It's been one of those days. Since the moment you hit the snooze button this morning you've been behind schedule. Now it's well past your normal workout time and you haven't even changed into your gym clothes. There's no way you can squeeze a beneficial strength workout into the 20-minutes still available to you. Or can you?

It is possible to get a great strength workout in less than half an hour. The key to getting out fitness gains in a short time is smart exercise selection.

Start by replacing 'isolation movements' that activate individual muscle groups (think hamstrings curls on the machine) with workouts featuring multi-joint movements ? such as squat variations ? that cover major muscle groups with fewer exercises.

Also, emphasize exercises that involve extension or retraction (such as row variations) rather than those that involve sitting, curling and flexing. And, build in variety and progression ? to make consistent progress, you need to change it up and keep challenging yourself.

The following 20-minute strength circuit combines five exercises that activate more than half the major muscle groups, so you still get a whole-body strength workout with just a handful of movements.

Another bonus? Each requires minimal set-up time and little or no equipment (at most a pair of dumbbells), so you can move quickly from one to the next.

The warm-up

No matter how hurried you are, be sure to take a few minutes to warm up properly. A good warm-up will prepare your body to perform the following strength exercises more efficiently and with less chance of injury. I recommend the following to warm up (aim for three minutes not stop):

• Running on the spot and varying the height of your knee


• Kickboxing with punches and kicks


• Skipping

The workout

After completing your warm-up, do the following five exercises in circuit fashion ? that is, complete each exercise one after the other without resting between them. Rest for one minute after you complete each full circuit, or, even better, perform a minute of the mobility exercises you did in your warm-up ? you'll get an extra benefit from the workout without making it any longer. Complete two to four total circuits.

1. Goblet Squat:

A great strengthener for the thighs, glutes, lower back and abs.

Stand with your feet slightly wider than shoulder-width apart. Grasp a dumbbell vertically with both hands, the top close to your chest or even resting lightly against it.

Push your hips backward, then bend your knees and lower your butt toward the floor.

Squat as deeply as you can without rounding your back or straining your hamstrings (the deeper you go, the stronger you?ll become throughout your full range of motion, but don't sacrifice good form to gain more depth).

Generate force from your hips as you press powerfully upward to return to the starting position.

Do eight to 10 repetitions using the heaviest weight you can lift with good form. Concentrate on keeping your chest high, and keep the dumbbell close to you at chest level ? don't let your arms drop or your knees go beyond your toes.

For a greater challenge, switch to another squat variation, such as the barbell back squat.

2. Push up: 

Works the chest, back, upper arms, shoulders and abdominal muscles.

Position your hands just outside shoulder-width apart. Imagine your body being a straight line from your ankles to the top of your head. Don't allow your hips to sag or your butt to stick up too high.

Tuck your chin slightly so your neck is in line with your spine. Lower your chest to within an inch or two of the floor. Look at the floor the entire time, and keep your core braced tightly. Press back to the starting position.

Do 10 to 20 repetitions. If you can't do at least 10 standard push ups, instead do elevated push ups with your hands positioned on an exercise bench. If you can do more than 20 push ups, do resisted push ups with a resistance band wrapped over your shoulder blades, the ends pressed to the floor under your hands.

3. Reverse Lunge:

Strengthens the hips, glutes, hamstrings and quads, and also recruits the abdominal stabilizers for balance.

Stand neutrally, your arms hanging at your sides. Take a long step backward with your right leg, keeping most of your weight on your left heel and maintaining an upright-torso posture. Use the left leg to decelerate your descent and propel your body back up to the starting position. That's one rep.

Complete eight to 10 repetitions with the right leg, and then work the left leg.

If you can complete more than 10 lunges, then do this exercise while holding a dumbbell in each hand. Use the heaviest dumbbells with which you can complete at least eight reps.

For an even greater challenge, perform an elevated reverse lunge, stepping down from an exercise step.

4. Plank:

Strengthens the abs, hips, lower back and glutes; increases endurance of spinal stabilizers.

Assume a standard push up position with your upper-body weight supported on your forearms instead of your palms. Maintain a 90-degree bend in your elbows and make sure they are placed directly underneath the shoulders so you have a strong base of support. Brace your core and glutes, keeping your hips in line with your legs and torso.