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The Science Behind the Activity Score

Explore the scientific evidence behind the Sahha Activity Score, including why each activity factor matters and how research supports its contribution to health outcomes.

Physical activity is one of the strongest predictors of long-term health, longevity, and quality of life — but it cannot be captured by a single metric such as step count. Activity volume, intensity, frequency, energy expenditure, and sedentary behaviour each independently influence cardiovascular health, metabolic function, mental wellbeing, and mortality risk. The Sahha Activity Score synthesises these evidence-backed dimensions into a single interpretable measure.

The Scientific Model Behind the Activity Score

The Activity Score is based on multiple validated dimensions of physical activity behaviour:

  • Total daily movement: Steps, distance, and general locomotion throughout the day.
  • Active time and activity frequency: How often and how consistently movement occurs across the day.
  • Activity intensity: The proportion of moderate-to-vigorous physical activity (MVPA) in daily movement.
  • Energy expenditure: Active calories burned, reflecting the physiological cost of movement.
  • Sedentary behaviour and extended inactivity: Prolonged sitting or inactivity periods independent of exercise.
  • Vertical movement and load: Stair climbing and elevation gain, adding mechanical and cardiovascular demand.

Each dimension is supported by research showing its independent contribution to health, performance, and longevity.

Total Daily Movement

Why it matters Daily movement reflects overall physical activity exposure and is strongly associated with cardiovascular, metabolic, and musculoskeletal health.

What the research shows

  • Higher daily step counts are associated with lower all-cause mortality.
  • Even modest increases in daily movement reduce cardiovascular and metabolic disease risk.
  • Health benefits occur well below traditional targets such as 10,000 steps per day.

Why it’s included in the Activity Score Overall movement volume is a foundational indicator of physical activity behaviour and long-term health.

Active Time and Activity Frequency

Why it matters How often movement occurs throughout the day is as important as how much movement occurs in total.

What the research shows

  • Frequent bouts of activity improve glucose regulation and cardiovascular health.
  • Regular movement reduces cardiometabolic risk independently of total activity volume.
  • Activity spread across the day provides greater benefit than a single concentrated session.

Why it’s included in the Activity Score Consistent movement patterns support metabolic health and reduce prolonged sedentary exposure.

Activity Intensity

Why it matters Activity intensity determines the physiological stimulus placed on cardiovascular, respiratory, and musculoskeletal systems.

What the research shows

  • Moderate-to-vigorous physical activity (MVPA) is strongly associated with reduced mortality risk.
  • Higher intensity activity improves cardiorespiratory fitness more efficiently than low-intensity movement.
  • Even small amounts of vigorous activity provide disproportionate health benefits.

Why it’s included in the Activity Score Intensity reflects activity quality, not just quantity, and plays a key role in fitness and disease prevention.

Energy Expenditure (Active Calories)

Why it matters Energy expenditure reflects the physiological cost of activity and correlates with metabolic health.

What the research shows

  • Higher daily energy expenditure is associated with improved insulin sensitivity and weight regulation.
  • Active calorie burn is linked to reduced risk of metabolic syndrome and cardiovascular disease.

Why it’s included in the Activity Score Energy expenditure captures the combined effects of movement volume and intensity on the body.

Sedentary Behaviour and Extended Inactivity

Why it matters Prolonged inactivity has negative health effects independent of exercise participation.

What the research shows

  • Extended sitting time is associated with increased cardiovascular disease, diabetes, and mortality risk.
  • Sedentary behaviour negatively impacts metabolic health even among physically active individuals.
  • Breaking up sitting time improves glucose control and vascular function.

Why it’s included in the Activity Score Reducing inactivity is as important for health as increasing exercise.

Vertical Movement and Load (e.g. Floors Climbed)

Why it matters Vertical movement introduces greater mechanical and cardiovascular load than flat movement.

What the research shows

  • Stair climbing is associated with improved cardiovascular fitness and lower mortality risk.
  • Short bouts of stair climbing can meaningfully improve cardiorespiratory health.

Why it’s included in the Activity Score Vertical movement reflects activity intensity and functional strength beyond flat movement alone.

Why a Multi-Factor Activity Score Matters

No single activity metric can fully explain health outcomes. Two individuals with the same step count may experience very different health effects depending on activity intensity, sedentary time, and movement distribution. The Activity Score integrates these validated dimensions into a single interpretable measure that reflects real-world physical activity behaviour and health impact.

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