Skip to main content

Table 1 Overview of the subjects, strategies, performance changes and PEDro scores of the included studies

From: Performance effects of periodized carbohydrate restriction in endurance trained athletes – a systematic review and meta-analysis

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
  1. AT moderate-to-high intensity aerobic training, CHO carbohydrate, High control group receiving CHO, HIIT high intensity interval training, LIT low intensity training session, Low “train-low” group exposed to periodized fasting or CHO restriction, MAP maximal aerobic power, PO power output, TT cycling time trial, VO2max maximal oxygen consumption