As I mentioned in a previous blog, I was selected to participate in the Precision Nutrition Informal 8-Week Training Experiment.
I said that I would report the results of the study, and here - with the help of Helen Kollias of Precision Nutrition, Alwyn Cosgrove and myself - are the results.
In this study, we asked three questions. Which of these three programs:
-would most effectively improve performance?
-would most effectively promote weight loss?
-would people find most fun, and thus, stick with the longest?
We compared the programs based on two indicators: body weight and performance.
Assessing body weight was easy: Participants simply recorded their weight once a week during the study. By the end of the study, we had nine body weight measurements to compare from week 0 to the end of week 8.
Measuring performance was a little more intensive. Before the study began, and after it ended, everyone did the following five performance tests:
1. Maximal push-up test
2. Inverted row test
3. Standing broad jump test
4. Treadmill V-max test
5. Treadmill T-max test
Thus, at the end of the study, we had before/after body weight measures as well as before/after performance changes to compare between groups for the entire 8-week study.
Who Was in the Study?
On average, participants in all three groups were in their early to mid-30's, although we had participants up to 70 years old (see table 1).
Table 1 – Average age (in years) of participants
Steady-state cardioNote: Once the participants were selected to participate in the study, they were matched and assigned to groups (I was in the interval training group) based on gender, age, weight and training experience. This meant that the groups were very similar to begin with, so any measured effects should be the result of the training intervention rather than individual differences.
N = 17
Male = 35 +/- 6
Female = 34 +/- 11
Combined = 35 +/- 9
Interval cardio (I was in this group - I turned 34 going into this study)
N = 23
Male = 36.8 +/- 8.
Female = 31.0 +/- 6.8
Combined = 35.0 +/-8.1
N = 16
Male = 33.2 +/- 7.3
Female = 36.4 +/- 8.1
Combined = 34.6 +/-7.6
Our participants had an average of 9 years' exercise experience (I have more than 15 years' experience). These people knew their way around the gym.
A Few More Things…
We wanted to make sure that the results reflected the exercise program, not other factors. So we asked our participants to make a few sacrifices in the name of science.
First, although we didn't have any dietary restrictions for the participants, we did ask anyone who was currently on a "bulking" diet (weight-gaining diet) to exclude themselves from the study or modify their diet.
Second, the participants couldn't do any other physical activities except activities required for everyday life.
Finally, anybody who had specific, short-term performance or body composition goals (such as a 5k race or a figure competition) were discouraged from participating, as this program was a general, not a targeted, plan. And we wanted to measure what our intervention alone could do.
What Happened: Weight Loss
Interestingly, those in all three groups lost weight. Indeed, after 8 weeks, the average weight loss was about 3.2 lbs with no statistical differences between genders or groups. In other words, although all groups lost weight, any apparent differences in table 2 below are likely due to random chance rather than real differences.
Table 2 – Average weight loss (in pounds) over 8 weeks
Male = -3.4 +/- 4.4
Female = -4.9 +/- 4
Combined = -4 +/-4.1
Male = -2.9 +/- 3.8
Female = -0.6 +/- 2.2
Combined = -1.8 +/- 3.7
*I actually gained 6lbs in the first several weeks but then lost a few pounds during the last few weeks showing a net gain of 3lbs at the end of the 8 weeks!
Male = +4.2 +/- 5.1
Female = -1.1 +/- 3.2
Combined = -2.8 +/- 4.5
What Happened: Performance
Along with weight loss, every group improved their performance — often impressively. (High fives to Alwyn.) But there were no statistical differences between genders or groups; remember, they all did the same strength workouts.
Table 3 – Average change in push-ups after 8 weeks
Male = +9.8 +/- 7.2
Female = +11.7 +/- 5.5
Combined = +10.7 +/- 6.3
Male = +10.1 +/- 6.9
Female = +2.7 +/- 6.7
Combined = +7.9 +/- 7.5
*I increased my pushups by 4.
Male = +12.4 +/- 9.4
Female = +6.2 +/- 3.5
Combined = +9.8 +/- 7.9
Table 4 – Average change in inverted rows after 8 weeks
Male = +4.8 +/- 2.0
Female = +6.9 +/-6.5
Combined = +5.7 +/- 4.6
Male = +5.1 +/- 3.8
Female = +2.9 +/-1.2
Combined = +4.4 +/-3.3
*I increased my inverted rows by one rep.
