Question about increasing cardio endurance

Ms_J1

So... all my life I've been told or heard that in order to improve your cardio endurance, you have to raise your heart rate to at least 75% of your max heart rate for 20 minutes straight, 5 days a week and that if you let your heart rate go below the 75%, even for a moment during that 20 minutes, you're wasting your time.

What I don't understand is that if this were true, then why do "they" tell people who are seriously out of shape and starting a cardio routine for the first time to "work up to 20 minutes" by starting at 5 minutes and slowly increasing the time each day until you reach 20 minutes? How can you work up to 20 minutes if 20 minutes is the minimum amount of time you need to improve cardio endurance?

Is there no benefit in doing 3 or 4 sets of 10-minute cardio exercises every day? I would think that since the heart is a muscle just like any other muscle, it can be strengthened and built upon just like any other muscle. What am I misunderstanding?

MeanderingMammal

.... if you let your heart rate go below the 75%, even for a moment during that 20 minutes, you're wasting your time.

That bit is nonsense, but the general principle is that you can improve your CV performance through doing different types of CV activity. Endurance and capacity are both improved by doing appropriate training.

In principle your CV system operates at a working level of HR, it has a maximum rate and there are different ways of estimating that. Note that the most common estimation (220-age) is very crude and inaccurate for many. Within the range between your working heart rate and maximum there are a couple of thresholds where the type of performance changes.

Increasing your HR to a higher level for a sustained period of time will improve endurance, or your ability to operate at a higher HR for a sustained period. That's essentially where the 75% threshold comes in, it's a rate that a healthy heart can sustain for a long period of time. As you approach 80-85% the effects on the wider system change and waste products start to build up, which will eventually reach a level where they'll impair performance.

There is no magic switch that kicks in at 20 minutes, the performance improvement will happen as long as the CV system is placed under stress.

What I don't understand is that if this were true, then why do "they" tell people who are seriously out of shape and starting a cardio routine for the first time to "work up to 20 minutes" by starting at 5 minutes and slowly increasing the time each day until you reach 20 minutes? How can you work up to 20 minutes if 20 minutes is the minimum amount of time you need to improve cardio endurance?

If one can't do 20 minutes then there is little point in advocating 20 minutes. By stressing the system and improving it over time then the capacity to sustain elevated HR for 20 minutes is built up.

Is there no benefit in doing 3 or 4 sets of 10-minute cardio exercises every day? I would think that since the heart is a muscle just like any other muscle, it can be strengthened and built upon just like any other muscle. What am I misunderstanding?

If you look at a plan like Couch to 5K, a running coaching system, then it's clear that there is a progression. It starts by having a 60 second run period with a 90 second walk period, repeated 8 times in a session. That then builds over nine weeks, steadily increasing the run periods and reducing the walk breaks until it's a 30 minute continuous run. The CV system becomes trained over time.

Doing 3-4 ten minute sessions will have an effect, but it won't increase endurance unless you're increasing the length of each of those sessions every week.

There is a mode of training called interval training, and another known as tempo training, where the periods of exertion are shorter but the intensity is higher. These have different effects in a trained exerciser, tempo training improving the threshold at which the waste products build up and intervals increasing the capacity of the system to consume oxygen, so increasing potential exertion. So a short session has a place in any trainers portfolio.

To get the best CV improvements the first thing to work on is increasing the length of the session, once a steady state can be maintained for about an hour then there will be benefit from tempo and interval training.

SingingSingleTracker

So... all my life I've been told or heard that in order to improve your cardio endurance, you have to raise your heart rate to at least 75% of your max heart rate for 20 minutes straight, 5 days a week and that if you let your heart rate go below the 75%, even for a moment during that 20 minutes, you're wasting your time.

What I don't understand is that if this were true, then why do "they" tell people who are seriously out of shape and starting a cardio routine for the first time to "work up to 20 minutes" by starting at 5 minutes and slowly increasing the time each day until you reach 20 minutes? How can you work up to 20 minutes if 20 minutes is the minimum amount of time you need to improve cardio endurance?

