# Power-Based Race Execution · Triathlon Level 8: Expert

Triathlon · Level 8: Expert · Insporta Book (https://book.insporta.app/triathlon/level-8/power-based-race-execution/)

Power-Based Race Execution in Triathlon (Level 8: Expert) on Insporta: 100 sourced facts behind 10 tests. Covers: how normalised power and tss are cal.

Racing with power at expert level: how normalised power and TSS are calculated, race targets by distance, critical power and W prime, W prime balance and surges, durability and the power-duration curve, pacing terrain, the evidence on pacing, power meter accuracy, conditions and positions, and planning the bike for the run.

## Test 1: How Normalised Power and TSS Are Calculated

- Coggan's algorithm smooths power with a 30-second rolling average before weighting it. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Raising to the fourth power emphasises hard efforts, reflecting their disproportionate physiological cost. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Many physiological responses, such as oxygen uptake, adjust with a half-life of around 30 seconds. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Averaging values raised to the fourth power can only equal or exceed the plain average. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- The algorithm was designed for efforts of roughly 20 minutes or more. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- IF expresses how hard a ride was relative to threshold. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- TSS is scaled so that one hour at IF 1.0 equals 100. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- TSS = hours x IF squared x 100 = 2 x 0.64 x 100 = 128. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- TSS scales with IF squared but only linearly with time. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- 5 x 0.72 squared x 100 = 5 x 0.518 x 100 = about 259. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))

## Test 2: Race Targets by Distance

- Coaching guidance places full-distance bike legs at roughly 68-78% of FTP, an intensity factor of 0.68-0.78, depending on ability. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Half-distance bike legs typically sit around 80-85% of FTP. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Around an hour of riding allows a higher share of threshold, while still leaving a run to come. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Fatigue and fuel limits reduce the fraction of FTP that can be held as duration grows. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- A VI near 1.0 means steady power; larger values signal surges that cost energy for the run. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Bike TSS well above about 300 is often associated with a poor marathon, though it varies with fitness. (Source: Friel, The Power Meter Handbook (2012))
- 0.72 x 250 = 180 W. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Two athletes with the same FTP can differ greatly in how much power they keep after several hours. (Source: Maunder et al., Sports Med 2021)
- Freewheeling downhill lowers average power, while normalised power accounts for the harder climbing. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- The same normalised power ridden unevenly means more hard efforts, which cost more for the run. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))

## Test 3: Critical Power and W Prime

- CP is the power that could in theory be sustained for a long time without exhausting W prime. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Monod and Scherrer proposed the hyperbolic relationship between power and time to exhaustion. (Source: Monod & Scherrer, Ergonomics 1965)
- W prime is a finite energy reserve, in kilojoules, that is used whenever power exceeds CP. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Typical values range from around 10 to 25 kJ. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Time = W prime / (P - CP) = 20,000 / 100 = 200 s. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Above CP, oxygen uptake and lactate keep rising to maximum; below it, a steady state is possible. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Both sit near the boundary of sustainable effort, but CP comes from a model and FTP from a field test. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Maximal efforts of roughly 3 to 20 minutes are fitted to the power-duration model. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Any power above CP uses W prime; at a small margin it simply lasts longer before exhaustion. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Below CP, W prime is not being used and is reconstituted over time. (Source: Skiba et al., Med Sci Sports Exerc 2012)

## Test 4: W Prime Balance and Surges

- It subtracts work done above CP and adds back recovery below CP, second by second. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- The recovery time constant shortens the further power drops below CP. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- Surges above CP draw on W prime; with short recoveries, it can run low before the decisive moment. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- Recovery is modelled as exponential, fast at first and slower as W prime refills. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- At W'bal zero, power must drop to CP or below; the model predicts exhaustion. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- At long-course intensities W prime is barely used; fuel and durability matter more. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- 60 W x 120 s = 7,200 J, about 7 kJ. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- Later studies found the original recovery constants do not fit all athletes or all interval patterns. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- Large efforts far above CP spend W prime quickly, leaving little for later. (Source: Skiba et al., Med Sci Sports Exerc 2012)
- A larger or faster-recovering W prime lets a rider answer more surges. (Source: Skiba et al., Med Sci Sports Exerc 2012)

