Carbohydrate Mouth Rinsing and Softball Batting Performance: a Double-blind Crossover Study
Phase: NA
Conditions: Carbohydrate
Sponsor: National Taiwan Sport University

Carbohydrate mouth rinsing and softball batting performance: a double-blind 
crossover study 
 
Document Date: Oct 21, 2024  
IRB approved date: March 30, 2022 
 
Project summary  
Carbohydrate mouth rinsing (CMR) stimulates the central nervous system and 
improves motor control. However, no studies have examined the effects of CMR on 
softball batting performance. The purpose of this study was to investigate the effect of 
CMR on softball batting performance. Fourteen trained collegiate female softball 
players (age: 20.6±0.9 years; height: 159.5±5.2 cm; body weight: 58.1±6.9 kg) 
completed two trials in a randomization crossover trail, in which they rinsed their 
mouths for 20 seconds with 25 ml of either 6.4% maltodextrin (CMR) or placebo 
(PLA). After rinsing, the grip force, counter-movement jump (CMJ) and batting tests 
were performed in sequence. The tanner tee was utilised to perform five sets of five 
balls at a time, with a minimum of 3 minutes rest between sets. The batting test 
recorded average exit velocity, maximum exit velocity and batting accuracy. The 
standardized standard deviation (SD) for launch angle represents standardized 
variability.  
 
 
 
 
 

Introduction 
 
Many studies have found that pre-exercise carbohydrate supplementation is effective in 
maintaining high levels of glycogen in muscle and improving endurance performance 
in activities exceeding an hour in duration (1, 2). However, since Carter et al. (2004) 
revealed that the use of a carbohydrate mouth rinsing (CMR) still had a significant 
effect on improving athletic performance over a shorter period of time(3), it has been 
shown that CMR not only improves endurance performance over a short period of time, 
but also has a significant effect on high intensity exercise (4), improves resistance 
training quality (5), muscle strength of the lower limbs (6) and decrease fatigue index 
during intermittent exercise(7). The potential mechanism may be due to the delaying of 
fatigue in the central nervous system (8) and may facilitate the activation of the brain 
regions associated with exercise control(9). It has been proposed that the mechanism of 
CMR involves the activation of the dorsolateral prefrontal cortex and the ventral 
striatum (10). The cerebral cortex is integral to cognitive, attentional processing, and 
motivation (11). The aforementioned phenomena suggest that CMR is not only 
beneficial for endurance sports but also enhances performance in explosive sports and 
improves body control during exercise. 
 
In the context of fast pitch softball, enhancing both batting exit velocity and bat control 
represents a crucial strategy for increase the score and win rate of the game(12). In each 
swing, it is necessary to combine speed and explosive power. This can be achieved 
through the use of lower extremity forces, which are employed to transfer weight from 
the lower to the upper body. The rotation of the torso at a rapid pace also serves to 
increase the speed of the swing (13). It has been suggested that increase the muscle 
strength and explosive power of as important factors for improving the exit velocity of 
the ball for female softball players(14). Previous research has demonstrated the efficacy 
of CMR in enhancing lower limb strength, explosive power (6), and potentially 
cognitive function (11). From these perspectives, CMR appears to be a promising 
approach for enhancing both exit velocity and batting control. 
 
CMR has positive effects on athletic performance and activates areas of the brain 
related to motor control (9). For softball batting, an increase in batting speed and stable 
control of the angle of elevation of the bat will improve batting performance and thus 
increase the team's chances of winning. However, there are no studies that have 
examined the effect of CMR on batting performance in softball. Therefore, the purpose 
of this study was to investigate the effect of CMR on the exit velocity and bat control 
of female softball players. 

Methods 
Experimental Design 
This study was conducted using a single-blind randomized cross-over experimental 
design, whereby all participants were required to complete two trials. The carbohydrate 
mouth rinsing trial (CMR) utilised a colourless and odorless water solution, comprising 
6.4% maltodextrin. The mineral water was utilised for the placebo trial (PLA). For each 
rinsing, 25ml of the water solution was used, and the rinsing process was conducted for 
20 seconds before the solution was spat back into the original cup. After completing the 
first experiment, the participant rested for at least 7 days and completed the next 
experiment. 
 
Participants 
A total of 15 female collegiate fast-pitch softball players were recruited for this study. 
Following the withdrawal of one participant due to personal reasons, the final results 
of 14 participants (mean age: 20.6 ± 0.9 years; height: 159.5 ± 5.2 cm; mass: 58.1 ± 5.9 
kg; mean training age: 6.8 ± 0.8 years) were analysed. The inclusion criteria for this 
study were: (a) more than 6 years of professional fast-pitch softball training; (b) more 
than 6 months of continuous training; (c) from at least the top four teams in the country.. 
The exclusion criteria were: (a) non-professionally fast-pitch softball training; (b) lack 
of regular training in the past 6 months; (c) in the event that the applicant has sustained 
a sports injury or is currently experiencing epilepsy, hypertension, hyperlipidemia, heart 
disease, arthritis, osteoporosis, or a brain injury, and has yet to undergo a period of 
recuperation exceeding three months. All participants signed the consent form after 
being informed of the procedure and the associated risks prior to the experiment. All 
tests were completed during non-menstrual periods. The study was approved by the 
institutional review board of China Medical University Hospital, Taiwan (CMUH110-
REC2-253). This study was conducted following the Declaration of Helsinki. 
 
