Six weeks of a polarized training-intensity distribution leads to greater physiological and performance adaptations than a threshold model in trained cyclists

Abstract

This study was undertaken to investigate physiological adaptation with two endurance-training periods differing in intensity distribution. In a randomized crossover fashion, separated by 4 wk of detraining, 12 male cyclists completed two 6-wk training periods: 1) a polarized model [6.4 (±1.4 SD) h/wk; 80%, 0%, and 20% of training time in low-, moderate-, and high-intensity zones, respectively]; and 2) a threshold model [7.5 (±2.0 SD) h/wk; 57%, 43%, and 0% training-intensity distribution]. Before and after each training period, following 2 days of diet and exercise control, fasted skeletal muscle biopsies were obtained for mitochondrial enzyme activity and monocarboxylate transporter (MCT) 1 and 4 expression, and morning first-void urine samples were collected for NMR spectroscopy-based metabolomics analysis. Endurance performance (40-km time trial), incremental exercise, peak power output (PPO), and high-intensity exercise capacity (95% maximal work rate to exhaustion) were also assessed. Endurance performance, PPOs, lactate threshold (LT), MCT4, and high-intensity exercise capacity all increased over both training periods. Improvements were greater following polarized rather than threshold for PPO [mean (±SE) change of 8 (±2)% vs. 3 (±1)%, P < 0.05], LT [9 (±3)% vs. 2 (±4)%, P < 0.05], and high-intensity exercise capacity [85 (±14)% vs. 37 (±14)%, P < 0.05]. No changes in mitochondrial enzyme activities or MCT1 were observed following training. A significant multilevel, partial least squares-discriminant analysis model was obtained for the threshold model but not the polarized model in the metabolomics analysis. A polarized training distribution results in greater systemic adaptation over 6 wk in already well-trained cyclists. Markers of muscle metabolic adaptation are largely unchanged, but metabolomics markers suggest different cellular metabolic stress that requires further investigation.

The Ingestion of 39 or 64 g·hr−1 of Carbohydrate is Equally Effective at Improving Endurance Exercise Performance in Cyclists

“…Individual lactate responses were examined independently by two researchers to ensure validity and consistency of the analysis. The mean ± SD lactate concentration at LT was 2.1 ± 0.4 mmol·L corresponding to an intensity of 52 ± 6% of PPO for LT which is typical of other studies utilising a similar protocol (Neal et al, 2013).…”

From Heart-Rate Data to Training Quantification: A Comparison of 3 Methods of Training-Intensity Analysis

“…Critically, the distribution ratio is often based on different methods (time-based allocation vs. categorical allocation) and athletes at different levels, making comparisons across studies difficult. While our sample athletes employed a nationally standardized 5-zone aerobic intensity scale, we chose to convert their training data to the same 3-zone intensity scale, anchored around VT 1 /LT 1 and VT 2 /LT 2 , that has been most frequently used in research on training intensity distribution [10][11][12][21][22][23][24] , as well as intensity distribution during long single-day 13 and multi-day events [4][5] .…”

“…No study since has systematically quantified TID derived from three different methods in highly trained athletes. The TID of endurance athletes has received increased attention in both descriptive [1][2][3][6][7][8][9][10][11][12][13]18,20 and experimental studies [21][22][23] as well as recent reviews 24,25 . Because these three methods are used interchangeably there can be confusion regarding interpretation of training data, although the problem has been discussed 12 .…”

“Functional” Respiratory Muscle Training During Endurance Exercise Causes Modest Hypoxemia but Overall is Well Tolerated

“…Such training is already known to elicit superior adaptations in maximal oxygen consumption, running economy, and run performance (8,18,28). Perhaps incorporating the training mask into some of this low-intensity conditioning may further these benefits.…”