Overspeed towing flatters the stopwatch and teaches very little

Being pulled beyond your own top speed changes the mechanics of running in ways you cannot use unassisted.

Attach a sprinter to a bungee, pull them through a timing gate, and everybody goes home delighted. They just ran quicker than they ever have. The problem is what they were doing while they did it.

The theory is that the nervous system needs to experience a higher leg speed in order to learn to produce one, and there is something in that. Coordination at velocity does seem to be partly a learned skill and you cannot practise something you have never done. Fine. But the assisted run is not the same movement. The pull applies a horizontal force at the waist that the athlete did not generate, which means every ground contact is now happening under conditions the athlete cannot recreate. Contact times shorten because the body is being dragged off the foot. Step length grows for a reason that has nothing to do with pushing harder.

So what does the athlete rehearse? A rhythm they cannot produce, with a force profile they never generate, at a body position the tow rope is holding for them. Then you unhook them and ask for a transfer that the mechanics do not support.

There is also a load question that nobody likes discussing. Higher leg velocities mean more demand on the hamstring during late swing, at exactly the moment the muscle is most vulnerable, and the athlete is being pushed past a speed their tissue has organised itself around. If somebody handed me a protocol guaranteed to tear a hamstring in April, it would look a lot like heavy overspeed work in March.

I would rather chase the same adaptation the slow way. Short flying runs on a good surface, fully recovered, with enough rest between them that every rep is genuinely maximal. It is less exciting and the numbers on the watch are smaller. The mechanics are the athlete's own, which means the improvements survive the removal of the equipment.

A very slight downhill, one or two degrees, is the version of assistance I will accept, because gravity applies its help through the same route the athlete's own force travels.

Bungees make for a good video. That is mostly what they are for.