Time vs Effort at the gym

September 9, 2012 12:09 PM

Exercise n00b here. For strength training, is it better to A) work the muscle to exhaustion, or B) work the muscle for a long time? (I have asked my physical therapists and received conflicting answers, hence this question.)

(For context: I'm doing PT after a back injury, and need to increase my core strength and stability to help prevent the problem recurring. I'm not at all interested in weight loss or visible musculature, nor do I particularly care about aerobic benefits -- I'm in reasonably good shape in that sense -- my only goal here is reducing stress on my spinal column.)

So, for example, I can very quickly exhaust my abdominal muscles by lifting and holding a crunch position for longish periods of time; or I can do a whole bunch of crunches and have to spend a lot of time at it to feel like I've done the same amount of work.

For my purposes is one of these methods substantially better than the other? (My inclination is to get them over with quickly, because I'm more likely to actually do the exercises than if I have to block out a big chunk of the day for them, but I want to make sure that it's not wasted effort if I do it that way.)

posted by ook to sports, hobbies, & recreation (11 answers total)

Holding a single position does not work as much of the muscle or as many supporting muscles as working through a whole range of motion. It's not terrible, but for your purposes full movements will be better. (This is of course why it wears you out faster - it's putting more stress on a smaller part of a system.)
posted by restless_nomad at 12:14 PM on September 9, 2012

I went through a period where I was reading and talking about this a lot (well, I was looking at heavy weights/low reps vs. light weights/high reps but I think it's the same sort of thing you're getting at) and my takeaway was that heavy weights to exhaustion was better (my personal trainer at the time also had that belief and I played devil's advocate for a long time, trying to get him to offer ample support for his stance). I don't have time to find some good links at the moment, but here is a good start.

If you are working with a back injury there may be exceptions to this.
posted by triggerfinger at 12:21 PM on September 9, 2012

Convention states that heavy load until exhaustion (i.e., few repetitions) builds strength and light load until exhaustion (i.e., many repetitions) builds stamina. You're working until failure in both cases. If you aren't reaching the point of failure at the end of the last set, increase the resistance or the number of repetitions, depending on your goal.
posted by Nomyte at 12:30 PM on September 9, 2012

It really depends on what you're working and for what purpose. For example, for training the stabilizing muscles of the spinal column you want to focus on isometric exercises and exercises that require constant contraction. Things like planks, glute bridges, dead bugs, stir-the-pot, and bird-dogs will help engage and strengthen your deep core muscles. Rollouts are an excellent (though more advanced) move for this. Stuff like hanging leg raises and landmines make a good addendum to your program once you've progressed past those basic movements. Laying crunches and sit-ups, whether dynamic or isometric, are quite awful for your lower back, and virtually useless for building core strength so I'm pretty surprised any quality PT would ever recommend them.

A program addressing lower back pain relief and improvements in core stability shouldn't just be addressing core exercises, either. 90% of the time people who come in with lower back pain who haven't suffered an acute injury* are suffering from weak, inactive glutes, weak hams, and tight hip flexors. The combination of the three mean your lower back is now taking more load than it should and will be prone to injury and chronic pain. So it is worth doing a Google for "glute activation" exercises and drilling those as well to get those muscles firing. Stuff like squats and deads will help but if your motor patterns are borked you'll just end up doing them wrong and making the problem worse.


*Furthermore, a significant number of acute lower back injuries incurred at the gym or during physical activities have their root in the not-firing hams-and-glutes and tight hip flexor problem. Dysfunction in that area --> poor form in the gym --> bad loading on the lower back --> injury
posted by schroedinger at 12:50 PM on September 9, 2012 [13 favorites]

I guess I should also mention that the posterior chain issues can result in general back pain as well, not just lower, lower back pain just happens to be pretty closely tied.
posted by schroedinger at 12:51 PM on September 9, 2012

The strongest men are outside the gym. They are farmers, herders/cowboys, ocean fishermen. When you see how they physically exert themselves, I realize all my 'hard core' gym training looked silly.

They work past muscle in exhaustion.

If you have time, work a longer rep towards exhaustion. If you don't have time, more weight, quicker exertion, leading to quicker point of exhaustion. Depends on the amount of time you have at your disposal.
posted by Kruger5 at 1:39 PM on September 9, 2012

For the type of isometric exercises generally given by PTs, you'll get the most benefit from slow, steady motion and focusing on proper form.

The best way to get the most benefit in the least time is to make sure to use slow, controlled motion in both directions of the exercise. So if you're doing crunches, your progress should be:

1. Slowly roll up
2. Pause at the top of the motion to ensure your spine is properly aligned and the correct muscles are working,
3. Slowly roll down (do not let gravity do the work!)
4. Pause again to release any tension and ensure you are back to a neutral position

By contrast, if you do a quick succession of crunches, you're most likely letting gravity do the work in the down direction (no benefit), using momentum to carry you into the first section of the upward motion (little benefit) and only working your muscles fully for the brief hold at the top. So it will take more time to get to the same level of effort.

Finally, the most important thing to keep in mind for rehabilitative exercises is proper form! Your PT should be retraining your body not simply to build strength, but to ensure the proper muscle groups are providing power for each action, in a way that minimizes stress on your spine. If you're not paying attention to form, you'll simply be retraining your body to move in the same way that caused the injury in the first place. It is much, much better to do a few exercises slowly but properly than race through what the PT prescribed just to say you've done it.
posted by psycheslamp at 1:43 PM on September 9, 2012

I agree with restless_nomad that isometrics work the particular muscle more intensely, because moving through a range of motion means using different muscles at different parts of the movement and thus giving each muscle a chance to rest. But I would say that's a reason to do a few different isometrics, not a reason to avoid isometrics. Here's a neat little core strength program that gymnasts consider a warm-up:

60s plank
60s reverse plank
60s perfect hollow hold with hands over your head
60s arch hold in the superman flying position
60s Parallel Bar support.
60s chin up grip dead hang

If, like me, you can't do all sixty seconds in one set, just break it up into however many sets you need to total sixty seconds.

Variations: The support and hang can be done with the legs straight down, or with the knees raised up (tuck), or with the legs horizontal (pike), in order of ascending difficulty. The plank can be done on one leg, either straight or bent, and the opposite straight arm. The reverse plank can be done on one bent leg and two straight arms.
posted by d. z. wang at 2:30 PM on September 9, 2012 [4 favorites]

I would like to clarify that I was talking solely about situps - I agree with schroedinger and d.z. wang that there are a variety of exercises to look into and a decent PT should give you a broader program. Isometrics aren't bad in themselves, I just wouldn't do isometric crunches to stabilize your spine.
posted by restless_nomad at 2:42 PM on September 9, 2012 [1 favorite]

My inclination is to get them over with quickly, because I'm more likely to actually do the exercises

Assuming there's a physical therapist in the picture to make sure you're not doing something terrible to your back by mistake, it seems to me this is a more important consideration than the slightly different results of high/low reps or whatever. Exercises you actually do beat exercises you don't actually do. Maybe do the more time-consuming version periodically as a change of pace.
posted by hattifattener at 2:45 PM on September 9, 2012

Thanks, everyone -- lots of good advice here, I appreciate it!
posted by ook at 5:21 AM on September 10, 2012