Sports Science

Sports Science for Endurance Athletes

Most endurance sports science reaches runners and other athletes in one of two unsatisfactory forms: academic papers written for researchers, or brand press releases dressed as research. This site has spent fifteen years trying to occupy the ground between them, covering peer-reviewed findings, testing wearable implementations of physiological metrics, and writing up the results for athletes who want to understand what the numbers mean and what to do about them.

The articles collected here span four broad territories.

  • The first is exercise physiology: the underlying science of how endurance performance works. Heart rate variability, VO2max, lactate threshold, ventilatory thresholds, critical power, running economy, fat oxidation, heat adaptation. These are not abstract concepts. Every training decision a serious endurance athlete makes is downstream of how well they understand them. This site has covered each one in depth, from foundational explainers drawing on Jack Daniels, Joe Friel, and Stephen Seiler, through to the most recent wearable implementations of metrics that previously required a laboratory.
  • The second territory is sports science for cyclists and running power science. FTP, critical power, W prime, normalised power, and intensity factor are now standard terms in any serious training platform, yet their physiological basis is rarely explained well outside academic literature. This site has covered cycling power from the Coggan framework through to Garmin’s auto-detection algorithms, aerodynamic drag and its effect on sustainable effort, and the decade-long development of running power as a distinct and contested metric. The question of whether running power is physically meaningful or an instrumented proxy for pace on gradient is still open, and these articles reflect that honestly.
  • The third territory is wearable accuracy science. Consumer devices now claim to measure HRV, ECG, SpO2, VO2max, lactate threshold, skin temperature, and atrial fibrillation. Most of those claims deserve scrutiny. This site has tracked the peer-reviewed validation record since the early days of optical heart rate, covering landmark studies including a 2026 meta-analysis of 39 studies on smartwatch accuracy, independent validation of Garmin HRV against clinical ECG across 62 devices, the AFib EQUAL study comparing Apple Watch to conventional monitoring, and multiple head-to-head comparisons of WHOOP, Oura, and Garmin HRV accuracy during sleep. The cumulative finding is consistent: resting heart rate is generally accurate, HRV is considerably harder to measure reliably, and continuous PPG-based metrics carry systematic error under exercise conditions that most brands do not adequately disclose.
  • The fourth territory is supplementation and nutrition science. Caffeine, dietary nitrates from beetroot and blackcurrant extract, sodium bicarbonate, carbohydrate timing, glucose management, and metabolic flexibility all have genuine peer-reviewed evidence behind them, varying in quality and effect size. This site has covered the primary literature on each, including the European Journal of Applied Physiology research on CurraNZ blackcurrant extract, multiple meta-analyses on beetroot juice and nitric oxide, and race-tested sodium bicarbonate via the Maurten bicarb system. The signal-to-noise ratio in sports nutrition is poor. These articles try to raise it.

A note on what this resource is not. It does not carry the authority of a peer-reviewed journal, and it is not a research database. What it does carry is fifteen years of continuous attention to the intersection of physiology and consumer technology, written by an athlete who has used most of the devices described and who reads the primary literature with the same critical eye applied to a Garmin firmware release. That combination is rarer than it should be.

Key Researchers and Bodies of Work Covered on This Site

Andrew Coggan on functional threshold power, normalised power, intensity factor, and the power training framework that underlies most modern cycling analysis. Stephen Seiler on polarised training intensity distribution and the 80/20 model. Andy Jones and colleagues on dietary nitrates and endurance performance. Jens Bangsbo on lactate dynamics and threshold physiology. Jack Daniels on VDOT and training pace prescription, including the Daniels Tables calculator hosted here. Joe Friel on training zones and the frameworks underlying most modern endurance coaching. Ron George on running power zone methodology, covered in full in the running power zone calculators article. Marco Altini on HRV measurement methodology and the HRV4Training approach. Eric Coyle and the VO2max, lactate threshold, and running economy triad that defines elite endurance capacity. The Firstbeat Analytics team on training load and recovery algorithms embedded across the Garmin device range.

Heart Rate Variability

The deepest cluster on this site. Covers the science, measurement methodology, device accuracy, and practical application of HRV for training and recovery management.

VO2max

Cycling Power: FTP, Critical Power, and the Coggan Framework

FTP was defined by Andrew Coggan as the highest power a rider can sustain in a quasi-steady state without fatiguing. Consumer devices have simplified and in some cases distorted that definition. These articles examine what the metrics actually measure, how Garmin and others calculate them automatically, and where the models break down.

Lactate Threshold, Training Zones, and Load Metrics

This site began publishing training load content in 2011, before most consumer devices tracked anything beyond distance and heart rate. The foundational articles below remain among the most technically detailed on the site.

