Circuit training

Circuit training is a popular way to train and can be adapted to focus on either cardiovascular workouts or strength training. Indoor training doing just one thing (like stairs) can be really boring so having a mixture of exercises can help motivate you. In addition, especially for trail running, you can work a variety of muscle groups to help prepare you for being out on the trails. Here is a combination of exercises that you can do with no extra tools that can help keep you fit and ready for the trails:

• Stairs - running up and down stairs is comparable to running up and down hills/mountains. Varying the number of stairs you touch on the way down is also good descending practice, provided you can do so safely.
  

• Step-ups - like stairs this mimics to a good extent the action of running up hill; again varying the number of stairs/height of the step up is a good way to increase your ability to clamber up rocky terrain.
  

• Star Jumps - going from a crouched position up into the stair jump works both your legs and your arms; the coordination involved is also helpful brain training for running on difficult terrain.
  

• Skipping with a rope - using a variety of hops, fast skips and alternate legs is good cardio and strength training combined with coordination training of jumping over the rope.
  

• Hop and stick - this is a great exercise for increasing both your balance and ankle strength - essential for good descending.
  

• Jumping - if you can focus on landing mid foot, dropping but not striking the heal and rolling through the foot and pushing off with the toes is good practice of the stretch/reflex action needed in the calves for running efficiency. Once you have perfected the above jumping action, you could try hopping as a progression.
  

• Jumping up one (or two) stairs from the standing position with feet together.
  

• Burpees - like star jumps this is a good combination of coordination, strength and cardio exercise.
  

• High knees - if you focus on keeping your back straight and head upright whilst performing this action as quickly as possibly not only will you be working your heart, you will be practising the quick action needed to reduce the time your foot is in contact with the ground when you are running