Why you wouldn't mix cardio and strenght training

2dayirun4me

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smlamb33

This sounds like great info! Thanks so much for sharing! We can all always use more info. to get fit!
I just started alternating cardio and strength training a few weeks ago. Strength training 3x a week and cardio the other 4 days. Although, the cardio on Saturday and Sunday are lighter cardio days like walking.
Thanks again for the tips!!

valerieschram

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jg627

It even applies to really overweight people, though maybe not to the same extent. I was 300 lbs when I started my weightlifting routine. I was able to do cardio with it for the first couple months or so, but after that forget it. I have to drop the intensity of my strength training for a bit every now and then so I can start doing the cardio again. How intense your strength training regimen is probably plays a big role.

LilRedRooster

There are several factors that play into how people should approach their training, and it's not just a simple "You need to cut out cardio if you want more muscle".

The twitch fibers play a role in how your muscles will respond, but every person is going to have a different ratio of those fibers in their body, and those don't change over time. At all. You have what you were born with, which is why certain people are sprinters, and certain people are distance racers, and rarely do they mix and create superior athletes in both. Distance racers have more aerobic muscle fibers, while sprinters require more aerobic. Some people build more muscle easily, and that's because they have more of one fiber, and they're usually at a more optimal length that creates larger diameters.

But ANY exercise that puts those muscles into overload and fatigue, where the myosin and actin heads cannot connect any longer, will cause muscle growth, in either fiber. Even the cardio exercises send slow twitch fibers into hypertrophy (getting larger), if you overload them to a point where the sarcomeres experience fatigue and need to rest. The main thing is that ONLY doing activities that require certain fibers, like aerobic, tends to send the other fibers into atrophy (where they shrink), because they aren't needed as much. Only after an extended period of time, or if someone has extremely low body fat or poor nutrition, do those fibers actually break down for energy or protein, because the muscle will simply shrink first before actually breaking down.

So saying "If you do cardio and strength training, you're going to catabolize muscle" is up for serious debate, because the only way that you break down any muscle tissue is if you stop overloading it for long periods of time, and you aren't getting sufficient nutrition to supply energy for the muscle repair that creates larger diameters. It's not just going to happen because your body is introduced to another activity for a little while. The human body would not have managed to get through the evolutionary chain if it broke down muscle all the time on a dime, because once broken down, those fibers don't come back. Literally, you cannot grow more muscle fibers once they're gone.The only way to improve muscle function would be to work the surrounding fibers harder and cause them to grow larger, which wouldn't be efficient if you had to do that every time you started a new activity.

The main benefit to doing both cardio and strength training is that every fiber gets used, and overloaded to the point where they need rest. You can do cardio, target one set of muscles, and then do strength training, which targets different fibers. You can do more of one than the other, and experience more growth in one area while doing so. The thing that is detrimental to seeing more muscle growth is not allowing enough time for rest. That's all. You're not going to experience degradation of muscle if you allow for rest and have proper nutrition to maintain that exercise. The only thing that might happen is that hypertrophy would probably be slower in general. But cross-training will keep your muscles more fit, because they're consistently exposed to new stresses.

mfpcopine

I don't mix them for the simple reason that it's hard to do both well at the same time and there's a risk of injury. You don't even have to be using a heavy weight. The writer Nora Ephron wrote about swinging her little 2-pound weights for 45 minutes (I don't remember all the details, but she overdid it). Her shoulders were screwed up for two months.

Despite what the Pilates and Yoga people say, strength training requires focus and serious exercisers are acutely aware of their form and breathing.



Strength training, with your full strength, followed by cardio is the best way to do it.

lisao62

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mfpcopine

Raz,

This was very interesting and informative. I'm hoping this question isn't stupid. On the days I weight train, I typically do about 10 minutes of cardio before hand just to warm-up. Should I not be doing this and if not, is there something else I should do to warm-up or just hit the weights?

you can do a few warmup sets...

I've always read that a little light cardio was fine to warm up. Warm up sets are good, too.

scottb81

If there is roughly total 2000cals of glycogen stores in my muscles + liver, presuming I do eat carbs to replenish these and am not in a ridiculously low deficit, why then can we not do say, for example, a 300cal strength session followed by a 400cal cardio session? are there still 1300cals of glycogen sitting in the muscles ready to be used for repair + general movement?

If you eat properly, you will replace all your glycogen stores within 24 hours, even after a very hard exercise session.

If you do not eat properly then you will gradually deplete them until there is nothing left.

