4x4 Indoor Protocol

Norwegian HIIT method — Rhonda Patrick recommended | Feb 13, 2026

161+ bpm
Target: 4 min above 161 bpm per round
Your max HR ~169 (age 51) — this is 95% effort
RPE 8-9 out of 10. Hard but sustainable for 4 min.

Session Timeline

0:00
10 min

Warmup

Jumping jacks, bodyweight squats, arm circles, high knees (easy pace). Build from 40% to 70% effort over 10 min. Get warm, get loose.

10:00
4 min

Round 1 — GO

Pick 2-3 exercises from the menu below. Rotate every 30-45 sec. Target: HR above 161 by minute 2. Push through minutes 3-4.

14:00
3 min

Active Recovery

Walk around, light movement, controlled breathing. HR should drop to ~120-130. Don't sit down.

17:00
4 min

Round 2 — GO

Same or different exercises. HR will climb faster this round. Expect 161+ by minute 1-2.

21:00
3 min

Active Recovery

Walk, shake it out, sip water. Breathe through nose if possible.

24:00
4 min

Round 3 — GO

This is the grind round. Mind will want to quit. Stay with it. You're building VO2max.

28:00
3 min

Active Recovery

Almost there. One more. Recover enough to give round 4 everything.

31:00
4 min

Round 4 — FINISH STRONG

Last one. Leave nothing. Final 60 seconds — max effort. This is where the adaptation happens.

35:00
5 min

Cooldown

Walk, gentle stretching, controlled breathing. Let HR come down naturally. Hip flexors, hamstrings, calves.

Exercise Menu (pick 2-3 per round)

Burpees
Full burpee with jump. The king of HR elevation. 8-10 per minute pace.
HR killer
High Knees
Sprint in place, knees to hip height. Pump arms hard. Fast cadence.
HR killer
Jump Squats
Deep squat, explosive jump. Land soft. Repeat immediately. 12-15 per min.
High HR
Mountain Climbers
Plank position, drive knees to chest rapidly. Core + cardio. Fast tempo.
High HR
Shadow Boxing
Aggressive combos with footwork. Hooks, uppercuts, movement. Stay on toes.
Medium-High HR
Stair Sprints
If you have stairs — sprint up, walk down. Repeat. Fastest HR builder.
HR killer
Jumping Lunges
Alternating lunge jumps. Explosive. Builds leg power + cardio.
High HR
Tuck Jumps
Jump and pull knees to chest. Land soft, repeat. 10-12 per minute.
HR killer
Pro tip for hitting 161+: Start each round with burpees or stair sprints for the first 90 sec to spike HR fast, then maintain with high knees or mountain climbers. Watch your WHOOP live HR — once above 161, just maintain the effort.
Recovery day context: You're at 96% recovery (green) with HRV 65.8ms — this is a perfect day to push hard. Your body is primed for high strain. Go get it.
~40 min
Total session time | 16 min at high intensity | ~14-18 strain expected