This 21-day training challenge will build serious strength in just a few weeks

This 21-day training challenge will build serious strength in just a few weeks

Don't get sucked into a workout that promises a "toned body" at the end. There's a bigger reason to exercise: it makes you feel great. “Good mental health is just as important as good physical health, and exercise is crucial to achieving both,” says trainer Jeanette Jenkins, author of The Hollywood Trainer Weight-Loss Plan: 21 Days to Make Healthy Living a Lifetime Habit. The 21-day workout challenge she created below celebrates all the good things that come with improving your fitness, including more energy, better health, and the motivation to keep coming back for more. While this routine might get you closer to your physical goals, it can also bring about invisible changes. (Related: The Anti-Running Treadmill Workout for Total Body Toning)

This 21-day workout plan is designed for all fitness levels, so just choose the exercise and cardio variations that are right for you. Are you trying to make exercise a lifelong habit? Use these three weeks as a starting point. If you're already in your own workout groove, there are plenty of challenges here to boost your results. (Related: This 30-Minute Total-Body Workout Sounds Head-to-Toe)

How it works:Jenkins' 21-day workout challenge consists of four primary workouts: three strength circuits and a cardio routine. Each circuit focuses on a different set of muscles; Do each circuit four times on the indicated days, or six times if you feel advanced. Cardio days are designed to burn calories and improve your aerobic fitness. For best results, follow the order for each day and week below.

You need:A set of light (3 to 5 pounds) dumbbells (Buy It, $15, amazon.com) and medium (8 to 10 pounds) dumbbells (Buy It, $28, amazon.com)

21 Day Training Challenge

Day 1:Cardio + stretching

Day 2:Circuits A and C

Day 3:Cardio + stretching

Day 4:Circuits B and C

Day 5:Circuit A + route

Day 6:Circuits B and C

Day 7:Rest

Repeat this same schedule for weeks two and three.

Circuit A: Chest, triceps and butt

1. Push-up/plank combination

Targets shoulders, triceps, chest, abs

AStart in a modified push-up position with your hands on the floor slightly wider than your shoulders and your knees down. Keep a straight line from the top of your head through your feet, keeping your abdominal muscles engaged.

b.Bend your elbows 90 degrees and then push them back up to start.

Repeat for 20 to 25 reps.

CAfter the last rep, lift your knees off the floor into the high plank position. Keep your stomach tense and your back straight,Hold for 30 seconds.

Enlarge:Do full push-ups; Hold plank for 60 seconds.

2. Chest fly

Targets shoulders, chest

ALie faceup on the floor with your knees bent and hold heavier dumbbells with your arms extended, palms facing each other.

b.Slowly open your arms to the sides, keeping your elbows slightly bent; Stop when the weights are about an inch above the ground.

CPush the weights back to return to the starting position.

Do 15 reps.

DImmediately grab the lighter set of weights and do it10 more reps.

Enlarge:Do 25 reps with the 8- to 10-pound weights.

3. Reverse lunge

Targets glutes, hamstrings and quads

AStand with your feet hip-width apart and hold a lighter set of dumbbells with your arms at your sides, palms facing inward.

b.Lunge with your right foot back and lower your right knee toward the floor; Bend your left knee 90 degrees, keeping it aligned over your ankle.

CReturn to start and drive body weight through your left heel; bring your right knee to hip height.

Do 15 reps. change sides; Repeat.

Enlarge:Hold heavier dumbbells and/or do 25 reps per side.

4. Squat/Chair Pose

Targets glutes, hamstrings and quads

AStand with your feet shoulder-width apart and hold lighter dumbbells on your shoulders.

b.Squat down and push your butt back. Keep your body weight over your heels.

CPush through heels to return to start, squeezing glutes.

Do 20 to 25 repetitions.

DAfter the last rep, drop the weights and bring your feet together. Squat back down, keeping knees behind toes and extending arms forward to chest level;Hold for 30 seconds.

Enlarge:Use heavier dumbbells and hold Chair Pose for 60 seconds.

Circle B: Back, biceps and thighs

1. Plié squat

Targets glutes, quads, inner thighs

AStand with your feet slightly wider than shoulder-width apart, toes turned out, and hold lighter dumbbells vertically in front of your thighs.

b.Keeping your abs tight and your upper body elevated, bend your knees to 90 degrees. Keep knees aligned between second and third toes and put weight on heels.

CTo start, press back and squeeze the glutes.

Do 15 reps.

Enlarge:Use heavier weights and/or do 25 reps.

2. Bicep curl

Targets the biceps

AStand upright with your feet together and your knees slightly bent. Hold a heavy dumbbell in each hand, palms facing up.

b.Slowly roll the weights toward your shoulders and contract your biceps.

CSlowly lower the weights to begin and repeat.

Do 15 reps.

DImmediately take the lighter weights and repeat the exercise.Do 10 more reps.

Enlarge:Do 25 reps with the heavier weights.

3. Inner/outer leg raises

Targets glutes, outer and inner thighs

AStand with your feet hip-width apart, arms extended at shoulder height, palms down.

b.Lift left leg to side, squeeze outer thigh and glutes, then lower to return to start. Next: raising and lowering.

Do 15 reps.

CWithout touching the floor, bring your left leg in front of your body and rotate your inner thigh forward. Push your left heel forward. Next: raising and lowering.

