Do I need to be out of breath after exercising for it to be doing any good?

[FakaP]

I have recently taken up swimming regularly again in a bid to loose weight and get fit. Swimming is ideal for me, I enjoy it, and I have dodgy knee joints so high impact exercise Is out anyway.

I used to swim a lot when I was younger, and have a good technique, therefore it is not difficult for me to swim 50+ lengths in a session. I don't feel physically tired after 50 lengths, and I am not out of breath. Does this mean it is not actually doing me any good?

What with work and home life I don't have an awful lot of time spare, so just swimming for longer is not really an option.

Any ideas? Should I find something else that leaves me feeling like I am pushing myself physically or is just doing the exercise enough?

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how about just swimming a bit faster, more lengths but in the same amount of time.
IME good swimmers can swim with very little effort so it would prob help if you pushed yourself a bit more

Do you vary your stroke?
I could swim breaststroke for miles but 10 lengths of face paced front crawl and I'm gasping!
Have you tried the Swimfit programme? They offer a variety of training schedules.

How long does 50 lengths take you? IMO if you are a reasonable swimmer, 50 lengths (of a 25 metre pool?) is not a lot.

Can you do some sprints and timed stuff? So warm up for a few lengths, but then do different amounts of fast-as-you-can training with short recoveries.

So something like:
Warm up 8 lengths / 200m
5 x 2 lengths / 50m as fast as you can with 10 seconds recovery between each set
3 x 4 lengths / 100m as fast as you can with 15 seconds recovery between sets
1 x 8 lengths / 200m as fast as you can, then 30 seconds recovery after
3 x 2 lengths / 50m as fast as you can, with 10 seconds recovery in-between
Cool down 6 lengths easy

That's still 50 lengths. And total non-swimming time is small. But doing different intervals all-out (and check your pacing on the pool clock) should help. You should really need those recovery bits.

Try hypoxic training - you'll soon be out of breath! Basically reduce the amount of breaths you take each length whilst swimming as fast as you can. I aim to breathe no more than twice for 10 x 1 length sprints, with no more than 15 secs rest after each length. A good one to do at the end of a session.

a good swimmer should be able to do 50 length in 25 minutes or less so it's a pretty short session really

The answer to your initial question however is yes. Any swimming will be doing you 'good'.
However if you want to get fitter and lose weight you will need to push yourself. Agree with Pootle.
You said it yourself, you're not tired or out of breath ..... I'm newer to swimming ( won't have your technique ) after an hour's session ( 1800m or so of drills and intervals ) I'm pretty beat up!