15-minute workouts: This 31-day dumbbell routine will tone and strengthen your entire body

It’s March, which means spring is officially around the corner (and beach season is coming swiftly on its heels). That’s why this month we’re focusing on strength training.

Building strength in your muscles helps build lean muscle mass, which helps burn fat. The Physical Activity Guidelines for Americans, published by the U.S. Department of Health and Human Services, recommends that adults perform muscle-strengthening activities at least two days per week. As a personal trainer, I encourage my clients to include strength training in their routine on a regular basis to accomplish two main goals: build muscle and burn fat.

This month’s workout focuses on 15-minute routines that are easy to squeeze in to a busy schedule and only requires a set of dumbbells.

Research shows that whether you decide to do all of your strength training in one day or split up the workouts into different muscle groups (i.e. leg day, arm day, etc.) your results will be similar. To make these daily workouts a quick 15 minutes, we’ve split up the body parts into three different routines:

• Upper body
• Lower body
• Core

As the month moves on, the routines progress, which you'll notice is notated by an increase in repetitions on the calendar. I recommend that you look at the workouts for the week and plan them around your schedule. If you know that you’ll be busier tomorrow than today, you may want to combine both workouts into one (i.e. perform the upper body and lower body routine on one day) so that you can just do one workout and skip it the next day.

Download your printable calendar here. Hang the calendar on your fridge, or keep it in your purse or car, for easy reference. Remember, this is just a sample of how you can structure your workouts! The calendar below is a suggested schedule, but it can be modified based on the time you have each day, so adjust your work days and rest days as needed.

Day 1: Upper Body

Day 2: Lower Body

Day 3: Core

Day 4: Rest

Day 5: Lower Body

Day 6: Rest

Day 7: Upper Body

Day 8: Rest

Day 9: Core

Day 10: Upper Body + Lower Body

Day 11: Rest

Day 12: Core

Day 13: Upper Body + Lower Body (12 reps)

Day 14: Rest

Day 15: Upper Body + Lower Body + Core (12 reps)

Day 16: Rest

Day 17: Upper Body + Lower Body at (15 reps)

Day 18: Core

Day 19: Rest

Day 20: Combo

Day 21: Rest

Day 22: Combo & Core

Day 23: Rest

Day 24: Combo + Core at (12 reps)

Day 25: Rest

Day 26: Combo + Core at (12 reps)

Day 27: Rest

Day 28: Combo + Core at (15 reps)

Day 29: Rest

Day 30: Combo + Core at (15 reps)

Day 31: Rest

I recommend starting with 5-pound dumbbells. If that feels too easy, and you can maintain proper form with heavier weights, you can go up to 7 pounds and eventually 10 pounds. I personally cap the weight at 10 pounds for my clients because they have the goal of sleeker, toned muscles. For our lower body strength training and core exercises, you’ll just need your body weight.

1. CAP Barbell Black Neoprene Dumbbells

CAP Barbell Black Neoprene Dumbbell

$14.12

$21.99

Walmart

$14.12

$19.99

Amazon

$23.05

eBay

2. CAP Barbell Coated Hex Dumbbell Weights

CAP Barbell Coated Hex Dumbbell

$27.31

$29.99

Amazon

$24.99

Walmart

$43.49

Overstock

Stand with your knees softly bent; hold onto a pair of dumbbells with one in each hand. Rest the arms down at your sides. Then, hug the elbows into the sides, shoulders back, and curl the weights up towards the shoulders into a bicep curl. Slowly lower down. Repeat 10 times.

Start standing with your feet hip-distance apart. Hinge forward at your waist and pull your abs in. Reach your torso on a diagonal so that you’re slightly bent over. Let the weights dangle down by your sides, and then hug your elbows in towards your sides and pull the weights up towards your chest. Tighten your upper back and the area in between your shoulder blades. Repeat 10 times.

To start, hold the dumbbells in a goal post position with the weights in alignment with the ears. The upper arms are parallel to the ground, and the forearms are perpendicular to the ground. Press the weights up overhead, in front of your forehead slightly so that you can see them with your eyes without tilting your head up. Then bring them back to the starting position. Repeat this 10 times.

Start with the arms down by the sides holding dumbbells. Then, exhale as you extend the arms out to the sides just as high as the shoulders. Make sure that the trapezius muscles (the muscles of the upper back/neck) are not hunching up towards your ears. Keep these muscles relaxed. Then, lower the arms back down to the starting position at your sides. Repeat this 10 times.

Stand with your feet hip-distance apart, knees slightly bent. Grab your weights in each hand, and let your arms hang down towards sides. Hinge forward at the waist so that your chest is tilted at a 45-degree angle towards the ground. Perform a row by pulling your elbows up towards the sky, hugging them into your sides. Then, holding the elbows static, bring the weights up and back towards the sky into a tricep kickback, working the upper back and back of the arms. Come back to the row position and then release the arms down. Perform this 10 times.

