in dropoff right after a wall usually points to a transition problem, not a swimming problem.

Finding the weak wall with real data

Most coaches catch an obviously bad turn by eye. What’s harder to catch is a wall phase that looks fine but is quietly a second slower in push-off timing or breakout distance than the swimmer’s other turns.

This is where AIM Systems earns its keep. Because the system tracks turn time, breakout time and distance, and lap-by-lap dropoff automatically, it flags the one wall that’s dragging on the race. It isn’t guesswork from watching a replay. It’s a spreadsheet showing exactly which turn cost the most time, lap by lap.

A coach can then compare that swimmer’s weak wall against their own best turn from a prior race. That’s the same logic behind the pull-out findings above: most swimmers already have a good wall phase somewhere in their history. The job is making it the norm, not the exception.

  • Pull up turn time and breakout distance for every wall in the race.
  • Find the one wall with the worst numbers relative to the swimmer’s own average.
  • Compare it against that same swimmer’s best recorded turn for the stroke.
  • Build the next few practices around closing just that one gap.

Because AIM Systems is a fixed, markerless camera installation, this data comes from every race the swimmer does at the facility. No sensors, no manual timing, no guesswork about which wall was actually the problem.

If you want to see how this looks with your own swimmers’ data, get in touch with AIM Systems. No pressure, just a look at what’s possible.

Frequently asked questions

Why does one weak wall phase affect the whole race?
A slow push-off forces a swimmer to work harder to recover pace, which raises fatigue and often slows the following lap too.

What should coaches track to find a weak wall phase?
Turn time, breakout distance, and lap-by-lap dropoff together usually reveal exactly which wall is costing the most time.

Does a faster pull-out actually separate elite swimmers from sub-elite swimmers?
Research using the AIM race analysis system found no measurable pull-out speed difference between elite and sub-elite breaststrokers, meaning other phases mattered more.

Sources

  • Gonjo, T., & Olstad, B.H. (2021). Differences between elite and sub-elite swimmers in a 100 m breaststroke: a new race analysis approach with time-series velocity data. Sports Biomechanics. https://doi.org/10.1080/14763141.2021.1954238