If your goal is simply to stay fit ad healthy, these shortyet thorough workouts will boost heart health, build bone density and strengthen muscles.
"Runners often think that the more they run, the healthier they'll be," says Bill Pierce, co-founder of the Furman Institute of Running and Scientific Training in South Carolina, US. But that can increase your risk of injury.
"To stay healthy, target areas of fitness you normally don't pay attention to - like flexibility and strength," says Pierce. During the run portion of these workouts, for every two minutes of hard effort, beginners should walk for one minute, gradually increasing the length of the hard efforts.
You've got...20 minutes
You should: Perform an 'envelope run'
This drill run builds in intensity, then peaks and slows. "Vigorous exercise yields the greatest health benefits," says Pierce.
Do drills, then pick up the pace. Jog for five minutes and do 25m each of knee lifts and rear kicks. Then, for five minutes, increase your speed until it feels hard. Maintain that pace for another five minutes, or go slightly faster if you can. Cool down for five minutes.
You've got...30 minutes
You should: Combine an envelope run with body-weight resistance training
"Maintaining muscle mass and building core strength for good posture will help prevent injuries," says Pierce.
After doing the envelope run (above), do two sets of the following: 30 seconds each of press-ups, squats and crunches; 60 seconds of planks and calf raises; 90 seconds of walking lunges.
You've got...45 minutes
You should: Do an envelope run, body-weight resistance training and stretching
Adding flexibility work increases range of motion, which decreases injury risk and improves alignment, says Pierce.
Add five minutes each to the envelope run and resistance routines Afterwards, do five quick stretches. Hold each stretch for 30 seconds per leg.
You've got...An hour (or more)
You Should: Combine a tempo run with resistance training and stretches
"These ancillary exercises help correct muscle imbalances," says Pierce.
Increase your pace to 30 seconds slower than 5K race pace run at this speed for 20 minutes. (Warm up and cool down for five minutes each.) Do two sets of the five quick stretches, then spend five minutes on these five key exercises for a full workout.
Time for change
What to do when you're not up for a run
Sometimes, you just don't feel like running. Great! That's the perfect time to do something else. "I advocate cross-training for all runners," says Pierce. "It strengthens underused muscles and keeps your body - and mind - fresh so you're ready for a high-quality effort on running days." The effort level recommended in each workout below mimics the effort of running at a moderate pace - or a little slower than a tempo run.
You've got 20 minutes: Hit the rowing machine at the gym. Aim for an effort that feels like a 7 or 8 on a scale of 1-10.
You've got 30 minutes: Ride a bike at around 90 revolutions per minute (to calculate, count how many times your right knee comes up in 10 seconds and multiply by six).
You've got 45 minutes: Swim 25m hard, then 25m easy; repeat until the time is up.
You've got 60+ minutes: Use your gym's cross-trainer at an effort that feels like a 7 or 8 on a scale of 1-10.