Do 15 more reps. change sides; repeat the sequence on the opposite leg.

Enlarge:Do a total of 50 reps per leg.

4. Fly back

Targets the upper back and shoulders

AStand with your feet hip-width apart, your right leg about 3 feet behind your left. Hold heavier dumbbells with your palms facing each other. Bend forward from the waist and extend your arms diagonally toward the floor just in front of your left knee.

b.Slowly open your arms straight out to your sides at shoulder height and contract your upper back muscles. Slowly lower weights and repeat.

Do 15 reps.

CImmediately take the lighter set of weights anddo 10 more reps.

Enlarge:Do 25 reps with the heavier weights.

Circuit C: Core

1. Roll up

Targets deep (transverse) and “six pack” (rectus) abdominal muscles

ALie faceup, knees bent, arms extended next to your ears, palms facing up.

b.Extend your arms straight while contracting your abdominal muscles and lift your head, neck, and shoulders off the floor. Keep your spine round and move as smoothly as possible.

CAfter you've fully rolled up, tighten your abdominal muscles and roll down one vertebra at a time.

Do 8 reps.

Enlarge:Keep your legs straight.

2. Lateral reach

Targets oblique, deep (transverse) abdominal muscles

ALie on your right side with your legs stacked, your right arm on the floor and your left arm on your left leg.

b.Keeping abs engaged, reach left hand down as if trying to touch ankle, feeling contraction in side.

CSlowly lower your back, using your obliques and abdominal muscles to provide resistance.

Do 8 reps; Switch sides and repeat.

Enlarge:Raise your legs slightly as you reach toward your ankles.

3. Boat pose

Targets deep (transverse) and “six pack” (rectus) abdominal muscles

ASit with your knees bent, feet hip-width apart. Place your hands under your thighs and breathe deeply.

b.Exhale, lift your feet off the floor (keep your knees bent), and tighten your abdominal muscles.

CLean back slightly, balance on your tailbone and open your arms wide to the sides. Hold for 8 breaths, return to start and repeat.

Do 3 reps.

Enlarge:Straighten your legs to form a 45-degree angle to the floor.

Calorie burning cardio workout

This 21-day workout challenge combines both strength and cardio for a total-body burner that will improve your fitness from the inside out. These treadmill workouts are designed to burn 300 to 500+ calories in 40 to 50 minutes, leaving you feeling optimally exhausted. Plus, they help burn fat, so all that strength training you do can manifest the toned body results you're looking for.

Choose from one of three levels (beginner, intermediate, advanced) and choose either a high-impact run or a fast, low-impact walk on an incline. Don't have access to a treadmill for your 21-day workout challenge? Perform the same program outside on flat or hilly terrain (depending on which impact level you choose). Follow your cardio workout with 5 to 10 minutes of stretching for your shoulders, chest, hips, glutes, and legs. (Related: The Ultimate Treadmill Interval Training for Every Fitness Level)

Level 1

Follow these minute-by-minute running interval workouts for a treadmill session that won't bore you to death.

• 0:00-5:00: Aufwärmen, 3,5 mph, 0 % Steigung
• 5:00-7:00: Speed-Walk, 4,0 mph, 0 % Steigung
• 7:00-9:00: Jog-Run (5,2–6,0 mph, 0 % Steigung) oder Speed-Walk (6,1 km/h, 6 % Steigung)
• 9:00-33:00: Wiederholen Sie die Minuten 5:00-9:00 sechs weitere Male, abwechselnd 2 Minuten Gehen mit 2 Minuten Laufen oder Gehen auf einer Steigung
• 33:00-38:00: Abkühlen, 3,5 mph, 0 % Steigung

Level 2

• 0:00-5:00: Aufwärmen, 3,5 mph, 0 % Steigung
• 5:00-7:00: Speed-Walk, 4,0 mph, 0 % Steigung
• 7:00-22:00: Jog-Run (5,2–6,0 mph, 0 % Steigung) oder Speed-Walk (6,1 km/h, 6 % Steigung)
• 9:00-39:00: Wiederholen Sie die Minuten von 5:00 bis 22:00 Uhr, abwechselnd 2 Minuten Gehen mit 15 Minuten Laufen oder Gehen auf einer Steigung
• 39:00-45:00: Abkühlen, 3,5 mph, 0 % Steigung

Stage 3

• 0:00-5:00: Aufwärmen, 3,5 mph, 0 % Steigung
• 5:00-10:00: Jog-Run (5,2-6-0 mph, 0 % Steigung) oder Speed-Walk (6,8 mph, 6 % Steigung)
• 10:00-12:00: Sprint (6.0-7.0 mph, 0% Steigung) oder Speed-Walk (3.8 mph, 10% Steigung)
• 12:00-47:00: Wiederholen Sie die Minuten 5:00-12:00 weitere 5 Mal, abwechselnd 5 Minuten Laufen oder Gehen auf einer Steigung
• 47:00-52:00: Abkühlen, 3,5 mph, 0 % Steigung

Adapted from The Hollywood Trainer Weight-Loss Plan by Jeanette Jenkins with permission from GPÂ Putnam’s Sons, a member of Penguin Group USA. Copyright 2007 by Jeanette Jenkins. (Training photos courtesy of Dorit Thies.)