Effect of intensified endurance training on pacing and performance in 4000-m cycling time trials

Studies examining pacing strategies during 4000-m cycling time trials (TTs) typically ensure that participants are not prefatigued; however, competitive cyclists often undertake TTs when already fatigued. This study aimed to determine how TT pacing strategies and sprint characteristics of cyclists change during an intensified training period (mesocycle). Thirteen cyclists regularly competing in A- and B-grade cycling races and consistently training ( > 10 h/wk for 4 [1] y) completed a 6-wk training mesocycle. Participants undertook individually prescribed training, using training stress scores (TrainingPeaks, Boulder, CO), partitioned into a baseline week, a build week, 2 loading weeks (designed to elicit an overreached state), and 2 recovery weeks. Laboratory-based tests (15-s sprint and TT) and Recovery-Stress Questionnaire (RESTQ-52) responses were repeatedly undertaken over the mesocycle. TT power output increased during recovery compared with baseline and loading weeks (P = .001) with > 6-W increases in mean power output (MPO) detected for 400-m sections (10% bins) from 1200 to 4000 m in recovery weeks. Decreases in peak heart rate (P  <  .001) during loading weeks and postexercise blood lactate (P = .005) during loading week 2 and recovery week 1 were detected. Compared with baseline, 15-s sprint MPO declined during loading and recovery weeks (P  <  .001). An interaction was observed between RESTQ-52 total stress score with a 15-s sprint (P = .003) and with a TT MPO (P = .04), indicating that participants who experienced greater stress during loading weeks exhibited reduced performance. To conclude, intensified endurance training diminished sprint performance but improved 4000-m TT performance, with a subtle change in MPO evident over the last 70% of TTs

Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability

We investigated substrate utilisation during exercise after brief (5–6 days) adaptation to a ketogenic low-carbohydrate (CHO), high-fat (LCHF) diet and similar washout period. Thirteen world-class male race walkers completed economy testing, 25 km training and a 10,000 m race (Baseline), with high CHO availability (HCHO), repeating this (Adaptation) after 5–6 days’ LCHF (n = 7; CHO: 200%) increases in exercise fat oxidation occurred in the LCHF Adaptation economy and 25 km tests, reaching mean rates of ∼1.43 g min−1. However, relative urn:x-wiley:00223751:media:tjp14268:tjp14268-math-0001 (ml min−1 kg−1) was higher (P < 0.0001), by ∼8% and 5% at speeds related to 50 km and 20 km events. During Adaptation race warm-up in the LCHF group, rates of fat and CHO oxidation at these speeds were decreased and increased, respectively (P < 0.001), compared with the previous day, but were not restored to Baseline values. Performance changes differed between groups (P = 0.009), with all HCHO athletes improving in the Adaptation race (5.7 (5.6)%), while 6/7 LCHF athletes were slower (2.2 (3.4)%). Substrate utilisation returned to Baseline values after 5–6 days of HCHO diet. In summary, robust changes in exercise substrate use occurred in 5–6 days of extreme changes in CHO intake. However, adaptation to a LCHF diet plus acute restoration of endogenous CHO availability failed to restore high-intensity endurance performance, with CHO oxidation rates remaining blunted

Linear mixed model data for the resting metabolic rate (RMR) model.

<p>Linear mixed model data for the resting metabolic rate (RMR) model.</p

Percentage change in measured variables from baseline in relation to training load across the study duration for A) RMR, B) Body mass, C) Total energy intake, D) Appetite, E) Mood disturbance, F) Biochemical markers leptin and fT3, G) Heart rate variability (LnRMSSD), and H) Cycling performance.

<p>The left y-axis depicts Δ% in each of the measured variables, with Δ% in training load on the right y-axis, shaded beneath the curve.</p

Study design showing the training load undertaken in TSS points per week, the training sessions prescribed, and the corresponding physiological and perceptual measures taken.

<p>Key: Monitored Laboratory Session—consisting of the standardised warm up, assessment of cycling performance, and HIIT training session; Biochemical Markers—PRE and POST warm up blood samples for leptin and fT3; On-road Cycling Session– 1) long duration, aerobic-based session and 2) hill repeats; Power Meter Calibration—timed repetition of a known distance and elevation; RMR—Resting Metabolic Rate; Body Composition—from Dual-Energy X-Ray Densitometry (DXA); Energy Intake—from 3-day food diaries; Appetite—visual analogue scales to determine appetite; Mood Questionnaire—consisting of the Multicomponent Training Distress Scale, Recovery Stress Questionnaire for Athletes (RESTQ-52 Sport); HRV—Heart Rate Variability. The spotted bars indicate a laboratory-training day; the striped bars indicate an on-road cycling training day; the white bars indicate a rest day.</p

Training load.

<p>Data are presented as (mean ± SD) for the actual TSS achieved by the participants on the left y-axis, and the corresponding Δ% in TSS from Baseline on the right y-axis.</p

Outline of the monitored laboratory sessions and assessment of cycling performance.

<p>Outline of the monitored laboratory sessions and assessment of cycling performance.</p

The effects of intensified training on resting metabolic rate (RMR), body composition and performance in trained cyclists

<div><p>Background</p><p>Recent research has demonstrated decreases in resting metabolic rate (RMR), body composition and performance following a period of intensified training in elite athletes, however the underlying mechanisms of change remain unclear. Therefore, the aim of the present study was to investigate how an intensified training period, designed to elicit overreaching, affects RMR, body composition, and performance in trained endurance athletes, and to elucidate underlying mechanisms.</p><p>Method</p><p>Thirteen (n = 13) trained male cyclists completed a six-week training program consisting of a “Baseline” week (100% of regular training load), a “Build” week (~120% of Baseline load), two “Loading” weeks (~140, 150% of Baseline load, respectively) and two “Recovery” weeks (~80% of Baseline load). Training comprised of a combination of laboratory based interval sessions and on-road cycling. RMR, body composition, energy intake, appetite, heart rate variability (HRV), cycling performance, biochemical markers and mood responses were assessed at multiple time points throughout the six-week period. Data were analysed using a linear mixed modeling approach.</p><p>Results</p><p>The intensified training period elicited significant decreases in RMR (F_(5,123.36) = 12.0947, p = <0.001), body mass (F_(2,19.242) = 4.3362, p = 0.03), fat mass (F_(2,20.35) = 56.2494, p = <0.001) and HRV (F_(2,22.608) = 6.5212, p = 0.005); all of which improved following a period of recovery. A state of overreaching was induced, as identified by a reduction in anaerobic performance (F_(5,121.87) = 8.2622, p = <0.001), aerobic performance (F_(5,118.26) = 2.766, p = 0.02) and increase in total mood disturbance (F_{(5, 110.61)} = 8.1159, p = <0.001).</p><p>Conclusion</p><p>Intensified training periods elicit greater energy demands in trained cyclists, which, if not sufficiently compensated with increased dietary intake, appears to provoke a cascade of metabolic, hormonal and neural responses in an attempt to restore homeostasis and conserve energy. The proactive monitoring of energy intake, power output, mood state, body mass and HRV during intensified training periods may alleviate fatigue and attenuate the observed decrease in RMR, providing more optimal conditions for a positive training adaptation.</p></div