With strong legs, a solid core, and high aerobic capacity, you can do damn near anything (at least from a physical performance perspective). This  legs, core, and cardio workout was created to help soldiers survive the new Army Combat Fitness Test (ACFT), but it can also be used by civilians to survive, period.

That’s functional fitness, people.

Featured Trainer: SPC Chris Kellum is a sniper team infantryman in the Florida Army National Guard. A NETA-certified personal trainer and member of the Bravo Sierra team, his mission is to inspire others by incorporating fitness and military on his YouTube channel and documenting the process of transitioning to a warrant officer to go to flight school. All of his workouts can be found on his Playbook fitness app.

Equipment Needed: Fully equipped gym — barbell, plates, loaded sled, mini resistance bands, exercise ball, dumbbells, cables.

Time Commitment: About an hour.

Workout Overview: Kellum’s routine will increase aerobic capacity while building strength and ultimate functionality in the lower body. The main components of the workout are as follows:

Lower-body strength circuits (3) – The first one incorporates two classic lifting moves (squats and lunges); the second prescribes sled work (push and pulling) and lateral band walks; and the third hits posterior chain and calves with Romanian deadlifts, hip thrusts, and calf raises. “You’ll be lifting less weight than usual, as the intensity is high,” says Kellum. “But we still want to focus on proper form, which can be compromised by lifting heavy while depleted.”

Core isolation – Four exercises (a crunch, two rotational moves, and a plank hold) performed with short periods.

HIIT cardio sprints – Two miles total of running, broken up into two 800-meter jogs (warmup and cooldown), two 400-meter sprints, two 200-meter sprints, and four 100-meter sprints. A 1:1 work-to-rest ratio will make this portion of the workout challenging (if not downright grueling).

“This workout has been designed to create a structure to increase the combat effectiveness of our service members,” says Kellum. “The Army has released the new Army Combat Fitness Test, and to help soldiers master the events, I developed my own ‘Hybrid Warrior’ training plan. This is Part 1 of the plan to help build strength and endurance in the legs.”

Chris Kellum’s Legs, Core & Cardio Workout


  • Forward Leg Swings – 20 reps per leg
  • Lateral Leg Swings – 20 reps per leg
  • Groiners – 2 sets, 20 reps per leg
  • Sled Push – 2 sets, 20 yards (slow march, long steps, 1-2 45-pound plates)

Legs Workout

5 Exercise Athletes Sled Push
gradyreese / Getty

Circuit 1 | 4 Rounds:

    • Barbell Squat – 10-12 reps
    • Reverse Lunge – 12 reps per leg
    • Rest 45-60 seconds

Circuit 2 | 4 Rounds:

    • Sled Push & Pull – 20 yards down (push), 20 yards back (pull)
    • Lateral Band Squat Walk – 20 yards down, 20 yards back
    • Rest 45-60 seconds

Circuit 3 | 4 Rounds:

    • Romanian Deadlift – 12-15 reps
    • Glute Hip Thrust – 12-15 reps
    • Seated Dumbbell Calf Raise – 12-15 reps
    • Rest 45-60 seconds

Core Workout

Boxer working out his core muscles by doing a plank exercise in a boxing gym
G-Stock Studio

Complete all sets of each exercise before moving to the next; rest 15 seconds between sets.

  • Exercise Ball Crunch – 3 sets, 30 reps
  • Mason Twists (aka Russian Twists) – 2 sets, 40 reps
  • Side Cable Twist – 3 sets, 15 reps per side
  • Plank Hold – 1 set, max time (shoot for 2 + minutes)

HIIT Cardio Workout

Muscular man doing HIIT sprinting workouts by sprinting on a running track
Jesus Cervantes

Perform this cardio protocol after the above circuits and core workout, or in a separate session.

Directions: Alternate between sprints and rest – sprint the distance listed, then rest the amount of time it took to complete the sprint. For example, if it took you 3 minutes to run 800 meters, rest for 3 minutes then start the working sets. If it takes 90 seconds to run the first 400-meter sprint, rest 90 seconds before the next.


  • Jog 800m

Working Sets

  • 2 x 400m sprints
  • 2 x 200m sprints
  • 4 x 100m sprints

Cool down

  • Jog 800m

Exercise Notes

  • Barbell Squat – Use a weight that’s approximately 50% of your 1-rep max (1RM); for example, if your 1RM is 320, use 160 pounds for the 10- to 12-rep sets. If you don’t have a barbell (or prefer not to do the barbell version), use dumbbells, a kettlebell, or a Smith machine instead.
  • Reverse Lunge – Load with either a barbell on your back or holding dumbbells or kettlebells at your sides. Use enough weight that 12 reps is challenging.
  • Sled Push & Pull – Push the sled 20 yards fast, then pull it back slowly (walking backward) to the starting position.
  • Lateral Band Squat Walk – Perform this exercise by placing a mini-band around your thighs, just above the knees. Get into a squat position (thighs around parallel with the floor), take lateral steps in this position. Go 20 yards to one side, then 20 yards in the opposite direction. To increase difficulty, hold a plate or dumbbell out in front of you for core and shoulder activation.
  • Romanian Deadlift – This can be done with either a barbell or dumbbells.
  • Glute Hip Thrust – Perform this exercise with a barbell resting in your hip crease, sitting sideways to a bench, with your upper back on the bench.
  • Seated Dumbbell Calf Raise – If you have a seated calf raise machine available, you can use that instead of dumbbells. Otherwise, place two heavy dumbbells on top of your knees to perform the move.
  • Mason Twists – To increase difficulty (for advanced individuals), hold a medicine or weight plate over your chest with arms bent.
  • Side Cable Twist – Perform this exercise standing sideways to the weight stack, holding the cable in front of you and twisting your torso to one side. Do all reps for one side, then repeat on the other side. Don’t rest between sides. This exercise can also be done with a resistance band.
  • Plank Hold – If you repeat this workout more than once, make it your goal to increase the hold duration each time.
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