As anyone who works in a traditional (read: office) job environment knows, finding time to fit in fitness can be a challenge. But even if you can’t get to the gym, you can still keep your body strong. Everyone needs a repertoire of simple exercises they can do no matter what, says Keli Roberts, a trainer in Los Angeles and spokesperson for the American Council on Exercise. “It's easy to skip strength training if you can't get to the gym, but there are exercises you can do at home or on your lunch break,” says Keli. “They work the major muscles, and you don’t need machines."

In fact, that's what makes these exercises so ideal. With minimum equipment you get maximum results. And when you do develop a gym habit and have access to all your favorite machines, you can still do these exercises once or twice a week to maintain strength in your most important muscle groups: quadriceps, glutes, calves, biceps, shoulders and abs.

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Add in 30 minutes of moderate-intensity aerobic exercise on most days of the week—which you can break down into two 15-minute or three 10-minute sessions—and you’ll meet the recommended guidelines from the Centers for Disease Control and Prevention (CDC).

Several of the moves require dumbbell weights (though you can substitute inexpensive resistance bands in a pinch). Use heavy enough weights that the final few repetitions of a set feel challenging. When you're ready to use heavier weights, increase slowly to reduce risk of muscle injury. Do these moves at least three times a week. For the upper body exercises, increase the weights in 1- to 2-pound increments; for the lower body, increase in 3- to 5-pound increments.

Push-ups

Strengthens the pectoralis major and minor, triceps, and deltoids.

Get down on the floor on all fours. Place your hands on the ground directly under your shoulders. Point your thumbs in toward one another, elbows flared out to the sides, and walk your feet out behind you. Keeping your head in line with your spine and your abdominals contracted, inhale and bend your elbows so your body lowers toward the ground, your chest about two inches from the floor. Push back up to the starting position without hyperextending your elbows. Do 15 repetitions. If you can't complete the reps from the traditional push-up position, finish the set on your knees.

Make it harder: Put your feet on an aerobic step or the lowest stair of a staircase, and do your push-ups from an declined position. Be sure to keep your spine, neck, and head in a straight line.

Bent-over Rows

Strengthens the latissismus dorsi and biceps.

Hold a dumbbell in each hand with your palms facing inward (if you've never done this exercise before, start with 2- or 3-pound weights). Stand with your feet shoulder-width apart, knees bent, and bend forward from the hips. Squeeze your shoulder blades together, and allow your arms to hang straight down from your shoulders. Pull your navel in toward your spine, and, keeping your shoulder blades squeezed and your chest open, exhale and pull your elbows up and back until the weights are next to your ribs. Inhale and return to the starting position. Complete 12 to 15 repetitions. Work up to three sets.

Make it harder: Rotate the weight. As you lift the dumbbells, rotate your arms so that your palms face backward, a variation that puts extra emphasis on your biceps.

Side-arm Raises

Strengthens the deltoids.

Hold a dumbbell in each hand (if you've never done this exercise before, start with 2- or 3-pound weights). Stand with your feet shoulder-width apart and knees slightly bent. Pull your navel in toward your spine, contract your glutes (your butt), and drop your tailbone so your hips shift slightly forward. Lift your chest. Squeeze your shoulder blades together and raise your arms out the sides, keeping your elbows loose. Stop when the weights are shoulder height. Complete 12 to 15 reps. Work up to three sets.

Make it harder: After each set of side-arm raises, add a set of rear raises to target the backs of your shoulders and arms. Stand in the same position as above, holding the weights with palms facing in. Exhale and push your arms up behind you as high as you can. Pause and slowly lower the weights back down. Be sure to keep your body upright for the duration of the move.

Squats

Strengthens the gluteus maximus, gluteus minimus, quadriceps, and hamstrings.

Stand with your feet shoulder-width apart, toes pointing straight ahead. Pull your navel in toward your spine, relax your shoulders, and make sure your ears are in line with your shoulders. Inhale and bend your knees, shifting your weight slightly so your hips are behind your heels. Stop when your knees are over your toes—don't allow your knees to drift past your toes, which can lead to injury. Exhale and push yourself back the starting position. Be sure to keep your shoulder blades pulled down and back. At first, do this exercise without weight, but as you get stronger, hold a dumbbell in each hand while you do the exercise. Complete 12 to 15 repetitions. Work up to three sets.

Make it harder: Do plié squats (to work the adductor and abductor in the thighs). Stand with your feet out a little wider than in the regular squat, and angle your toes outward. This is called a “plié position.” Lower your body in the same way as you would for the traditional squat above. You may find that you can go lower this way since you're more stable, but don't allow your knees to shoot out past your toes. Push back up to the starting position and repeat.

Lunges

Strengthens the calves, quadriceps, gluteus maximus, gluteus minimus, hamstrings, adductors, abductors.

Stand in a staggered stance so one leg is about one stride in front of the other and your feet are spread slightly wider than shoulder-width. Hold a dumbbell in each hand (if you've never done this exercise before, start with 3- or 5-pound weights). Pull your shoulder blades back, and contract your abdominal muscles. Keeping the heel of your back foot on the floor, inhale and bend both knees, lowering your hips toward the floor until your front thigh is parallel with the ground. Exhale and push up to the starting position. Complete 12 to 15 repetitions, switch legs, and repeat. Work up to three sets.

Make it harder: Do backward lunges. Step backward with your right leg, taking one full stride. Bend both knees until your left thigh is parallel to the floor and your right thigh is perpendicular to it. Push yourself up to the starting position. Now step back with your left foot and repeat.

The Bridge

Strengthens the rectus abdominis.

Lie face down on the floor. Adjust your arms so they're shoulder-width apart with your elbows tucked to your sides and forearms touching the floor. Squeeze your shoulder blades together, inhale, contract your abs, and push your body up until it's parallel with the floor. You should be supporting your weight with your elbows, forearms, and toes. Your head and neck should be in line with your spine. Breathe smoothly and deeply while you try to hold this position for 60 seconds. If you can't hold it in the correct position for a full minute, finish it out on your knees instead of your toes.

Make it harder: Add alternating leg lifts. While you're in the holding pattern, lift your right leg a few inches off the floor, lower it, and then lift your right. Repeat for 60 seconds.

Good Form Guide

1. Suck It In

Tightening your abs for the duration of an exercise (imagine you’re pulling your navel back toward your spine) supports your spine and keeps you from arching or rounding your back which can lead to injury.

2. Just Breathe

Exhale deeply through the most difficult part of the move. And inhale deeply through your nose during the easier part of the move.

3. Relax

Focus on keeping your shoulders down and relaxed—not hunched up around your ears. This helps you maintain proper posture.

4. Lift and Lower on an Equal Count

It can be tempting to allow the weight to drop back to the starting position after you’ve lifted—but don’t! Lift and lower on a four-count to get max results for your effort.

5. Watch Your Toes

When doing lunges and squats, make sure that you never let your knees drift past your toes—it puts excess stress on your knees.

6. Stretch

Stretching helps keep muscles supple. Make sure you spend at least five minutes after each workout stretching your major muscles.

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