Running Power

Wearable Accuracy Science

Supplementation and Nutrition Science

Metabolic Science, Glucose, and Fat Oxidation

Sleep Science and Recovery

Recovery Interventions and Treatment Devices

Recovery hardware occupies the least rigorous corner of endurance sports technology. Devices are routinely sold on percentage pain reductions lifted from clinical trials run with different equipment, at doses the manufacturer declines to publish. The articles below treat these products as testable claims rather than wellness purchases, beginning with the dosing science that determines whether any of them can work at all.

Muscle Oxygen and Biomarkers

Training Science and Performance Research

Explore the full resource library

This site covers endurance sport technology across a range of dedicated reference sections. Each one collects the most relevant articles, tests, and analysis on its topic in one place.

Buyer guides

  • Best sports watch — tested recommendations by sport and athlete type: triathlon, running, marathon, cycling, hiking, and women
  • Best Garmin watch — Forerunner versus Fenix by series, sport, and budget
  • Best wearables — recovery trackers, heart rate monitors, running power meters, and female athlete tech
  • Best cycling products — computers, smart trainers, power meters, and cycling heart rate monitors

Brand and product guides

  • Amazfit — the full Amazfit range from Balance to Cheetah to T-Rex, accuracy tests, HYROX partnership, and Zepp Health analysis
  • Apple Watch — athlete-first coverage of Apple Watch across running, cycling, and triathlon
  • COROS — watches, features, and firmware across the full COROS range
  • Garmin — the company, the platform and the full range, and the starting point for choosing across every Garmin product line
  • Garmin Edge — bike computers from entry-level navigation to flagship endurance and mountain biking
  • Garmin Fenix — every model, feature, and firmware development for Garmin's flagship outdoor watch
  • Garmin Fenix 8 Series — which variant to buy, upgrade advice, accuracy data, and the full Fenix 8 review and firmware coverage
  • Garmin Forerunner — the full Forerunner line covered from entry level to triathlon flagship
  • Garmin Instinct — rugged GPS watches for endurance and adventure athletes
  • Garmin Features Explained — how Garmin's metrics work, from Training Load and Body Battery to Race Predictor and HRV Status
  • Google Fitbit — Fitbit Air, Google Health, Pixel Watch and the Wear OS platform
  • Polar — watches, sensors, Polar Flow and training science across the full Polar range
  • Suunto — Race, Vertical, Run and the SuuntoPlus ecosystem
  • Strava — features, privacy, segments, and how Strava fits into a serious training setup
  • Wahoo — KICKR trainers, ELEMNT bike computers, and the Wahoo ecosystem
  • WHOOP — strain, recovery, sleep and the full WHOOP ecosystem

Specifications database

  • Full Specifications Database — detailed spec sheets, battery life, sensor lists and generation-on-generation comparisons for current Garmin, COROS, Amazfit, Samsung, Google Fitbit, Huawei, Polar, Suunto, Wahoo and Apple Watch models

Glossary

  • Sports Technology Glossary — non-branded terminology across running, cycling, swimming, triathlon, hiking, strength training, HYROX, sensors, ecosystems, and brands

Sport and topic guides

  • Running Watches — how to choose by discipline: road racing, trail, track, beginner, and multisport
  • Triathlon and Multisport Technology — watches, sensors, and race-day tools for swimmers, cyclists, and runners
  • HYROX — training science, race analysis, and technology for the functional fitness race format
  • parkrun — technology, training, and performance for the weekly 5K
  • Hiking Technology — navigation, safety, and trail tech for walkers and hikers
  • Heart Rate Monitoring — optical sensors, chest straps, accuracy comparisons, and how to set training zones
  • GPS Accuracy — how satellite systems perform across brands, terrains, and conditions
  • Sports Watch Battery Life — battery claims, real-world tests, and how to manage battery life across Garmin, Apple, Amazfit and Coros
  • Recovery Trackers — WHOOP, Oura, and the science of readiness scoring
  • Female Athlete Tech — wearables, physiology, and performance for female endurance athletes, covering cycle-synced training, RED-S, HR accuracy, and VO2max
  • Sports Science — peer-reviewed research on HRV, VO2max, lactate threshold, running power, wearable accuracy, and supplementation
  • Testing Methodology — how this site tests GPS accuracy, heart rate, battery life, and other performance claims

Content series

  • Release Radar — confirmed launches, leaks, and rumours across Garmin, Apple, COROS, Polar, Suunto, and Wahoo
  • Deep Dive Feature Files — weekly firmware feature updates across all brands (bug fixes excluded)
  • Fix Files — weekly firmware bug fix tracking across all brands