## Test 5: The Power-Duration Curve and Durability

- It plots the highest average power achieved over every duration, from seconds to hours. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Maunder described durability as the time and extent of deterioration in physiological profiling characteristics during prolonged exercise. (Source: Maunder et al., Sports Med 2021)
- Thresholds measured fresh can shift after several hours, so fresh values may mislead long-course pacing. (Source: Maunder et al., Sports Med 2021)
- Profiles repeated after, for example, 2,000-3,000 kJ of work show how much each athlete's power declines. (Source: Maunder et al., Sports Med 2021)
- Prolonged exercise can shift thresholds and power outputs downward, with large individual variation. (Source: Maunder et al., Sports Med 2021)
- Comparing 5-second, 1-minute, 5-minute and 60-minute bests reveals sprinter or time-trial tendencies. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Short-duration power reflects VO2max and W prime more than long-duration capacity. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Placing quality efforts after long durations trains the ability to hold power when fatigued. (Source: Maunder et al., Sports Med 2021)
- Simple two-parameter models overpredict power over hours because they omit glycogen depletion and durability. (Source: Jones et al., Med Sci Sports Exerc 2010)
- Same fresh capacity, different fatigue resistance: a durability difference that matters in long races. (Source: Maunder et al., Sports Med 2021)

## Test 6: Pacing Hills and Changing Terrain with Power

- Raising power slightly on climbs and into headwinds and easing where fast gave predicted time savings. (Source: Atkinson et al., J Sports Sci 2007)
- Small variations gave the time savings; larger swings cost more physiologically than they saved. (Source: Atkinson et al., J Sports Sci 2007)
- Time saved per extra watt is greatest where speed is lowest. (Source: Atkinson et al., J Sports Sci 2007)
- At high speed, aero drag dominates so strongly that holding a tuck saves more than pedalling adds. (Source: Atkinson et al., J Sports Sci 2007)
- Big efforts cost disproportionately in glycogen and fatigue compared with the seconds gained. (Source: Abbiss & Laursen, Sports Med 2008)
- Even pacing refers to effort, not constant speed or rigidly fixed watts. (Source: Abbiss & Laursen, Sports Med 2008)
- Accelerating over the crest regains speed when it is lowest, where extra power is worth most. (Source: Atkinson et al., J Sports Sci 2007)
- Extra power helps most on the slow climbing section. (Source: Atkinson et al., J Sports Sci 2007)
- The physiological cost of hard efforts carries into the run, even if bike time barely changes. (Source: Abbiss & Laursen, Sports Med 2008)
- Limiting spikes keeps variability low and saves energy for later, with little time lost. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))

## Test 7: Pacing Strategies and the Evidence

- Reviews conclude even pacing is generally optimal for longer efforts on uniform courses. (Source: Abbiss & Laursen, Sports Med 2008)
- Early excessive effort drains W prime and glycogen and raises fatigue that slows the later stages. (Source: Abbiss & Laursen, Sports Med 2008)
- Athletes' power fell over the bike leg, reflecting fatigue and pacing decisions. (Source: Abbiss et al., Int J Sports Med 2006)
- Knowing the remaining distance or duration helps the brain regulate effort to finish without collapse. (Source: Abbiss & Laursen, Sports Med 2008)
- An end spurt suggests pacing kept a reserve that is released as the finish nears. (Source: Abbiss & Laursen, Sports Med 2008)
- Optimal pacing minimises total time, so the bike effort must leave a strong run. (Source: Abbiss & Laursen, Sports Med 2008)
- Athletes use perceived effort, which grows over the race, to judge whether pace is sustainable. (Source: Abbiss & Laursen, Sports Med 2008)
- Heat raises cardiovascular strain, so the usual power target may be unsustainable. (Source: Abbiss & Laursen, Sports Med 2008)
- Positive pacing means speed decreases over the event; negative pacing means it increases. (Source: Abbiss & Laursen, Sports Med 2008)
- Early overpacing accelerates fatigue, typically costing more time later than it gained. (Source: Abbiss & Laursen, Sports Med 2008)

