Cardio

Training load: how to balance lifting and cardio

Lifting and cardio stress your body in different ways, so folding them into one number hides more than it shows. Fortior scores each workout twice, once for cardio and once for lifting, and keeps both on the same 0 to 100 scale.

Updated October 24, 2026

What training load means

Training load is a number for how much work a session or a week contained. Tools usually count either what you did (kilograms lifted, kilometres covered) or how your body responded (heart rate, how hard it felt). It lets you compare a long easy run with a short heavy lift.

The catch is that lifting and cardio load different systems. A hard leg session and a long run both tire you, but they tire different things and recover on different timelines. That is why Fortior keeps two scores apart instead of adding them.

Two scores on one scale

Every completed workout and cardio activity gets up to two scores out of 100:

• Cardio Load Score comes from your heart rate during the session. Time at higher heart rates counts for more, using a heart-rate-based training impulse. With too few readings Fortior uses your average heart rate, and with none it uses how hard the session felt (1 to 10) times its minutes. It relies on your resting and maximum heart rate, which Fortior estimates from your own data much as it does for your heart rate zones.
• Muscular Load Score comes from the working sets you complete: how many reps, how heavy they were against your estimated max for that lift, how close to failure they were, and how much of the body the lift works. It blends total work with the most-worked muscle. Warm-up and skipped sets don't count, and a blank reps-in-reserve field counts as two.

Why scores rise more slowly near the top

Both scores use the same shape of curve. Divide a session's load by a reference amount to get x, and the score follows:

Doubling a session doesn't double its score, so a huge day still lands below 100. The Muscular Load Score uses the same shape on a scale that starts at 1.

Each score also gets a band: 1 to 20 Very light, 21 to 40 Light, 41 to 60 Moderate, 61 to 80 High, 81 to 90 Very high, and 91 to 100 Extreme. Bands describe the score. They are not a verdict on the workout.

A worked example

Say your resting heart rate is 55 bpm, your maximum is 190 bpm, and you run for 45 minutes at a steady 150 bpm. That is (150 − 55) ÷ (190 − 55) = 70% of your heart rate reserve. Weighting time at that intensity gives a training impulse of about 78, which is 0.87 of Fortior's cardio reference of 90. The score is 100 × (1 − e^(−0.87)) = 58, in the Moderate band.

Fortior uses slightly different published weightings depending on the sex in your profile, so another profile can see a few points more or less for the same run (62 with the other standard set).

Now suppose you do two such runs in one day. Fortior adds their loads before scaling: 0.87 + 0.87 = 1.74, so the day scores 82, not 58 + 58 = 116.

Seeing both in one view

In Progress, the Overview shows a Training load section with two daily charts for the last 28 days, one for each score, with the latest score and band above each chart. Once you have eight earlier tracked days, each chart also says how the latest day compares with them. Each day's score totals that day's sessions and scales them once, and the two scores are never added together.

Open any completed workout or cardio activity to see its own pair of scores. Tap one to see what it was worked out from and how sure Fortior is.

Acute versus chronic load

Coaches often compare short-term load (acute, usually the last week) with longer-term load (chronic, usually the last four weeks). A sudden jump above your usual is worth noticing, and a gradual build is what most plans aim for.

Fortior shows this on Today. The Strength card tracks two running totals of your recent training: fitness, which builds slowly and fades over weeks, and fatigue, which builds quickly and fades over days. Form is the gap between them. A one-word label compares today's form with your own recent range: Fresh, Primed, Balanced, Fatigued or Run down. It reads Building until you have logged about seven workouts. The Strength card also counts cardio you have logged, converted onto the same scale, so a hard week of running shows up there. If you have logged cardio lately, the Cardio card gives the same kind of label for your cardio alone.

Under the Strength label, Training-load ratio is the acute-to-chronic ratio: your average daily load over the last 7 days divided by your average over the last 28. If the last 7 days average 36 units a day and the last 28 average 30, the ratio is 36 ÷ 30 = 1.20. A ratio near 1.0 means this week looks like your recent norm. Fortior adds a note when it climbs above 1.5 (ramping fast) or falls below 0.8 (tapering).

These figures are estimated from your logs. Treat them as prompts to look at your week, not as safety limits.

How to balance lifting and cardio

No tool can tell you the right mix for your goal, but many coaches check these things:

• Read both scores. A high Muscular Load Score with a near-empty Cardio Load Score is a lifting-only stretch, and the reverse is cardio-only. Neither is wrong, but it helps to see which one you are in.
• Watch the timing. When you tap Recompute in Progress, Fortior looks for a hard cardio session within a few hours before a lift, or within a day after one, and shows what it finds as a Training Nudge on Today. It is an observation, not a rule.
• Check your easy-to-hard mix. Intensity Distribution in the Cardio category shows how your cardio time splits across zones.

What the scores are not

Neither score is readiness, recovery, calories, injury risk or a grade for the workout, and neither tells you what to do next. Don't compare them directly with WHOOP Strain or Strava Relative Effort, which use their own scales. Fortior shows those figures as the provider reported them.

Training load scores are estimates based on your logged workouts and heart rate. They are not medical measurements, and Fortior is not medical advice.