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Jem Arnold

Author: Jem Arnold

Why Perform Hard-Start VO2max Intervals?

Hard-start intervals use an initial hard effort at a power output above what would be sustainable for the intended interval duration, to enhance oxygen uptake and cardiac output. Let's talk about some of the reasons for why we might want to perform hard-start intervals, when they might be appropriate for our training, and when they might not be.

Jem Arnold Science Review, Training Optimization 8 Comments December 9, 2020January 8, 2021 13 Minutes

Call For Participants (closed)

We are looking for subjects to participate in a remote cycling training study we are conducting through the University of Toronto, in partnership with TrainerRoad. This study will investigate the effects of high intensity interval training (HIIT) on cycling performance. If you are interested in participating and want more information, please go to

Jem Arnold Science Review 1 Comment November 19, 2020September 29, 2021 2 Minutes

Workload, Intensity, and VO2max Trainability

Here are some of my current thoughts and questions on the topic of VO2max trainability, time near VO2max, hard-start and intermittent intervals, and adaptations toward capacity and efficiency.

Jem Arnold Science Review, Training Optimization 22 Comments June 30, 2020January 7, 2021 12 Minutes

Muscle Oxygenation Overview

Muscle Oxygenation refers to the flux of oxygen within a target tissue as the result of oxidative respiration. Delivery of oxygenated blood from the heart & lungs and uptake or extraction of oxygen by the mitochondria within the local muscle. This is measured with a technology called near-infrared spectroscopy (NIRS)

Jem Arnold Science Review 7 Comments June 17, 2020January 7, 2021 10 Minutes

Internal Training Load Measurement with Muscle Oxygenation

A recent finding in our research with Moxy muscle oxygenation was looking at the reliability & repeatability of muscle oxygen saturation (SmO2) compared to heart rate for a typical high intensity interval workout. We had a group of well-trained male subjects (VO2max > 60 ml/kg/min) perform a series of 4x4min high intensity

Jem Arnold Performance Assessment 8 Comments June 11, 2020January 7, 2021 6 Minutes

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Recent Popular Posts

  • 2017 Training Part 3 - VO2max
  • Comparing Metabolic Response to Hard-Start VO2max Intervals
  • Sustainable Training
  • The Problem with VO2max
  • Why Perform Hard-Start VO2max Intervals?

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My name is Jem Arnold

I write about physiology and endurance training optimization.

I’m an Exercise Physiology PhD student, Physiotherapist, and endurance coach/consultant.

I try to integrate ideas from the perspectives of an athlete, health professional, coach, researcher, and especially as a curious enthusiast who just wants to learn from the smartest people in whatever virtual room I find myself in.

Everything written is my own inexpert opinion. Any good ideas should be attributed to all of the smart people I have learned from. Any bad ideas are due to my own temporary misunderstanding. My current opinions will most certainly change as I continue to learn. Nothing written constitutes professional advice.

Recent Posts

  • Thresholds, Constructs, and Confidence Intervals
  • Sustainable Training
  • Predicting Cycling Time To Exhaustion from Paraspinals Muscle Oxygenation
  • Evaluating the Relationships between Muscle Oxygenation, Ventilation, and Lactate Thresholds
  • CoreTemp Heat Accumulation Test
  • Why Perform Hard-Start VO2max Intervals?
  • Call For Participants (closed)
  • Workload, Intensity, and VO2max Trainability
  • Muscle Oxygenation Overview
  • Internal Training Load Measurement with Muscle Oxygenation
  • Speculating on Physiology in the Lab vs on the Road
  • Comparing VO2 Master Pro to TrueOne 2400 – Part 2
  • Comparing VO2 Master Pro to TrueOne 2400 – Part 1
  • Surgery Race Report
  • Modeled VO2 During Ramp Tests and Intervals
  • Metabolic Steady State – Inside vs Outside
  • Deriving Power from VO2 and VO2 from Power
  • VO2 Measured to Modeled
  • Comparing 30/15 VO2max Intervals
  • More Comparisons for Hard-Start VO2max
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