Male = +6.8 +/- 4.5
Female = +2.9 +/- 1.6
Combined = +5.1 +/-4.0
Table 5 – Average change in broad jump distance (in cm) after 8 weeks
Male = +6.2 +/- 6.5
Female = +5.0 +/- 3.7
Combined = +5.7 +/- 5.3
Male = +4.1 +/- 9.4
Female = +6.4 +/- 6.9
Combined = +4.7 +/- 8.7
*I had a 3-inch gain.
Male = +4.8 +/- 3.0
Female = 2.6 +/-4.4
Combined = +3.8 +/- 3.8
Table 6 – Average change in V-max (% grade at constant speed) after 8 weeks
Male = +1.2 +/- 1.2
Female = +1.7 +/- 1.1
Combined = +1.4 +/- 1.2
Male = +1.4 +/- 0.9
Female = +1.9 +/- 1.1
Combined = +1.5 +/- 1.0
*I increased from 7mph at 5% incline to 7mph at 7% incline.
Male = +1.4 +/- 0.6
Female = +0.3 +/- 0.5
Combined = +0.9 +/- 0.8
Table 7 – Average change in T-max (in seconds) after 8 weeks
Male = +128.0 +/- 156.4
Female = +193.4 +/- 145.3
Combined = +160.7 +/- 149.0
Male = +80.7 +/- 123.6
Female = +0 +/- 43
Combined = +53.9 +/- 112.3
*I actually had a decrease of 60 seconds but it was at the higher incline (7% instead of 5%).
Male = +78.7 +/- 118.9
Female = +37.4 +/-63.9
Combined = +60.75 +/- 98.1
While there wasn’t much of a difference between groups as far as weight loss and performance, we noticed a huge difference in the study drop-out rate. Steady-state cardio had a very high drop-out rate, while the TRX group participants were most likely to finish the study.
Table 8 – Drop-out rate
Steady-state cardio - 80%
Interval cardio - 55%
TRX group - 35%
Most research labs never have this sort of dropout rate. Because subjects are paid to participate and because they have to report to real-life people, they finish what they start. However, because our Informal Experiments are unpaid and distance-based, it's easy for participants to blow us off.
Sure, a few will let us know if something happened to exclude them from finishing. However, many of them simply ignore our emails. Even if we were kind enough to send them a workout plan — or even a TRX suspension trainer. Shame, shame. But, no matter. This is what explains the higher drop-out rates seen in a study like this.
However, we're not sure what explains the higher drop-out rate in the steady-state cardio group. For starters, five people in the steady-state group dropped out the day they received their programs. We figured this was because they assumed steady-state cardio sucks (which it does not, when combined with a good strength program). Again, shame, shame.
Of course, injuries are another possibility. But we didn't get more emails from the steady-state groups saying they were injured. For the most part, any injuries were evenly distributed and mostly non-exercise related (for example, we got a picture of a bruised toe to prove a ladder accident story.) So we doubt that was the problem.
The final explanation could be — simply — that steady-state cardio is kinda boring. Not everyone loves the idea of walking on a treadmill for 45 minutes. (Personal trainers everywhere, are you listening?)
All groups saw equal improvements in performance and weight lost. At least, statistically speaking. If you ask me, these improvements were excellent. For example, after just two months following the prescribed programs, participants improved their performance by an average of 30%.
This is especially awesome considering that, on average, these people had over 9 years' exercise experience. Why does this matter? The vast majority of exercise studies use participants with no training experience (untrained). And anybody who has trained can tell you that in the beginning you get the biggest improvement.
And yet, in this study, people who had already been exercising for over 9 years saw up to 30% improvement in some performance measures (push-ups, inverted row and T-max) in 8 weeks!
Why No Difference Between Groups?
Now, you probably noticed that for push-ups, rows, broad jumps, and V-max, the group means were pretty similar. That’s not unexpected.
While there is literature out there showing the effectiveness of interval training and other types of conditioning exercise vs. steady-state cardio for weight and fat changes, there isn't really any data showing that with a properly designed cross-training program, we should expect differences in key performance variables.
The steady-state group did seem to have better T-max scores. Now, again, statistically, there was no difference between groups. However, if there were a slight trend toward a higher T-max, a surrogate marker of anaerobic threshold and aerobic fitness, we would expect the groups that spent the most time on the treadmill to do the best.
So, what's the take home? Well, around here, most of us do interval training and circuit training (similar to the TRX work) for our conditioning exercise because we find theses types of exercises more challenging, and far more interesting than steady state cardio work.
Maybe this type of training just brings out the masochists in us; we usually alternate between states of:
- Trying to survive the work interval without flying off the treadmill or getting tangled in our TRX
- Dreading the end of the rest interval, thinking, "Is there something wrong with my watch?"