Also, after a 400 cal cardio session it is hard to say how much glycogen you used since there is always a combination of glycogen and fat being burned. The more aerobiclly fit one is the more fat will be burned as opposed to glycogen.

sixisCHANGEDjk

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ttkg

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Aseymour68

Razz / Pu_239 (or any other insightful help)

I am 209 with about 20# I would like to lose. However, I am also committed to gaining a more refined muscular shape. Currently, I mix about 30 minutes cardio (running / elliptical) with about 30 min of strength training targeting different muscle groups 3-4 times weekly or every other day. . MFP has me on a 1500 calorie intake for the weight loss, which I have committed to. I eat focused on calorie but with foods that produce growth and muscle repair also.
As far as your comments are concerned, should I lower my cardio once I hit my weight goal and focus more on strength training if I want the results I am after? Would splitting up my cardio / strength days have the same effect that I am seeing now as far as weight loss?
My main question in the above is I want the weight loss without losing to much muscle mass. Is my cardio defeating my strength training on a 1500 calorie intake?

Thanks in advance for your thoughts.

lyn267

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scottb81

If there is roughly total 2000cals of glycogen stores in my muscles + liver, presuming I do eat carbs to replenish these and am not in a ridiculously low deficit, why then can we not do say, for example, a 300cal strength session followed by a 400cal cardio session? are there still 1300cals of glycogen sitting in the muscles ready to be used for repair + general movement?

If you eat properly, you will replace all your glycogen stores within 24 hours, even after a very hard exercise session.

If you do not eat properly then you will gradually deplete them until there is nothing left.

Also, after a 400 cal cardio session it is hard to say how much glycogen you used since there is always a combination of glycogen and fat being burned. The more aerobiclly fit one is the more fat will be burned as opposed to glycogen.

From my understanding we can only replenish glycogen at 5% per hour, doesn't matter how many carbs you eat. Elite athletes can replenish it at 10% per hour.

Well, at 5% per hour you will back at 100% in 20 hours or less depending on how depleted you are.

crisanderson27

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chezileigh

I disagree on the "what does work for some doesn't work for others" regarding the fiber involved.

he's right about this part for sure, physiology is physiology and although to some degree each human being is different, the net effect would be similar.

I don't know enough about exercise physiology to know whether what he's saying overall is right but he surely sounds like he knows what he's talking about.

thanks for the interesting post.

mmapags

Razique, you are holding out on me man! You send me links when you put up good stuff like this and you left me out in this one! I had to find it all by myself!

I agree that both are useful but not on the same day. Both intense lifting and higher intensity cardio cause a need for recovery and both on the same day overloads the CNS and causes competiion for recovery resources. Lower intensity is fine as is 5 to 10 minutes of warm up/ cool down for lifting.

GCNerd

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mtread13

Interesting stuff - while I get that that strength training and cardio fitness are somewhat in conflict, I'm confused as to how you'd recommend applying that if you want to improve both (over the long term). If one starts as an active, but overweight person who wants overall fitness and versatility, what would you do?

I'm doing P90X, which seems to mix the two and I'm already seeing performance results (for example, strength when I sling bags of mulch in working in the yard) and stamina (running with the kids).

I want to be someone who could do a 5K, play tennis, hike/climb, play sand v-ball, bike, play tennis, play soccer, cut wood all day, swim/surf all day, etc. -- well rounded, I guess. While as, an older fat guy, it seems a stretch - aesthetically, I'd like to imagine working towards looking like the people who play gladiators on film versus the more gaunt looking distance runners OR the thicker looking body-builders.

It seems like P90X, boot camps (military and gym based), training for actors playing those physical/buff looking action roles mix strength and cardio - does this only become an issue once you get far enough along in fitness? And once at that stage, do you go in cycles - strength train and diet for muscle mass for a few months and then shift back to cardio/circuit based training for a couple of months -- does this up the bar in both areas over time?

mmapags

I gotta be honest, I'm not a fan of PX 90 or other workouts of that style. They seem to burn people out and lead to non compliance and disouragement. I am similar to you in age and goals. I do strength 3 days per week using stronglifts 5x5, I do one session of HIIT per week and 2 longer cardio sessions, usually riding my bike for 12 to 18 miles but sometimes running. I do 2 rest days per week and I take more if I'm getting into overtraining eg, 2 weeks ago I did a 12 mile bike ride on Friday afternoon, a strength session on Saturday, a 16 mile bike ride on Sunday and a strength session on Monday. By Tuesday, I was wiped out. Shoulda stopped one day sooner and taken a rest day. That cost me 2 days off. Not horrible but I felt miserable all day Tuesday.

PS; Yeah I know if you add up my days it comes to 8. I just don't get too hung up on the schedule and try to make sure I leave in enough rest so when I train, I can get after it!