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When researchers at McMaster University pooled the results of nearly 200 strength training studies with more than 5,000 participants, they reached a surprising conclusion. The details of how much weight, how many sets and how often people worked out had only a minor impact on how much muscle they gained.

“The biggest variable to master is compliance,” Jonathan Mcleod, the study’s co-lead author, said in a press release. “Once you’ve got that down, then you can worry about all of the other subtle nuances.”

That’s an observation that rings true across the exercise spectrum, whether you’re training for a marathon, hitting the weights or simply trying to improve your health. The details of what you do matter less than whether you stick with a routine consistently over the long haul.

But what determines who complies and who drops out of fitness programs remains a hotly debated topic among exercise scientists.

In the Translational Journal of the American College of Sports Medicine, Duke University exercise physiologist Katherine Collins and her colleagues crunched data from nearly 1,000 overweight participants who enrolled in six- to eight-month supervised exercise regimens, zeroing in for the first time on when people drop out.

The study included ten different exercise programs of varying intensities and exercise types. The duration and frequency of workouts also varied.

Overall, about 30 per cent of the initially enrolled subjects failed to complete their full exercise program, which is a fairly typical dropout rate. As in the McMaster study, the details of the assigned program had little impact on the outcome: it wasn’t a particular combination of intensities or durations that led people to quit.

It’s time to stop picking sides in the cardio vs. weightlifting debate

Instead, the most notable finding was that ⅔ of the dropouts occurred during the initial stages of the study, before the exercise programs had even ramped up to their full intensity. The most common reason for stopping, given by 40 per cent of participants, was a lack of time. Of those who made it through the initial ramp-up period, the vast majority stuck with the program all the way to the finish.

One of the big debates about exercise compliance is between those who believe lack of time is the reason so many adults fail to get enough exercise, and those who believe other reasons such as a lack of enjoyment are more important.

If time is the problem, then short high-intensity interval workouts are a good solution. But if the real issue is that people don’t enjoy their workouts, then prescribing gut-busting intervals may backfire.

On the surface, Dr. Collins’s results support the view that time is a major barrier – but she added a note of caution. “I think lack of time is a very relative term that people use because they may not exactly know why they do not want to participate anymore,” she explained in an e-mail. “Saying they don’t have time is a rational and socially acceptable reason to state.”

Those who dropped out tended to be slightly less fit at the start of the study, suggesting that the ramp-up workouts may have been too aggressive. Dr. Collins’s takeaway is that the initial stages of an exercise program are when people are most vulnerable to quitting, so trainers need to be especially attuned to adjusting the workouts to keep them feasible.

“However,” she added, “I also think addressing barriers and support systems upfront is just as important as the physical requirements of exercise.”

For some, time may really be the limiting factor. For others, it may be confidence in their abilities, or a lack of peer support or nagging injuries. There’s no single barrier that explains all dropouts, and so there’s no single solution that will solve the challenge of keeping people engaged in exercise.

There is, however, one piece of good news to keep in mind. As the McMaster strength-training data demonstrates, and as the broad diversity of exercise routines used around the world confirms, you don’t need to worry that you’re lifting the wrong weight or doing the wrong number of sets.

The secret formula is showing up in the first place.

Alex Hutchinson is the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. Follow him on Twitter @sweatscience.

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