Table 1 Studies included in the systematic review and meta-analysis
Study | # Of participants | # Of training hours per week | V̇O2peak (mL·kg·−1 min−1) | Modality | Exercise and outcome description | Environmental conditions | MR concentration | MR frequency | Total # of MR | Swilling duration | MR comparison | Difference | Significant performance or capacity effect |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mundel and Jones [12] | 9 M | NR | 54 (5) | Cycle | 65% of Wmax to exhaustion | 34 (1) °C, 27 (4) % RH | 0.01% | Every 10 min | Variable | 10 s | Orange-flavoured placebo | 7.9% | p = 0.043 |
Stevens et al. [13] | 11 M |  > 4 h | NR | Run | 5-km time trial | 32.6 (0.2) °C, 45.8 (5.7) %RH | 0.01% | At the 0.2 km mark of every 1 km | 5 | 5 s | Control—no mouth rinse | 2.7% | p < 0.01 |
Flood et al. [10] | 8 M |  > 5 h | 55.4 (6) | Cycle | RPE 16/20 to exhaustion | 35.0 (0.8) °C, 47.8 (2.3) %RH | 0.01% | 1.5 min prior and every 10 min during (− 1:30, 8:30, 18:30 min) | 3 | 5 s | Apple favoured non-calorific artificial sweetener (sucralose) | 7.1% | p = 0.049 |
Gibson et al. [11] | 11 M, 3 F | NR | 46.2 (12.9) | Cycle | 40-min intermittent sprint protocol: Wpeak and work done | 40.2 (0.6) °C, 42 (2) %RH | 0.01% | Before and every 10 min throughout | 4 | 5 s | Water | 0% | p = 0.981 |
Gibson et al. [11] | 11 M, 3 F | NR | 46.2 (12.9) | Cycle | 40-min intermittent sprint protocol: Wpeak and work done | 40.2 (0.6) °C, 42 (2) %RH | 0.01% | Before and every 10 min throughout | 4 | 5 s | 0.3 sham-carbohydrate orange flavoured | 1.4% | p = 0.981 |
Jeffries et al. [3] | 11 M | NR | 52.4 (5.3) | Cycle | 70% Wmax with self-selected cadence to exhaustion | 35 (0.2) °C, 40 (0.5) %RH | 0.01% | MR at 85% of time to exhaustion baseline | 1 | 5 s | Raspberry-flavoured non-calorific | 4.4% | p = 0.036 |
Jeffries et al. [3] | 11 M | NR | 52.4 (5.3) | Cycle | 70% Wmax with self-selected cadence to exhaustion | 35 (0.2) °C, 40 (0.5) %RH | 1.25 g/kg | 85% of time to exhaustion baseline | 1 | 5 s | Cold water with ice | − 1.6% | p > 0.05 |
Saldaris et al. [14] | 12 M | NR | 61.3 (2.6) | Run | 3 × 30 min at 65% VO2peak and TTE run at 100% VO2 pea | 35.3 (0.3) °C, 59.2 (2.5) %RH | 0.1% | Prior to trial, 15 and 30 min point of each run block, and prior to the TTE run | 10 | 5 s | Control—no mouth rinse | 34.4% | p = 0.020 |
Best et al. [15] | 10 M, 9 F |  > 2 h for + 3 months prior | NR | Dynamometer | Isometric mid-thigh pulls mean force (max strength/power) 3 × 3-s max effort separated by 3-min rest | 22 (1) °C, NR | 0.1% | 60 s prior to each exercise | 9 | 10 s | Control—no mouth rinse | 0.5% | p = 0.002 |
Best et al. [15] | 10 M, 9 F |  > 2 h for + 3 months prior | NR | Legs | Vertical jump height 3 × 3-s max effort separated by 3-min rest | 22 (1) °C, NR | 0.1% | 60 s prior to each exercise | 9 | 10 s | Control—no mouth rinse | 0.5% | p = 0.013 |
Best et al. [15] | 10 M, 9 F |  > 2 h for + 3 months prior | NR | Cycle | 6-s sprint average power 3 × 3-s max effort separated by 3-min rest | 22 (1) °C, NR | 0.1% | 60 s prior to each exercise | 9 | 10 s | Control—no mouth rinse | 0.5% | p = 0.120 |
Gavel et al. [7] | 9 F | 14.3 (2.9) | 50.8 (6) | Cycle | 30-km time trial | 30 (0.6) °C, 70 (1) %RH | 0.01% | Every 5 km | 5 | 5 s | Non-caloric berry-flavoured sweetener (sucralose) | 2.2% | p = 0.034 |
Parton et al. [4] | 11 M |  < 5 | 53.9 (6.9) | Cycle | RPE 16/20 to exhaustion | 34.9 (0.5) °C, 40.6 (2.2) %RH | 0.01% | 30 s prior to and at 10-min intervals (− 0:30, 9:30, 19:30 min) | Variable | 10 s | Apple flavoured non-calorific artificial sweetener (sucralose) | 6.5% | p = 0.039 |
Parton et al. [4] | 11 F |  < 5 | 43.5 (2.9) | Cycle | RPE 16/20 to exhaustion | 34.9 (0.5) °C, 40.6 (2.2) %RH | 0.01% | 30 s prior to and at 10-min intervals (− 0:30, 9:30, 19:30 min) | Variable | 10 s | Apple flavoured non-calorific artificial sweetener (sucralose) | 2.2% | p = 0.475 |
Crosby et al. [16] | 6 M, 6 M | 3–7 | NR | Cycle | 3-min all out | 33 (3) °C, 46 (5) %RH | 0.1% | 66% (2 min) of time trial | 1 | 5 s | Cold water (< 4 °C) | NR | p = 0.540 |
Crosby et al. [16] | 6 M, 6 M | 3–7 | NR | Cycle | 3-min all out | 33 (3) °C, 46 (5) %RH | 0.1% | 66% (2 min) of time trial | 1 | 5 s | Peppermint | NR | p = 0.540 |
Jerram et al. [24] | 27 M |  > 10 training sessions per week | NR | 15-a-side rugby-specific conditioning blocks | Distance per minute | 26.8 (1.6)°C, 58.2 (3.4) %RH | 0.1% | Warm-up (55 min), 3-min rugby-specific conditioning block, 1-min rest, 3-min rugby-specific conditioning block, 1-min rest, 30 min of further training | 3 | 5 s | Water | 0.5% | p = 0.257 |