Not the usual recommendation
I recently saw some articles about making a vigorous workout once a week to reduce the time spent on exercise. This is an unusual suggestion is generally agreed that training should be more frequent, ideally at least 3 times a week. He leads a week once effective, however, and, more importantly, is there a risk?
The SCM Agreement recommends ...
For many years, a large number of tips fitness is based on the position stands of the American College of Sports Medicine (ACSM). Your current position in the frequency of exercise is that for cardio we do well:
• The work of moderate intensity for more than 30 minutes at least 5 times a week
• Work vigorously for 20 minutes or more at least 3 times a week
• or a combination of both for total energy expenditure 500-1000 MET minutes at least once a week
To get a rough idea, using the numbers of the Compendium of Physical Activities (https://sites.google.com/site/compendiumofphysicalactivities/Activity-Categories/running) 500 minutes MET would, for example, about 45 minutes of running in the 6.7 mph
With regard to the strength and flexibility training is recommended at least twice a week. This is because once a week would not be enough to maintain muscle adaptations induced by exercise, so it would be very little progress.
Is it safe?
Thus, on this basis, cardio at least, it seems that once a week is enough if you are willing to work hard. Very hard. The other thing to think about is whether there is a risk. I could find no reference to it, but I'd be worried that work vigorously once a week would be more likely to cause muscle pain, stiffness and damage more frequent exercise. Maybe this is not the setting of cases, young people, but I would say that no one should be careful to try this.
Conclusion - a good idea or not?
In general, I do not think it's good. For young people who want to maintain their cardiovascular fitness and do not have a lot of time that could be a good solution, but for overall fitness would have to do some strength and flexibility as well, plus an additional strength / Sign flexibility during the week. It would be better to opt for 20 minutes of vigorous exercise three times a week option, perhaps doing cardio / strength intervals.