Swim Training : Time Vs Distance, base interval or rest interval, what's best??

I often see many athletes especially beginners and at older age struggling with swim training. A lot has to do with technique and proper way to incorporate technique (based on individual needs and not doing what swimmers do) but I also see a wrong approach to training, not focusing on proper physiological adaptation.

Swim has for many years used a traditional way of training based in distance for example, 2,000m or yds and base interval, meaning if you do 20 x 100m/yds leaving at 1:30 min./100 you have to swim faster then 1:30 and rest whatever time you have left. These have worked well for a lot of athletes once you know their level but for the majority of athletes out there, I see coaches and athletes trying to guess what they can swim (speed/time) to build a proper session based in distance and interval. And if we take in consideration different fatigue level of the athlete, this system can be even further off to the original designed goal.

For example, if the goal of the session is to build endurance, then we would be looking to swim at an aerobic pace with short rest intervals. So if we have two different athletes swimming the session at the example above, 20 x 100m/yds at 1:30 base interval, we can have the athletes doing different things ! If one is fitter then the other and can swim aerobically 100m/yds in 1:10, then 1:30 interval would give him too much rest for full endurance benefit. Ideal would be then to adjust it to 1:20 but then you would need to keep changing sets based on the fitness of the athlete and guessing their fatigue level. Now if the other athlete is the opposite and struggles to make the interval and swims 1:25, he would NOT be swimming aerobically and would probably not be able to finish the set as the 5s rest for a "Grey Zone" intensity swim will fatigue him quickly.

What I have been doing with my athletes for years is to design sets based on rest intervals instead so knowing we have an endurance set for example, I give them 10s rest and ask for easy effort. This way I prevent athletes from resting too long or resting too little and performing the session at the wrong intensity. Also how many of you have gone to the pool and it's feeling "off" or tired? Not only for physiological but also mental reasons, the rest intervals works best because you will not be frustrated for not swimming at the specific base interval and will keep proper intensity and goal of the session, helping recovery and staying mentally positive for next day's session. 

We all know that our body only know two things: "Time and Effort". It means that all the body knows is how long you have been exercising and how hard. Body does not know how far you have swam in distance. So my questions is then WHY should we try to guess a distance we can swim at the different effort levels to design a swim set?

Recently I have created a new adaptation method I call WCF - "Whichever Comes First, time or distance" This way I can progress athletes based on time so the distance they achieve will depend on their fitness level and progression. I can design sessions I call their "Goal Distance Session" but they will only swim the time I describe for the day. So novice or athletes getting back in shape will swim 25 to 30 min. sessions until we feel he/she is fully adapted, only then we progress. By prescribing proper adaptation, I can also improve their recover and quality of the sessions. I see too many athletes logging miles too soon and only getting fatigued and executing the quality sessions SLOW !

When planning your swim sessions, do not worry about the distance, but time instead as it's a better measurable progression/adaptation you CAN actually control, independently of your level of fitness or fatigue on the day.

Train smarter and achieve your goals quicker :)