Hard truth: you can't expect to do the same workout over and over and continue seeing results. Instead, you have to establish a base level of fitness and then build on the moves as you get stronger. That's exactly how Le Sweat [1] founder Charlee Atkins, CSCS, designed POPSUGAR's 4-Week Workout Challenge. Coming off the first two weeks of the plan, this upper body and core workout should feel challenging, with the goal of taking your strength training to the next level.

That said, these moves shouldn't feel impossible — so, if you find that you're struggling, scale back down and continue building that baseline strength. You'll get there in time.

20-Minute, No-Equipment Upper Body and Core Workout

Directions: Complete each exercise for 40 seconds, followed by a 10-second recovery. You'll do three rounds total with a one-minute rest in between rounds. Before you start, warm up with this seven-minute dynamic routine [2], and cool down postcircuit with these foam-rolling exercises [3] that will help restore your muscles.

Exercises:

• Plank walk
• Leg lowers
• Bear plank knee taps
• Push-up reach
• Single-leg hip raises
• Plank reach

Plank Walk

• Begin in a high plank position with your hands slightly wider than shoulder-width apart.
• Lower your right elbow to the mat, then your left, coming into an elbow plank.
• Put your right hand on the mat, and straighten your right elbow. Do the same on the left to return to a full plank.
• Continue this movement for 40 seconds, making sure to alternate your leading arm.

Leg Lowers

• Lie on your back with your legs straight up, perpendicular to the floor.
• Bring your elbows out to your sides and your arms to your chest, making a fist with each hand.
• Keeping your foot flat and your core engaged, slowly lower your left leg toward the mat, pausing a few inches before your heel would touch the floor. Make sure your lower back stays anchored to the mat.
• Press your elbows into the mat and squeeze your core as you raise the leg back to starting position.
• Repeat with your right leg, and continue alternating sides for 40 seconds.

Bear Plank Knee Tap

• Begin on all fours with your hands directly below your shoulders and your knees beneath your hips. Keeping your core engaged and your back flat, lift your knees so they're hovering over the mat.
• Bring your right hand back to tap your left knee, lifting your foot off the ground to allow the two to meet. Return your hand and foot to the mat, then alternate, tapping your left hand to your right knee.
• Continue alternating hands and knees for 40 seconds.

Push-Up Reach

• Lie face down on the floor with your toes tucked into the mat and your arms stretched out overhead.
• Take a breath in, and as you exhale, bring your arms back so your hands are planted directly below your shoulders, and push your body up into a high plank position. Draw your belly button into your spine to help maintain a straight line from head to toe.
• Inhale and slowly lower back down to starting position.
• Continue this push-up and reach sequence for 40 seconds.

Single-Leg Hip Raise

• Lie on your back, and place your hands on the floor for stability. Bend your knees and lift your left leg up toward the ceiling, keeping your knee at a 90-degree angle.
• Press your right heel into the floor, and lift your pelvis up into a bridge position.
• Slowly lower your body to the floor, making sure to tap your butt on the mat before raising up again. Repeat with the same leg for the full 40 seconds.
• Once the 40 seconds is up, rest and complete the move with your left foot planted on the ground.

Plank Reach

• Begin in an elbow plank with your feet slightly wider than your hips for added stability.
• Reach your left arm straight out, tapping your fingers to the floor in front of you. Bring your arm back to the mat, then reach forward with your right arm.
• Continue alternating arms for 40 seconds.