## Definitions

### Power
In the context of cycling and exercise physiology, **power** refers to the rate at which work is done or energy is transferred. It is usually measured in watts (W) and represents the output of physical effort. For cyclists, power can be measured using power meters that track the force applied to the pedals and the speed of the bike.

### Average Power
**Average power** is the mean power output over a given period. It provides a simple way to assess the overall effort during a ride or workout. For example, if a cyclist rides for one hour and generates varying power outputs throughout, the average power would be the total energy expended divided by the time.

### Normalized Power
**Normalized Power (NP)** is a metric that accounts for the variability in power output during a ride. It provides a more accurate reflection of the physiological demands than average power by considering the fluctuations and the higher cost of more intense efforts. NP is calculated using a specific algorithm that emphasizes the power variability and its impact on the body.

### Functional Threshold Power (FTP)
**Functional Threshold Power (FTP)** is the highest power a cyclist can sustain for one hour without fatigue. It is a critical metric for training and racing, as it helps in setting training zones and gauging performance. FTP is often determined through testing protocols that estimate the one-hour power from shorter, more intense efforts.

### Intensity Factor (IF)
**Intensity Factor (IF)** is a measure of the intensity of a workout relative to the athlete's FTP. It is calculated as the ratio of normalized power to FTP. An IF of 1.0 means the workout was done at the athlete's threshold power, while values above or below indicate higher or lower intensity, respectively.

### Training Stress Score (TSS)
**Training Stress Score (TSS)** quantifies the training load of a workout. It considers the intensity (via IF) and duration to provide a single score that reflects the overall stress imposed on the body. TSS helps in balancing training loads and recovery, guiding athletes in managing their training programs effectively.

### Acute Training Load (ATL)
**Acute Training Load (ATL)** represents the short-term training load, typically over the last 7 days. It reflects the recent training stress and is used to monitor the immediate fatigue and readiness of an athlete.

### Chronic Training Load (CTL)
**Chronic Training Load (CTL)** indicates the long-term training load, usually averaged over 42 days. It provides insight into an athlete's fitness level based on the accumulated training stress over time. A higher CTL suggests greater fitness but also requires careful management to avoid overtraining.

### Metabolic Equivalents (METs)
**Metabolic Equivalents (METs)** are a unit used to estimate the amount of energy expenditure during physical activities. One MET is defined as the energy cost of sitting quietly, roughly equivalent to 3.5 mL of oxygen per kilogram of body weight per minute. Activities are rated in multiples of METs, with higher values indicating more intense exercise.

- **Light intensity**: < 3 METs (e.g., walking slowly)
- **Moderate intensity**: 3-6 METs (e.g., brisk walking)
- **Vigorous intensity**: > 6 METs (e.g., running)

### Moderate Physical Activity (MPA)
**Moderate Physical Activity (MPA)** refers to activities that require a moderate amount of effort and noticeably accelerate the heart rate. Examples include brisk walking, recreational swimming, or cycling at a moderate pace. MPA is generally classified as activities that require 3 to 6 METs.

### Vigorous Physical Activity (VPA)
**Vigorous Physical Activity (VPA)** involves activities that demand a high level of effort and result in rapid breathing and a significant increase in heart rate. Examples include running, fast cycling, or competitive sports. VPA typically involves activities that require more than 6 METs.

These metrics and concepts are essential for structuring training programs, assessing performance, and ensuring balanced progress for athletes.

## [Long-Term Leisure-Time Physical Activity Intensity and All-Cause and Cause-Specific Mortality: A Prospective Cohort of US Adults](https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.121.058162)

> The nearly maximum association with lower mortality was achieved by performing:
> - ≈150 to 300 min/wk of long-term leisure-time VPA,
> - 300 to 600 min/wk of long-term leisure-time MPA, or
> - an equivalent combination of both.

## Aligning Cycling Metrics to Physical Activity

### Understanding the Recommendations

The study recommends:
- 150 to 300 minutes per week of vigorous physical activity (VPA)
- 300 to 600 minutes per week of moderate physical activity (MPA)
- An equivalent combination of both

### Mapping Cycling Metrics to Activity Intensity

1. **Intensity Factor (IF)**:
- IF gives you a measure of how intense your workout is relative to your Functional Threshold Power (FTP).
- Typically, an IF of:
- **0.85 - 1.0** indicates vigorous activity (VPA)
- **0.55 - 0.75** indicates moderate activity (MPA)

2. **Training Stress Score (TSS)**:
- TSS incorporates both intensity and duration to give you a single value representing the training load.
- You can track your weekly TSS and correlate it with the recommended exercise duration and intensity.

### Calculating the Weekly Targets

1. **Determine Your VPA and MPA Minutes**:
- For VPA: Sum the minutes of your rides where IF is between 0.85 and 1.0.
- For MPA: Sum the minutes of your rides where IF is between 0.55 and 0.75.

2. **Equivalent Combination**:
- You can mix both VPA and MPA to achieve the target. For calculation:
- 1 minute of VPA ≈ 2 minutes of MPA.

### Example Calculation

Assume you have the following weekly cycling data:

- **Ride 1**: 60 minutes, IF = 0.90 (VPA)
- **Ride 2**: 90 minutes, IF = 0.70 (MPA)
- **Ride 3**: 120 minutes, IF = 0.60 (MPA)
- **Ride 4**: 45 minutes, IF = 0.85 (VPA)

#### Step-by-Step:

1. **Calculate VPA Minutes:**
- Ride 1: 60 minutes
- Ride 4: 45 minutes
- **Total VPA**: 60 + 45 = 105 minutes

2. **Calculate MPA Minutes:**
- Ride 2: 90 minutes
- Ride 3: 120 minutes
- **Total MPA**: 90 + 120 = 210 minutes

3. **Convert VPA to MPA Equivalent**:
- 105 minutes of VPA is equivalent to 210 minutes of MPA (since 1 minute of VPA ≈ 2 minutes of MPA).

4. **Total Equivalent MPA**:
- 210 minutes (MPA) + 210 minutes (VPA converted to MPA) = 420 minutes

This total of 420 minutes is within the recommended range of 300 to 600 minutes of MPA equivalent per week.

### Using TSS for Monitoring

While TSS does not directly translate to VPA or MPA minutes, it can be used to monitor overall training load:

- Track your weekly TSS to ensure you are within a sustainable training load.
- Compare your weekly TSS over time to see if you are consistently hitting your targets without overtraining.

### Practical Tips

- **Use Training Software**: Tools like TrainingPeaks, Strava, or Garmin Connect can help track and analyze your IF, TSS, and total workout time.
- **Regular Testing**: Ensure your FTP is up-to-date for accurate IF calculations.
- **Balance and Recovery**: Ensure you have a balanced training plan that includes rest and recovery to avoid overtraining.

By monitoring these metrics and converting your workout data to match the study's recommendations, you can ensure you are meeting the targets for reducing mortality risk through physical activity.

## [Activity Intensity During Free-Living Activities in Children and Adolescents With Inherited Arrhythmia Syndromes](https://www.ahajournals.org/doi/10.1161/circep.113.000514)

> - moderate (4–7 METs)
> - vigorous (≥7 METs)
> - very vigorous (≥10 METs)