It's as simple as it is effective for developing strength and stamina. All you have to do is turn your car on, put it in neutral, and push it 'till you feel like crying.

Make sure you bring a friend with you to an empty parking lot so he can pump the brakes when needed. Car pushes are very similar to sled pushes in the gym, but they make you feel significantly more badass. Plus, if your car breaks down sometime in the future you'll have trained for that exact moment. Now that's functional strength!

Uphill sprints are a great way to develop the fast twitch fibers in your legs to keep you explosive and athletic. Running uphill is safer than running on a flat surface due to less impact on your joints and less eccentric demand placed on the hamstrings.

Arguably the greatest running back of all time, Walter Payton, was famous for including these in his outdoor workouts. And he was known for having powerful legs that could both outrun and punish defenders.

Similar to why running uphill is easier on your joints than running on a flat surface, jumping uphill is the same. Performing rapid fire, multiple broad jumps uphill is brutal on your lower body and incredibly taxing on the lungs.

Uphill jumps allow you to practice explosive triple extension (extension of the hips, knees, and ankles) without having to absorb as much of the load when you land. If you're still trying to be explosive, yet don't have access to a barbell or your normal gym equipment, these are a great substitute.