Is there no benefit in doing 3 or 4 sets of 10-minute cardio exercises every day? I would think that since the heart is a muscle just like any other muscle, it can be strengthened and built upon just like any other muscle. What am I misunderstanding?

Here is a link to what is known as "training zones" for cardio. Each Zone has a physiological adaptation (there is a chart at this link that shows that as well). http://home.trainingpeaks.com/blog/article/power-training-levels

I like to break the 6 main training zones down into a simple perceived effort scale like this:

1. Old lady pace
2. Chatty pace
3. Feel good hard
4. Feel bad hard
5. I am going to die
6. Flat out

It's important to note that cardio training zones are based on what is known as Functional Lactate Threshold Power through a test - and not on heart rate. This is done through a test (various durations of the test are used from 20 minutes, to 30 minutes to 60 minutes, or even a ramped MAP test). So when somebody says "75% of maximum HR" - that's going to be a different percentage than what you see in the link above which is all based on a level you can sustain for 60 minutes (FTP). My average heart rate for my current FTP is about 171-174 which is a bit below whatever my maximum HR must be. I don't fit well into the "formulas" as I am at least one standard deviation from the typical formula to determine maximum HR. I hit 180-184 on a regular basis when doing the very upper zone intervals - or at the end of a MAP test.

If I was mis-informed that any cardio work that I did below 75% of my maximum HR was pointless, it would wipe out my Zone 1 as well as the aerobic base building I do in a good portion of Zone 2 (like the 50 mile ride I did this past Sunday). This is especially an important Zone to build a big aerboic base to improve your duration. I usually spend a lot of time in it every bike season from January - May. And of course, as the body adapts through structured training, what was quite an effort in the early season becomes easy recovery pace later on in the year. So you need to be careful not to listen to that particular advice. The wrench in the calculation that is thrown, is figuring out anyone's actual maximum heart rate. Do you know what your actual maximum HR is so you can figure out your training?

In terms of breaking up your sessions into shorter segements...

Yes, there is benefit to doing 3 or 4 reps of 10 minute cardio sessions per day to get some time in as cardio is cardio and it doesn't have to be constant as you are in the beginning stages of working your way into shape. Ideally, you will want to increase those durations as your system adapts so that you keep stressing your system for growth in building your aerobic base. Be it through 4 x 10 minute sessions, some 3 x 13 sessions, some 2 x 15 sessions, and so on and so forth until you can link together a couple of 2 x 20 sessions and on and on until doing an hour or more is attained.

There are so many formulas to calculate or estimate your maximum HR. Here's a link that allows you to use a lot of formulas by plugging in your information one time....

http://www.brianmac.co.uk/maxhr.htm

If I plug my age into that calculator and choose cycling as my activity - whether or not I choose "average" or "elite" - the numbers for my maximum HR are all lower than I see in a mountain bike race or when I do upper level intervals. It just illustrates that it is not easy to figure out one's maximum heart rate as we don't all fit so neatly into a "formula". You will simply have to estimate yours based on your current level of training to use as a starting reference.

Ms_J1

Awesome information, guys! Thanks!

Now I need to digest all this and figure out the best way to do my cardio routine. I'm a swimmer (after decades of being on hiatus), and although I swim at a moderate pace for about an hour most days, I've been incorporating sprint intervals into my workout. I do 10 intervals (500yd total) without resting and each interval is a 25yd butterfly sprint (one length) + 25yd backstroke kick (one length, moderate pace). I don't stop between each interval to rest simply because I consider the backstroke kick as my "rest" (to keep moving while giving my arms a break at the same time). My problem is that since I've been doing the sprint intervals, I have found that I can't advance my sprint distance to 50yds. Twenty-five yards continues to kill me. Yet, I've also noticed that my heart rate is going down faster on my 25yd back kick than it did a month ago. So, maybe I should be doing 10 sprint intervals in three sets or extend my sprint length to a length and a half and my back kick to a half length. Or maybe I should just step up the back kick to a faster pace.

This was so much easier when I was a kid and had a swim team coach yelling at me all the time from the pool deck to pull faster. I never had to think about any of this because it was all thought out for me by someone else. I miss those days.