Beyond HIIT: Varied-Intensity Interval Training for Firefighters

Firefighting requires strength, power, endurance, conditioning, and movement quality to meet the physical demands of the job. So how do you train for all of it around emergency response, shift work, and interrupted sleep?

Training time is limited, and readiness can change from shift to shift. Effective training requires structure and progression while the realities of the job require adaptability.

For more than 20 years, varied-intensity interval training (VIIT) has been the most effective and efficient approach I’ve used in my own training and with the candidates, recruits, and firefighters I’ve coached.

What Is Varied-Intensity Interval Training?

Interval training alternates planned periods of work and recovery. Change the intensity, work period, or recovery, and you change the training stimulus.

Varied-intensity interval training applies that concept across different levels of intensity based on the purpose of the session. Moderate and high-intensity intervals can emphasize strength, endurance, power, and conditioning, while light and low-intensity training can support aerobic capacity, movement quality, mobility, flexibility, and recovery.

Varied doesn’t mean random. Each session is part of a structured and progressive training plan.

The Competition That Changed My Approach to Firefighter Fitness

My introduction to this style of training happened unexpectedly in 2005, when Scott Sonnon walked into Station One and told me the police department had challenged us to a tactical fitness competition. We later learned he had told the police that we had challenged them.

So many people wanted to participate that both departments held qualifiers to determine who would compete. The fire department won, and our prize was a year of weekly tactical fitness training with Coach Sonnon.

At the time, I was a Peer Fitness Trainer conducting department fitness assessments twice a year. Most participants already had strong training backgrounds, yet I saw improvements in aerobic capacity, body composition, strength, muscular endurance, and movement quality.

We continued applying these principles, including a 108-day fitness and nutrition challenge in 2011. Among consistent participants, average improvements included a 1.73 ml/kg/min increase in VO₂ max, four additional pull-ups, and 1.2 inches off the waist.

I’ve continued to apply and refine the methodology with candidates, recruits, incumbent firefighters, and in my own training.

Applying VIIT to Firefighter Tactical Fitness

When firefighters hear interval training, they often think of high-intensity interval training. Hard circuits. Short rest periods. Deck-of-cards workouts. Keep moving until the clock stops.

HIIT has a place in firefighter fitness, but high intensity is only one way to use interval training. Changing the interval structure, resistance, volume, movement speed, recovery, and effort can shift the training emphasis.

Longer intervals with moderate resistance can emphasize muscular and aerobic endurance. Increasing resistance and recovery while reducing repetitions can shift the emphasis toward strength. Shorter, higher-output efforts can emphasize power and anaerobic capacity. Light and low-intensity sessions build the aerobic base and movement quality that support recovery between harder sessions.

Firefighter Tactical Fitness applies these principles to job-specific physical preparation for occupational training and emergency response. VIIT provides one way to organize that training.

Interval training isn’t limited to treadmills, bikes, rowers, and other cardio equipment. Interval protocols can also be used to load fundamental movement patterns like the squat, hinge, lunge, push, pull, rotation, and locomotion. Kettlebells, sandbags, medicine balls, steel clubs, suspension trainers, and other simple tools make it possible to combine strength and conditioning efficiently within the same workout.

Many sessions can be completed in 45 minutes or less, with approximately 20 minutes of interval work during moderate- and high-intensity training. That’s roughly the sustained work a firefighter may do on one air bottle, without trying to recreate a fireground operation.

Managing intensity takes practice. Feedback from performance, effort, and movement quality can help you recognize when you’re drifting away from the purpose of the session and adjust load, volume, tempo, or recovery. Like a race car driver entering a turn, you back off enough to stay in control, then accelerate when you’re ready.

Structured, Progressive, and Adaptable

I often ask firefighters, “Are you training or just working out?” because hard work and intentional training are not the same thing. Individual sessions should work together as part of a larger training plan, but firefighting doesn’t happen under controlled conditions. Calls, interrupted sleep, occupational stress, and accumulated fatigue can change readiness from one day to the next.

A hard workout after a quiet shift isn’t the same as that workout after a working fire and a night of interrupted sleep. The workout on the calendar hasn’t changed, but the firefighter has. A good training plan accounts for predictable demands while leaving room to adjust when conditions change.

For an operations firefighter working a 24/48–24/96 schedule, that might look like this:

• Day 1 — On Shift: Active Recovery + Mobility + Occupational Training
• Day 2 — Off Shift: Aerobic Training + Flexibility
• Day 3 — Off Shift: Strength Training A
• Day 4 — On Shift: Active Recovery + Mobility + Occupational Training
• Day 5 — Off Shift: Aerobic Training + Flexibility
• Day 6 — Off Shift: Strength Training B
• Day 7 — Off Shift: Active Recovery + Mobility
• Day 8 — Off Shift: Metabolic Conditioning

The harder sessions are intentionally placed off shift, while light and low-intensity sessions support training and recovery around occupational demands. If emergency response, interrupted sleep, overtime, or other demands change readiness, the individual session can be adjusted without abandoning the larger plan.

The specific training cycle will look different throughout a firefighter’s career. Candidates and recruits might use a seven-day cycle organized around physical ability testing or academy training. Firefighters working an administrative schedule may also train within a traditional seven-day week, while operations firefighters can organize training around their shift cycle. So how do you train for the physical demands of firefighting around the realities of the job? Varied-intensity interval training provides a way to develop multiple physical capacities within a structured, progressive plan that can adapt when conditions change. Prepare for the demands of the job and remain response ready throughout your career.