So, while the performance numbers weren't really different between groups, something more important was: actually doing the workouts. Remember, 80% of the people in the steady-state group dropped out. 55% dropped out in the interval group. And only 35% dropped out in the TRX group.
As Woody Allen said, "80% of success is just showing up."
Participants lost, on average, 3-5 lbs without changing their diets. And if you think this isn't much, think again. Resent research has shown that exercise alone isn't very effective without some sort of nutritional change. In fact, many studies have shown no change if a nutrition plan isn't implemented. Check out this article for more.
The simple fact that weight loss occurred in all three groups of experienced exercisers is very cool.
Why No Difference Between Groups?
Although many people have pooh-poohed steady-state cardio for the last few years, when combined with a solid strength training program, steady state cardio can help folks lose weight and improve performance.
That's right: steady state cardio + strength training has been used – with much success – by physique champions for decades. It works. As does interval work + strength training. As does TRX work + strength training.
Thus, we weren't surprised at all that there were no differences between groups in terms of weight loss or performance. After all, they did about the same total duration of exercise – 4 sessions per week; 2×45 min strength sessions and 2×30-45 min conditioning sessions. So, when total workout times were equated, why should we expect to see anything different?
Now, we don't have body composition data, as described above. Had we collected those data, perhaps we'd have seen more subtle changes in fat mass and lean mass.
But, truthfully, I doubt it. All three programs included a strength training program and a similar volume of exercise. We have no reason to believe more muscle would have been built and fat lost with any specific intervention.
The Bottom Line
Here's how to interpret these results:
When you equate total exercise time, as long as you're doing an intense, progressive strength + conditioning exercise program, you can feel free to choose whichever program you like best.
If you prefer steady-state work, add it in. If you prefer interval work, add it in. And if you prefer TRX style workouts, add them in. Indeed, in this study, participants seemed to prefer the TRX style workouts. They loved the diversity and intensity associated with this program.
Of course, to do these workouts, you'd obviously need a TRX suspension trainer. Here's how you can get one:
TRX suspension trainer
And once you have your TRX system, know that as long as you have a great strength training program, feel free to add in steady-state cardio, TRX circuits, and sprint intervals to your heart's content.
Alwyn Cosgrove's comments:
I was actually a wee bit surprised with the results.
All the studies published on body composition show weight training to be superior to cardio, and interval training to be superior to steady state.
So I was expecting to see a clearer difference - but I guess the strength program in addition changes everything. Or at least the way I designed it (with supersets and short rest periods) had an effect.
I didn't see the TRX program until after I'd written the strength program, so there may have been some interference as there was some overlap between movements.
The drop out rate surprised me too. Like the PN guys said - it's an informal experiment but there is a real-world take home message for fitness professionals there.
One of the very interesting things was that the TRX group demonstrated similar improvements in running performance as both the interval training and steady-state groups. Without doing any running! That's a pretty good result.
I'd also like to have seen a group that did my program only, to see what those results alone were.
Informally - Right now our number one body comp program is two days strength, two days metabolic (combo of intervals, BW, KB's and TRX). We tested it against resistance training and traditional cardio and it was more effective in terms of pure body comp numbers.
(We also just had a group of women go through a 4-week cycle of TRX only training)
Overall, it was very cool to be involved with JB, the Precision Nutrition team and Fraser, and I look forward to doing more work with them.
I was also surprised that there wasn't a more distinct difference in performance between the three groups. As Alwyn mentioned, this may be due to the resistance training program that he designed.
Although some of my performance numbers weren't as high as the other males or the combined numbers for each group, they were all increases from the beginning of the program. Considering that I began training more than 15 years ago, those are some good improvements in a short period of time.
The fact that I gained weight almost as soon as I started the training experiment and for the first four weeks into the program is due to two things:
- I was performing less total exercise than what I was previously doing
- I had not reduced my caloric intake when I began the program
The biggest take-home point to this experiment is what Helen mentioned previously:
"When you equate total exercise time, as long as you're doing an intense, progressive strength + conditioning exercise program, you can feel free to choose whichever program you like best."
As I've said before, "Everything works. Nothing works forever."
When it comes to training, you have to find the things you enjoy doing but that also give you results. If you have plenty of time to exercise, then resistance training and steady-state cardio will work. If you are more time challenged, then resistance training and interval training or TRX circuits will work.
It all depends on your goals, the time you have available to train, your training experience, your compliance (fun factor) and your adherence to a proper nutritional program.