Stand with your feet hips-distance apart. Bend your knees and sit your glutes back, pulling your naval in towards your spine. Ensure that your knees don’t extend past your toes. Then press down through the heels to stand back up as you exhale, tightening the glutes. Repeat 10 times.

Step the right foot to the right and bend the right knee. Sink the right glute back as you keep the left leg straight. In this side lunge, hinge at the waist and be sure to engage your core! Keep the head in line with the spine and look down to the ground. Keep the shoulders relaxed. Then press down through the right heel to return back to center. Repeat 10 times, and then switch to the left side.

With your feet open hip-distance apart, step your right foot forward and bend the right knee at a 90-degree angle. Track your right knee over your right ankle. Bend the left knee down towards the ground. Then, press down through the right heel as you return back to center. Repeat 10 times with the right leg, and then 10 times with the left.

Standing upright, balance on the right foot. Extend the left leg behind you, and lean your torso forward reaching your arms towards the floor, allowing your left leg to lift up towards the ceiling behind you. Keep the leg straight and squeeze the left glute at the top. Then lower the leg back down towards the ground and bring your torso up to center. Repeat 10 times, then switch sides.

Step the feet out hips-distance apart. Bend the knees and sit back into a squat (as if you’re sitting into a chair), and then press down through the heels to come up. As you come up, lift the right leg out to the right and up as high as the hip. Keep the leg straight. Then bring the right leg back to center and go right into the squat. Repeat this 10 times with the right leg doing the leg lift after each squat, and then repeat 10 times with the left leg doing the leg lift after the squat.

Stand up with your feet hip-distance apart and hold one dumbbell in each hand. Reach your right arm towards the ceiling, and let you left hang by your side. Tilt your pelvis so that your low back is not arching and your naval is pulling in towards your spine. Then crunch the right elbow down and bring the right knee up towards the elbow. This is working the right side waist. Repeat this 10 times on the right, and then switch to the left side.

Holding one dumbbell with both hands, reach your arms up together towards the left upper corner of the room, and step your right foot out to the right. Then, pull the dumbbell down towards your right knee as you bring the right knee diagonally across the body to meet the weight in the center. Touch the hands to the right knee, and then place the right foot back down and the arms back up to the left. Repeat this 10 times, and then switch sides.

These exercises combine two moves — a leg exercise with an upper body exercise — into one exercise. They require a pair of dumbbells and allow you to get more bang for your buck time-wise. Repeat this routine three times through.

While holding one dumbbell in each hand, lower down into a squat. As you press up from the squat to standing, curl the arms up into a bicep curl. Repeat this 10 times.

Hold one dumbbell in each hand, and step to the right bending the right knee into a side lunge. Stay in the side lunge as the arms dangle down in front. From here, pull the elbows up towards your sides and pull the weights up towards your chest performing a row. Squeeze the shoulder blades together. Then, release the arms down, and press down through the right heel to press back to the center. Repeat this 10 times, and then switch to the left side.

Step forward into a forward lunge with both knees at a 90-degree angle. Holding this position, raise the dumbbells out to your sides at a 90-degree angle, creating a goal post shape with the weights in line with your ears, then press them up towards the ceiling, performing an overhead press. Bring your arms back down to your sides and press back to the starting position. Repeat this 10 times with the right leg, and then 10 times with the left leg.

Standing upright, balance on the right foot; Hold one dumbbell in each hand. Extend the left leg behind you, and lean your torso forward reaching the weights towards the floor, allowing your left leg to lift up towards the ceiling behind you. Keep the leg straight and squeeze the left glute at the top. Then lower the leg back down towards the ground and bring your torso up to center. As you come up to center, extend the arms out to the side into a side extension. Repeat this 10 times on the right and then 10 times on the left.

Hold one dumbbell in each hand and lower down into a squat with the elbows hugging in towards your sides. In the squat position, extend the arms back into a tricep extension. Release the arms as you press down through the heels to return to standing. Then, lift the right leg out to the side into a side leg lift. Return to center. Repeat this 10 times with the right leg lift and then 10 times with the left leg lift.

• Back to basics: Your one-month treadmill workout
• A one-month resistance band workout you can do anywhere
• A 30-day strength training routine — no equipment required
• A 15-minute full body HIIT workout — no equipment required
• 2-in-1 exercises that will tone your arms and abs

Want more tips like these? NBC News BETTER is obsessed with finding easier, healthier and smarter ways to live. Sign up for our newsletter and follow us on Facebook, Twitter and Instagram.