Some days you're so rushed for time that it's nearly impossible to get your regular workout in. But rather than write off the day altogether, consider slotting in a condensed 20-minute training session.

That's for beginners, you say? Not if you use the most of your time by increasing the workout intensity. All you have to do is follow the plan, move quickly, and work hard. You still need to accumulate volume over the course of those 20 minutes if you want to make physique gains. One or two short workouts per week won't make you fit.

The "get in, get out" mentality can pay great dividends if you keep the frequency and intensity up. You'll aim for 4-6 short intense workouts per week, chosen from the following categories, all of which give great bang for the buck.

• Mid-Range Strength Workouts (3 to choose from)
• Complexes (3 to choose from)
• Challenges (2 to choose from)
• Conditioning (3 to choose from)

1. Mid-Range Strength Workouts

I love performing multi-joint exercises in the 5-8-rep range. If you really challenge yourself with weight, it can produce a combination of size and strength unrivaled by other rep ranges.

Try the following three workouts, rotating them to work different target muscle groups.

2. Complexes

A metabolic complex is a series of exercises performed fluidly together without rest. Complexes are ideal for fat loss. They involve tremendous amounts of work in a short time. For the time-crunched, complexes are invaluable.

Some of the following exercises that are included can be a bit advanced, the hang clean being one example. But in a complex we aren't stressing flawless, Olympic-quality technique.

Rather, we're looking for a safe, quality rep that works. If you're not a pro at cleans, don't sweat it—just get the basics down. Be explosive, hinge at the hips, keep a neutral spine and use your whole body to propel the weight.

Remember, the goal is to move weight for a lot of reps in a short amount of time. Because of this goal, your weights won't be all that high. A good benchmark is to use a weight you can press or push-press overhead for 10 repetitions.

Barbell Complex

• Choose a weight at which you can perform 10 overhead presses—you'll use that weight on all exercises.
• Perform 6 repetitions of each without resting—this is one cycle.
• Rest 90 seconds between cycles.
• Repeat 5 times.

Dumbbell Complex

• Choose a weight with which you can perform 10 overhead presses. You'll use that weight on all exercises.
• Perform one rep of each exercise and then fluidly move to the next.
• Repeat all of the exercises in order a total of eight times; that's one cycle.
• Rest 90 seconds between cycles.
• Repeat 5 times.

12-8-40 Complex

• Men: Use a dumbbell weighing 50% of bodyweight for goblet squats.
• Women: Use dumbbell weighing 30% of bodyweight for goblet squats.

3. Challenges

A challenge entails doing as much work as possible in a set time period. This is a fun way to keep training fresh and intensity high. Choose multi-joint lifts and see how many reps you can complete before time elapses. Low-technique lifts are ideal, as heavy fatigue can make complicated lifts dangerous.

11-Minute Squats

Choose a weight that represents 30-40 percent of your 1RM back squat. Perform as many reps as possible, without racking the bar, in the time allotted. Perform two sets of eight goblet squats to warm up.

Push-Pull Challenge

Cycle through the following four exercises until you complete the target number of each. It will take at least eight cycles to reach your goal, but as fatigue sets in it may take 10-12.

4. Conditioning

In conditioning workouts, you'll stress locomotion—moving like an athlete. The workouts above will increase conditioning, but nothing replaces sprinting, cutting and jumping.

Agilities

Find a gym floor, grassy area or black top. Take five cones and set them up in any geometric shape you choose. Pick any combination of sprinting, backpedaling and shuffling between cones. All that matters is you move explosively, staying low with your chest puffed up and the back straight.

Hill Sprints

Find a hill with a moderate to steep incline of 20-40 yards in length. Wearing cleats is ideal. Sprint up the hill and time your sprint, then walk down. Once at the bottom, give yourself a 6:1 ratio of rest to work. So, if your sprint lasted 6 seconds, rest for about 35 seconds before going again. Repeat for 20 minutes.

Interval Runs

Distance running is not ideal for building a lean, muscular physique. But interval runs can be a good change of pace that won't burn up muscle tissue like steady-state cardio. The following schemes, performed for 20 minutes, are simple and effective:

• 30 seconds hard run, 60 seconds walk
• 45 seconds hard run, 90 seconds walk
• 30 seconds hard run, 90 seconds slow jog
• 45 seconds hard run, 120 seconds slow jog

Putting It All Together

Ideally, you can follow a five-day split. This would include two days of mid-range strength training, and one day each for complexes, challenge, and conditioning. If you have only four days available, skip the challenge or conditioning program. If you can afford six days, add a second day of complexes or conditioning.

Simply choose any workout from each category and go to it. If it sounds like there's a lot of squatting involved, you're right. Multi-joint exercises like the squat will provide the greatest whole-body stimulus, making it highly efficient.

If your legs are a little sore, simply reduce the load the next time out—but keep going. Your body will adapt.