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Feeling a little soft in the middle? You're not alone. Plenty of people struggle with their stomachs after the holidays — but that doesn't mean you're stuck with that gut forever.

Personal trainer Ali Gritz has one of the tightest cores in New York, so we asked if she'd demonstrate her top tummy-toning exercises during a recent visit to her "Absolution" class at Crunch Fitness. Without the use of weights or machines, Gritz gave us three great moves (along with more advanced variations of each) for strengening our abdominals and obliques.

Follow along with Ali in the video above as she explains her Absolution exercises, or keep reading for a detailed description.

Leg Extensions:

  • Start on the floor in a crunch position, with your hands behind your head, your knees bent, and your feet on the ground.
  • Begin by lifting your right knee toward your face, keeping your leg bent. Bring it back down in a controlled motion and touch your heel to the ground.
  • Lift your left knee in the same fashion as the right, then bring it down in a controlled motion and touch your heel to the ground. Try to perform these motions simultaneously; as one leg goes up, the other should be coming down.
  • Alternate for 15–20 reps, making sure to maintain tension in your abdominal muscles.
  • For a more advanced workout, lift both knees simultaneously, exhaling as you come up, and then bring them both down in a controlled motion.

Planks:

  • Start in plank position, with only your forearms and feet touching the ground.
  • Press your feet into the floor and lower (or raise) your hips until your body is aligned, and squeeze your glutes until you feel a burn.
  • For a more challenging exercise, try lifting one foot off the ground (about 6–12 inches) during your plank, then bring it back down to the floor and repeat with the other leg. Perform about 15 repetitions before resting.

Side Planks:

  • Lying on your right side, press your right forearm into the ground to lift your torso. Fully extend your right leg, then bring your left foot over the right leg and place your left foot on the gound in front of you.
  • Push into your feet to gently lift your hips from the ground, so your body is aligned and only your feet and forearm are touching the floor, keeping tension in your abs the whole time. Hold until you feel a burn, then rest. Repeat on your left side.
  • For a more advanced workout, stack your left left atop your right and hold; experts can try bringing their left foot forward, tapping it to the ground, then bringing the same foot behind the right leg, again tapping it to the ground, and repeating. Perform 15 reps, then repeat the side plank on your left side.