Table 1 Overview of the subjects, strategies, performance changes and PEDro scores of the included studies
Study | Subjects | VO2max (ml·kg− 1·min− 1) | ”Train-low” strategy | Changes in endurance performance | PEDro score |
|---|---|---|---|---|---|
Yeo et al. 2008 [40] | 14 male cyclists Low: n = 7 High: n = 7 | Low: 60 High: 61 | ”Twice-a-day” every second day vs. “Once-a-day” every day 6 sessions (3 AT and 3 HIIT) per week for 3 weeks HIIT commenced with low vs. high muscle glycogen Athletes instructed to consume of 8-9 g CHO ·kg− 1·day− 1 throughout the period Total training volume: 7 h·week− 1 | Low = High 60 min preload + 60 min TT 10–12% increase in PO during TT in both groups (P < 0.01) | 5 |
Hulston et al. 2010 [41] | 14 male cyclists Low: n = 7 High: n = 7 | Low: 65 High: 66 | ”Twice-a-day” every second day vs. “Once-a-day” every day 6 sessions (3 AT and 3 HIIT) per week for 3 weeks HIIT commenced with low vs. high CHO availability Athletes instructed to consume high CHO diet throughout the period Total training volume: 7.5 h·week− 1 | Low = High 60 min preload + 1017 ± 73 kJ TT 10–11% increase in PO during TT in both groups (P < 0.001) | 6 |
Cox et al. 2010 [42] | 16 male triathletes Low: n = 8 High: n = 8 | Groups combined: 65 | “Fasted training” vs. training with high CHO availability 6 sessions per week for 23 days 5 g CHO·kg− 1·day− 1 in both groups High: + 1.5 g CHO·kg− 1·day− 1 for every hour of exercise Low: + 25 kJ·kg− 1·day− 1 for every hour of exercise from fat and protein Low: fasting for 2 h prior to and during all sessions High: ingestion of CHO before or during all sessions | Low = High 100 min preload + 7 kJ/kg TT 4–6% reduced time in TT in both groups (P < 0.01) | 6 |
Marquet et al. 2016 [43] | 21 male triathletes Low: n = 11 High: n = 10 | Low: 60 High: 60 | ”Sleep-low” 3x CHO periodization per week for 3 weeks Identical diets in both groups but different timing 0 g vs. 5 g CHO·kg− 1 during and between afternoon and morning sessions Additional AT sessions in both groups Total training volume: 10-15 h·week− 1 | Low > High 40 km bike preload + 10 km run − 2.9% run time in Low (P < 0.01) − 0.1% run time in High (ns) | 6 |
Marquet et al. 2016 [44] | 21 male cyclists Low: n = 12 High: n = 9 | Groups combined: 64 | ”Sleep-low” 3x per week for 1 week Identical diets in Low and High around “train-low” sessions but different timing 0 vs. 5 g CHO·kg− 1 between afternoon HIIT and morning AT. Total training volume: 5 h during the 6-day training period. | Low > High 120 min preload + 20 km TT − 3% TT time in Low (P < 0.05) − 1% TT time in High (ns) | 6 |
Burke et al. 2017 [6] | 19 male elite race walkers Low: n = 10 High: n = 9 | Low: 65 High: 62 | “Fasted training”, “Sleep-low” and “Twice-a-day” Alternating strategies 6 days per week for 3 weeks Identical energy and CHO intake low and high but different timing. Average total training volume: Low: 125 km·week− 1; High: 117 km·week− 1 | Low = High 10 km race walking 5–7% reduced walking time in both groups (P < 0.01) | 5 |
Gejl et al. 2017 [45] | 26 male triathletes and cyclists Low: n = 13 High: n = 13 | Low: 65 High: 65 | ”Twice-a-day” 6 sessions (3 HIT and 3 AT) per week for 4 weeks 1 g vs. 6 g CHO · kg− 1 between HIT and LIT sessions (isocaloric diets) Additional AT sessions to attain habitual training volume Average total training volume in matched pairs of athletes: 16 h·week− 1 | Low = High 90 min preload + 30 min TT 5–6% increase in PO during TT in both groups (P = 0.0003) | 6 |
Riis et al. 2019 [46] | 13 male endurance athletes Low: n = 6 High: n = 7 | Low: 63 High: 65 | ”Sleep-low” 6 sessions (3 HIT and 3 AT) per week for 4 weeks Identical diets but different timing. 0 vs. 3.6 g CHO·kg− 1 between afternoon HIIT and morning AT Total training volume: 6hrs45min·week− 1 | Low = High 90 min preload + 30 min TT 14–19% increase in PO during TT in both groups (P = 0.005) | 7 |
Burke et al. 2020 [8] | 16 elite race walkers Low: n = 5 males n = 3 females High: n = 5 males n = 3 females | Low: 59 High: 58 | “Fasted training”, “Sleep-low” and “Twice-a-day” Alternating strategies 6 days per week for 25 days Identical energy intake in Low and High but different timing Average total training volume: 113 and 106 km·week− 1 in Low and High. | Low = High 10 km race walk − 2.2% walk time in Low (P = 0.09) − 4.8% walk time in High (P < 0.001) | 5 |