Benefits of long swims (and run/bike)? (Page 2)

1st things 1st - training levels are man made to help train more efficiently by maximizing the gains of certain training adaptations. Still all training adaptations interlayer with each other hence even when doing a session at threshold power/pace you are not only inducing that adaptations but also others like muscle fiber fatigue resistance which usually gains are maximized when training around 70-75% of power threshold/pace. The same happens when you are doing a long steady state run/ride, you are maximizing training adaptations like muscle fiber fatigue resistance but also you are increasing your lactate threshold to some degree.

With that out of the way your main goals when training should be: 1) do more training load (just swim/bike/run) and 2) do specific training, which is the more specific training adaptations relevant to your main event the better you'll be prepared for it.

The reason why athletes hit plateaus is because their training load gets stuck in a certain range - it doesn't matter if you vary your intensity and duration, if you always do the same amount of training load your body eventually will adapt and gains will be diminished or stopped. In order to do more training you need to play with the equations (load = volume/duration + intensity), hence if you only can train 10 hrs x week you'll have to do some of that training more intense. But it will reach a point in which training at higher intensities will be incrementally more difficult and still you will plateau at some point. OTOH instead of sticking to only training 10 hrs per week you decrease your intensity so you can handle more training hours and now train 12- 14 hrs your body will now have to adapt to the new load and most certainly fitness gains will proceed.

In your case the reason you improved by running more is because your total load was higher of what you were used to regardless of the load mix. In order to accommodate more training you had to slow down a bit to do more. Also if your goals are to race long distance events then the more specific training you get to do the better.

In terms of biking and swimming, yes it works the same way. In fact it is good IMO to add some big/long sessions in the mix regardless of your goals. If you usually swim 4x 2000k per week, if every other week you make one of your sessions a 4-5k you will increase your load by exposing your body to new training adaptations and improvements in fitness will follow. The same applies for the bike.