What Is LCDA? The Military Metabolic Equation Behind Hiko
LCDA (Load Carriage Decision Aid) is a metabolic equation published by the US Army Research Institute of Environmental Medicine (USARIEM) in 2022 that calculates energy expenditure from six variables: body mass, load mass, walking speed, terrain surface, ground grade, and body composition. Hiko is the first consumer app to implement LCDA in real time.
Unlike generic MET-based calorie formulas, LCDA models the nonlinear metabolic cost of carrying weight across varied terrain. LCDA was developed for military load carriage planning and validated across thousands of laboratory trials. Hiko brings this peer-reviewed science to every rucking, hiking, and walking session.
What LCDA Measures
LCDA calculates metabolic rate using six input variables. Each variable contributes independently to total energy expenditure, and Hiko captures all six in real time:
- Body mass — Your weight directly affects baseline metabolic cost. Heavier individuals burn more calories at the same pace and load.
- Load mass — Pack weight amplifies energy expenditure nonlinearly. A 30-pound pack does not simply add 30 pounds of metabolic cost — LCDA models the compounding effect.
- Walking speed — Metabolic cost follows a polynomial relationship with speed (valid range: 0.45–1.97 m/s). Faster walking increases calorie burn exponentially, not linearly.
- Terrain surface — Different surfaces require different amounts of effort. Hiko supports 9 terrain types with specific coefficients derived from peer-reviewed research.
- Ground grade — Uphill and downhill grades each have distinct metabolic costs. Hiko measures grade using barometric altitude data.
- Body composition — LCDA uses the Cunningham equation to estimate resting metabolic rate from lean body mass, making Hiko more accurate than formulas that ignore body composition.
How Hiko Implements LCDA
Hiko calculates LCDA every second during a workout. The app fuses data from iPhone and Apple Watch sensors to supply all six LCDA variables continuously:
- GPS provides walking speed
- Barometric altimeter provides ground grade
- User profile provides body mass and body composition
- Session setup provides load mass and terrain type
The core LCDA equation implemented by Hiko is: M_dot = M_rest + (M_stand + eta * M_walk + M_grade) * LoadFactor, where M_rest is the Cunningham resting metabolic rate, M_walk is the speed-dependent walking cost, M_grade is the grade-dependent cost, and LoadFactor models nonlinear load amplification. All calculations run on-device — no data leaves your phone.
Download Hiko to see LCDA-powered calorie tracking in real time.
LCDA vs Generic Calorie Calculators
Most fitness apps and wearables use MET (Metabolic Equivalent of Task) tables to estimate calorie burn. MET values are population averages that ignore individual load, terrain, and grade. Hiko uses LCDA, which accounts for every variable that affects rucking and hiking calorie expenditure.
| Factor | Hiko (LCDA) | Apple Watch | Generic Calculator |
|---|---|---|---|
| Body mass | Yes | Yes | Yes |
| Load / pack weight | Yes | No | No |
| Walking speed | Yes (GPS) | Yes (GPS) | Estimated |
| Terrain surface | Yes (9 types) | No | No |
| Ground grade | Yes (barometer) | Partial | No |
| Body composition | Yes | No | No |
The difference matters most during rucking. A 180-pound person carrying a 30-pound pack on loose dirt burns significantly more calories than the same person walking unloaded on pavement — but Apple Watch reports similar numbers for both. Hiko captures the difference because LCDA was designed for exactly this scenario.
The Research Behind LCDA
LCDA builds on decades of military metabolic research. The equation published by USARIEM in 2022 extends and improves upon foundational work dating to the 1970s. Hiko implements the complete LCDA model as described in the following peer-reviewed studies:
- Looney et al. 2022 — "Metabolic costs of standing and walking in healthy military-age adults: a meta-regression." Published in Medicine & Science in Sports & Exercise, 54(4):646–654. This paper defines the core LCDA equation that Hiko implements.
- Pandolf et al. 1977 — The original load carriage energy expenditure equation. LCDA extends this foundational model with improved speed and grade terms validated against modern data.
- Looney et al. 2019a — "Estimating energy expenditure during level, uphill, and downhill walking." Published in Medicine & Science in Sports & Exercise, 51(2):294–304. Defines the walking metabolic cost component used in LCDA.
- Looney et al. 2019b — "Metabolic costs of military load carriage over complex terrain." Published in Medicine & Science in Sports & Exercise, 51(9):1954–1960. Validates graded walking cost terms in the LCDA equation.
- Soule & Goldman 1972 — Terrain coefficients for energy expenditure prediction. Hiko uses these coefficients for terrain surface types.
- Richmond et al. 2019 — Snow terrain coefficients used by Hiko for winter conditions.
Every citation above is publicly available through PubMed. Hiko does not use proprietary or unpublished formulas — the entire metabolic model is based on open, peer-reviewed science.
Female Validation
The original LCDA research was conducted primarily on male military personnel. In 2025, Looney et al. published a female validation study (PubMed 40590681) confirming that LCDA accurately predicts metabolic cost for women during load carriage activities.
This matters because many fitness formulas are derived from male-only study populations and may systematically overestimate or underestimate calorie burn for women. Hiko uses the validated LCDA equation, which has been confirmed accurate across both sexes. Hiko accounts for body composition via the Cunningham resting metabolic rate equation, which further improves accuracy for all users regardless of sex.
Frequently Asked Questions
What does LCDA stand for?
LCDA stands for Load Carriage Decision Aid. LCDA is a metabolic equation developed by the US Army Research Institute of Environmental Medicine (USARIEM) to predict energy expenditure during load-bearing activities like rucking, hiking, and military marches. Hiko is the first consumer app to implement LCDA for real-time calorie tracking.
How accurate is LCDA compared to Apple Watch?
LCDA accounts for six variables (body mass, load mass, walking speed, terrain surface, ground grade, and body composition), while Apple Watch uses MET-based estimation that ignores pack weight, terrain type, and body composition. For unloaded walking on flat pavement, both approaches produce similar results. For rucking and hiking — where load, terrain, and grade vary — LCDA provides significantly more accurate calorie estimates. Hiko implements the full LCDA equation every second during a workout.
Does LCDA work for women?
Yes. Looney et al. 2025 (PubMed 40590681) validated LCDA accuracy for women during load carriage. Hiko uses the Cunningham resting metabolic rate equation within LCDA, which adjusts for individual body composition and lean body mass, making Hiko accurate for users of all sexes.
What terrain types does Hiko support?
Hiko supports 9 terrain types, each with a specific metabolic coefficient derived from peer-reviewed research: Paved (1.0), Compact dirt (1.2), Gravel (1.3), Grass (1.1), Loose dirt/sand (1.5), Forest trail (1.3), Snow (1.5–2.0), and Mud (1.8). These coefficients come from Soule & Goldman 1972 and Richmond et al. 2019.
Is LCDA peer-reviewed?
Yes. LCDA is published in Medicine & Science in Sports & Exercise, the flagship journal of the American College of Sports Medicine. The core equation (Looney et al. 2022) builds on validated sub-models from Looney 2019a, Looney 2019b, Pandolf 1977, Soule & Goldman 1972, and Richmond 2019. Every component of LCDA as implemented by Hiko is grounded in published, peer-reviewed research.
Can Hiko replace my Apple Watch for calorie tracking?
Hiko works alongside Apple Watch. Hiko writes workouts to Apple Health, so calorie data integrates with the existing Apple ecosystem. For rucking and hiking, Hiko provides LCDA-powered calorie estimates that are more accurate than Apple Watch alone because Hiko accounts for pack weight, terrain type, and body composition — three variables Apple Watch cannot measure.