Heavy-, Severe-, and Extreme-, but Not Moderate-Intensity Exercise Increase V̇o 2max and Thresholds after 6 wk of Training

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Title: Heavy-, Severe-, and Extreme-, but Not Moderate-Intensity Exercise Increase Vo˙ 2max and Thresholds After 6 Weeks of Training.
Authors: Erin Calaine Inglis, Danilo Iannetta, Letizia Rasica, Mary Z. Mackie, Daniel A. Keir, Martin J. MacInnis, Juan M. Murias.
Affiliations: University of Calgary, Western University, Hamad Bin Khalifa University.
Published in: Medicine and Science in Sports and Exercise, Vol. 56, No. 7, 2024.

Purpose: To assess the impact of individualized, domain-based exercise intensity prescription on maximal oxygen uptake (VO˙ 2max) and submaximal thresholds.
Participants: 84 young healthy individuals (42 females, 42 males).
- Groups: Moderate (MOD), Lower heavy (HVY1), Upper heavy (HVY2), High-Intensity Interval Training (HIIT), Sprint-Interval Training (SIT), and Control (CON).
Findings: All training groups except MOD showed significant increase in VO˙ 2max.

VO˙ 2max: Maximum rate of oxygen consumption.
Thresholds: Specific points at which there is a notable change in exercise intensity response, e.g., lactate threshold (LT).
Intensity Domains:
- Moderate: Below LT
- Heavy: Between LT and Maximal Metabolic Steady State (MMSS)
- Severe: Above MMSS
- Extreme: Above MMSS, involving maximal efforts.

VO˙ 2max Change:
- HIIT: +6.2 ± 2.8 mL·kg−1·min−1
- HVY2: +5.4 ± 2.3
- SIT: +4.7 ± 2.3
- HVY1: +3.3 ± 2.4
- MOD: +1.8 ± 2.7
- CON: +0.1 ± 1.2
Significance: Changes were significant for HIIT, HVY2, SIT, HVY1 compared to control.

Intensity as a Variable: Critique of current exercise intensity prescriptions which often rely on percentage of VO˙ 2max or HRmax, which can vary greatly between individuals.
Metabolic Disturbance: The metabolic response and necessary adjustments in training intensities to achieve specific adaptations.
Reevaluation of Guidelines: Current guidelines based on percentages may not effectively lead to consistent fitness improvements.

Using ventilatory/lactate thresholds may enhance precision in exercise intensity classification.
Misclassification can lead to varied responses to training across individuals, complicating the synthesis of training results in literature.

Demographic: Healthy young adults, randomized into groups ensuring matched characteristics.
Testing: Measured VO˙ 2, heart rates, and physiological responses through metabolic carts and blood lactate samples.
Training: 6-week program for each group, with physiological evaluations before, mid-way, and after the intervention.

Equipment: Metabolic cart for gas exchange measurement, heart rate monitoring systems, lactate analyzers.
Maximal Sessions: Included ramp incremental tests to task failure, determining VO˙ 2max, maximal power output, and lactate thresholds.
Constant workload trials: Used to establish metabolic steady state (
MMSS).

Approach: Utilized two-way mixed ANOVA to evaluate potential changes over time and between groups.
Effect Size: Indicators used to represent the magnitude of differences among groups.

Analysis revealed significant improvements across HIIT, HVY2, and HVY1 in both VO˙ 2max and maximal lactate thresholds (θLT) post-intervention, contrasting with MOD group’s lack of improvement.
Minimum Intensity Stimulus: Highlights a necessary intensity threshold for improvements in physiological variables.

Training Adaptation: Individuals may require more intense training than what current moderate-intensity guidelines suggest to achieve significant fitness enhancements.
Framework Development: Calls for a structured and scientifically-informed method of prescribing exercise intensities tailored to individual thresholds for maximal effectiveness.

Future guidelines should account for interindividual variability in exercise responses and recommend threshold-based training for different populations, including clinical and elderly groups.
Holistic Approach: Incorporate exercise prescription that fully considers the roles of both intensity and duration in training effectiveness.

Key Findings: Importance of exercise intensity domain-based prescription in maximizing VO˙ 2max improvements and optimizing training adaptations.
Recommendation: A paradigm shift towards a domain-specific approach in developing exercise guidelines to enhance training outcomes across diverse populations.