Sample size calculation 
We used G*Power software (version 3.1.9.4, Universität Düsseldorf, Germany) (15) to 
determine the required sample size. The calculation was based on an alpha level of 0.05 
and a correlation coefficient of 0.80, which were deemed to be the appropriate levels 
for the purposes of this study. A previous study demonstrated that CMR enhances lower 
limb muscle strength, with an effect size of 0.56 (6). The analysis revealed that a sample 
size of 14 would be sufficient for the purpose of detecting a difference between trials. 
A sample size of 14 participants should be sufficient to elucidate the statistical 
discrepancies. 
 

Protocol 
 
The formal examination comprises grip strength assessments, CMJ and batting tests. It 
is imperative that all participants undergo familiarisation tests on at least two occasions 
prior to the formal test. Three days prior to the first formal trial, participants were asked 
to photographically record the contents of all meals as well as the time of consumption. 
In the next formal experiment, participants were asked to eat exactly the same food at 
the same consumption time. On the day of the experiment, after a standard lunch at 
12:00, arrive at the laboratory at 15:30 for the experiment.  
 
After a five-minute break, the participants were free to warm up dynamically. All warm-
up movements and times were recorded and the same movements were used for the 
next warm-up. After warming up sufficiently, the participant performs the first rinsing, 
which is followed by a maximum grip strength test with the dominant hand. Perform a 
total of 3 sessions with a 1-minute break between each session. Following the 
completion of the grip strength test, the participant was permitted a three-minute period 
of rest. Subsequently, they rinsed their mouth and proceeded to undertake the CMJ test 
on 3 occasions, with a one-minute interval between each attempt. In previous studies, 
a positive correlation has been identified between grip strength, jump height and the 
exit velocity of a ball in baseball players (16). After completing these tests, participants 
underwent a 5-minute dynamic warm-up of batting. The tanner tee was utilised to 
perform five sets of five balls at a time, with a minimum of 3 minutes rest between sets. 
Participants rinsed their mouths before each batting tests. 
 
Outcome measure 
 
In the grip strength test, the participant assumed a standing position with a standardised 
hand-held grip dynamometer (Smedlay's Hand Grip Dynamometer TTM, Japan) and 
adjusted the grip to the second knuckle, with the arm at an approximately 10° angle to 
the trunk. The participant was instructed to position the grip at an angle of between 0 
and 15 degrees to the trunk and to press the grip continuously for approximately three 
seconds with maximum strength, maintaining stability of the trunk throughout the 
procedure. The procedure was repeated three times, with a one-minute rest interval 
between each repetition, and the resulting data were averaged (17). 
 
A countermovement jump test was conducted utilising a jumping mat (Fusion Sport, 
Coopers Plains, QLD, Australia) to evaluate the participants. The participants were 
instructed to maintain a static standing position on the jumping mat with their arms 

folded at the waist. Subsequently, the subjects were given instructions by the instructor 
and then maintained a position with their arms akimbo, before rapidly squatting to 
approximately 90° of knee flexion before performing a maximal vertical jump. The hip 
and knee joints were maintained in a extended position throughout the jump. Trials in 
which the knee was flexed to an angle of less than 90 degrees or in which the foot made 
contact with the ground were excluded from the analysis. Each participant completed 
three trials, with a one-minute interval between each trial. The mean value was then 
calculated (18).  
 
In the batting test, the tanner tee is used. Place the tanner tee on the front edge of the 
center of the plate and adjust the height of the tanner teet to approximately the navel of 
the test participant. Set the batting target at a 10-degree angle, 10 metres in front of the 
plate, and ask the batter to hit each ball to the target, 5 swings per set, for a total of 5 
sets. Hitting data is collected using Rapsodo Hitting 2.0 (Rapsodo Bassball System, 
Rapsodo Inc, Fishers, IN). This instrument has been employed in previous studies and 
has demonstrated sufficient reliability for the measurement of exit velocity and launch 
angle (19). Batting tests evaluate exit speed of the softball and launch angle, and 
calculated the standard deviation of launch angle, which is used as an indicator of 
batting consistency(19). 
 
Statistical analysis 
The data from this study were presented as mean ± standard deviation and underwent 
analysis using the statistical software package SPSS 23.0. The normality of the data 
was evaluated through the utilisation of the Shapiro–Wilk test. The data are presented 
according to a normal distribution, and a parametric methodology can thus be applied 
to statistical analysis. Paired samples t-tests were employed to ascertain the statistical 
significance of the observed differences in hand grip strength, countermovement jump, 
average batting exit velocity, maximum batting exit velocity and the SD of the launch 
angle. The significance level was set at α<0.05. 
 
 
 
 
 

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