Training Density
Also known as: Work Density, Work Rate, Workload Density
How much work you fit into a unit of time. Density combines volume (or tonnage) with session duration into a single "work per minute" number — useful for comparing a fast circuit-style session to a slow heavy strength day, and for spotting when rest periods are drifting longer.
Formula
Density = total work / session duration
Volume density = total reps / minutes
Tonnage density = total tonnage (kg) / minutesExample
Session A: 4,000 kg tonnage in 60 minutes → tonnage density 66.7 kg/min. Session B: 4,000 kg tonnage in 45 minutes → 88.9 kg/min. Same total work; Session B is one-third denser.
How Afitpilot Uses This
Density is a derived view of metrics we already track. Volume density and tonnage density are computed from logged session duration alongside the existing volume and tonnage numbers — no extra logging required. We expose density as a secondary metric: useful for athletes whose goal is conditioning or hypertrophy under fatigue, less meaningful for max-strength sessions where long rests are intentional.
Typical training density by style
| Who / Context | Value | Note |
|---|---|---|
| Powerlifting (heavy block) | 40-80 kg/min | Long rest periods (3-5 min) lower density on purpose |
| Hypertrophy / bodybuilding | 100-180 kg/min | Shorter rest (60-120 s); density is part of the stimulus |
| CrossFit / circuit | 200-400+ kg/min | Minimal rest; density is the headline metric |
| Regular gym goer | 80-140 kg/min | Wide variance — rest discipline matters more than load |
| Active aging (60+) | 30-70 kg/min | Generous rest is appropriate; chasing density adds joint risk for little upside |
Known Limitations
- •Density rewards short rest periods, which is the right move for hypertrophy and conditioning blocks but the wrong move for a max-strength block where 3-5 minute rests are prescribed for a reason. Reading density without context invites athletes to rush sets they shouldn't rush.
- •Session duration depends on accurate start/end timestamps. If an athlete logs late or forgets to close the session, the denominator gets noisy and density numbers swing wildly.
- •Density doesn't distinguish productive work time from setup, warm-up, or socialising at the gym. Two athletes with identical tonnage and identical clock time can have very different actual work-to-rest ratios.
- •Comparing density across modalities is misleading. 100 kg/min on a strength day means something different than 100 kg/min on a circuit day — the underlying physiology isn't the same.
Science Context
Density (often called "work density" or "work rate") sits between pure volume and pure intensity as a training variable. It has a long history in conditioning literature — most notably Vladimir Issurin's block periodisation framework, where density blocks are explicitly programmed to drive conditioning adaptation. Recent hypertrophy research (Schoenfeld 2017) suggests shorter rest periods (and thus higher density) do not impair growth when total volume is matched, but can compress a session into less clock time — a meaningful practical benefit for self-coached athletes.