I've been swimming lengths for about a year and usually swim 2000 metres during workouts. I structure my swims into different intervals and they are long distances, fast pace and sprints. What I find is during these fast pace lengths(100m), my swimming technique falls apart in the final 35-40 metres. How can I keep my stroke more consistent and stop my stroke from falling apart? Any help would by greatly appreciated.
Practice, practice and more practice.
Generally your form will fall apart in almost any sport once you start getting fatigued. If it happens every time on your fast 100's, then you are going too fast for your fitness. If you have been swimming for a year and showing very little improvement in your overall times, then you may have some stroke flaws that need work.
Stroke flaws may also play a part in the breakdown, if you are having to fight your stroke, that will fatigue you faster than swimming with good form.
Swimming is a sport that is almost entirely form based, so the better your form the faster you will go for the same effort. This is due to more efficiency in the water, less drag, better breathing and reduced fatigue.
My dividing line is around 2:00/100m. Assuming that fitness itself is not a limiter, if you can go 2:00/100m or faster for a 400m or longer swim, then more hard work is probably what you need to get faster. If you are slower than 2:00/100m for that distance, then you probably have some form problems that needs attention. Obviously in the middle, you could have a little bit of both.
Just as an N=1 sample, I was a competitive swimmer for many years, and I have not been in a pool for a workout in close to 3 years. I can still get in a pool and be able to do 100m in under 1:30, under 1:15 if I really push it. That's all from form.
My suggestion is to pick up a copy of the book Total Immersion, it specializes in teaching about good form with some interesting concepts thrown in. One thing I think I recall reading from it is that when you feel your form falter during a rep, stop! Or the bad form becomes habitual. Swim only when the form is good, and build up distance and speed at the same time as long as form remains good.
Swimming only when form is good makes a habit out of good form and trains your body to remain consistent in good form even if you get tired and have a hard time keeping good form.
Go slow at first while you work on form. The surest sign of weak form is if you can't do it correctly when you go slow. It's like a balancing act, unlike when you go fast and bad form doesn't throw you off balance as easily.
After that, you can do some High Interval Intensity Training (HIIT) from time to time and for only as long as form stays good, with 80-100% effort. That will boost your endurance for short distance sprints and you'll eventually increase the distance you can sprint using good form.
One tool that can help you to control the frequency of your strokes is a tempo trainer.
Controlling the frequency would let you to gradually increase it until you reach a point where you feel that the technique fails.
E.g swim 50m with a time between strokes of 1:25. If you that the technique is ok, decrease it to 1:15, swim 50m, etc
Once you find a frequency that works for a short distance, increase the distance for the interval.