## Test 8: Power Meter Accuracy and Calibration

- Manufacturers commonly quote accuracies of plus or minus 1-2%. (Source: Maier et al., Int J Sports Physiol Perform 2017)
- Most devices were within a few percent, yet individual units and brands showed meaningful errors. (Source: Maier et al., Int J Sports Physiol Perform 2017)
- Zeroing sets the unloaded baseline so small drifts do not bias all readings. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Strain gauges drift with temperature; many meters compensate, but zeroing after a change helps. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- A static torque check with a known weight at a known crank length verifies the slope. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Chain and sprocket losses of a few percent sit between the two measurement points. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Different measurement points and calibrations mean a few percent difference is common. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- A 3% offset between devices can shift race targets by several watts. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- A meter can be precise (consistent) but inaccurate (offset), which is fine for trends but not for comparisons. (Source: Maier et al., Int J Sports Physiol Perform 2017)
- Zones should match the device being used; retesting avoids training or racing at the wrong intensity. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))

## Test 9: Power Across Conditions and Positions

- VO2max declined about 6-7% per 1,000 m from near sea level, and performance fell with it. (Source: Wehrlin & Hallen, Eur J Appl Physiol 2006)
- Aerobic power drops with altitude, so sea-level targets overestimate what can be held. (Source: Wehrlin & Hallen, Eur J Appl Physiol 2006)
- Lower torso angles close the hip, which can reduce power output and raise metabolic cost. (Source: Fintelman et al., J Biomech 2014)
- Beyond some point, lowering the torso cost more power than it saved in drag, varying with speed. (Source: Fintelman et al., J Biomech 2014)
- Setting race targets from upright testing may overestimate what can be held in the race position. (Source: Fintelman et al., J Biomech 2014)
- Poor airflow raises body temperature and effort at a given power; fans reduce the gap. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- A closed hip angle pushes the abdominal contents up, which can limit ventilation at high efforts. (Source: Fintelman et al., J Biomech 2014)
- Technical sections interrupt steady power and add surges, raising cost at a given average. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- At around 6% per 1,000 m, 1,800 m suggests roughly a 10% drop in aerobic power. (Source: Wehrlin & Hallen, Eur J Appl Physiol 2006)
- Thermal strain lowers sustainable power, so the power-drag trade-off shifts. (Source: Abbiss & Laursen, Sports Med 2008)

## Test 10: Planning the Bike Leg for the Run

- With about 20-25% efficiency, kilojoules of work roughly equal kilocalories of energy expended. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Energy expenditure helps estimate how much carbohydrate is being burned, although intake is limited by absorption. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Software solves the power equation along the course to predict speed and time for a given power plan. (Source: Martin et al., J Appl Biomech 1998)
- Allocating a little more power where speed is low reduces predicted time for the same overall cost. (Source: Atkinson et al., J Sports Sci 2007)
- Decoupling of heart rate from power suggests rising physiological strain that may affect the run. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- A slightly lower bike effort can produce a much better run and a faster total time. (Source: Abbiss & Laursen, Sports Med 2008)
- A controlled run with limited fade suggests the bike effort was sustainable. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Easing slightly and spinning a little faster helps the transition to running without losing much time. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))
- Two rides at the same IF can leave very different fatigue depending on variability, heat and fuel. (Source: Abbiss & Laursen, Sports Med 2008)
- A TSS well above typical guidance points to overcooking the bike relative to their fitness. (Source: Allen, Coggan & McGregor, Training and Racing with a Power Meter (3rd ed., 2019))

Sources: Peer-reviewed sports engineering and physiology literature, with published test data and standards for settled facts

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