Gyms get pretty crowded this time of year, and can often be very expensive, but you don't need one to get in shape - there's more fun to be had outdoors anyway. Here's a few ways to get fit without gym membership in 2015.
Try new activities
Hiking shouldn't be underestimated as an endurance and stamina-building sport. It's a great way to keep fit without having to queue to use fitness equipment in an airless gym. If you're based in the UK, you're rarely very far from a group of Ramblers organising regular walks (and sometimes offering lifts too). This terrific nationwide charity organises walks at all levels of ability, including regular strenuous hikes. If you prefer to strike out alone, all you need to get started are sturdy boots... although consider taking some lightweight waterproofs too.
If you're more adventurous, you'll find that climbing either indoors or outdoors works muscles you never realised that you had. Even regular gym-bunnies will find a climbing session surprisingly strenuous when they first get started.
The sport requires special rubber-sided shoes - make sure you get a snug fit as they need to be close against your feet. You may prefer to start at lower lever with 'bouldering' on a low-height climbing wall before moving onto rope-climbing. Climbers tend to be a friendly bunch, so start out with a class at your local climbing centre to make sure you've got the basic skills.
Try Nordic Walking - it's like an intensive form of power walking that can use over 40% more energy than regular walking. You don't need much training or equipment: just good walking footwear and a pair of walking poles like the Vango Classic Walking Pole.
If you're serious about high-intensity activity, see if you're brave enough to try fell running. It's been described as 'cross-country running on steroids' and involves splashing through puddles, up mountains, through bogs, crags and heather.
You just need a sturdy pair of shoes with a good gripping sole for running offroad - and access to the open countryside of places like Wales or the Lake District. If you can access the location, fell running tends to offer a great community spirit and entry to events is usually good value.