I captain/coach an amateur level team: we can normally meet to practice only once a week, and usually are forced to choose between either focus on fundamentals, stategy, scrimmaging and similar instead of conditioning and working on athletic skills, or to end up using more than half of our time for that, resulting in better athletic condition but worse overall preparation. Players are between 18 and 30 years old (me being the one at almost 30), with varying levels of past sports experience: the most problematic ones in terms of independent training are usually the ones with less experience, regardless of age.
I would like to see every single player dedicate some of their own time to training, e.g. to do conditioning by running, body weight exercises, and so on. Many of them are not used to being involved in sports in general, so even if they try to stick to a training regime, they stop because of forgetfulness, laziness, or whatever else, in the course of 2/3 days.
Are there known methods to increase the players' motivation? I'm thinking for instance competitions among teammates and such. Examples from real experience are most welcome.