Carbohydrate Mouth Rinses and Caffeine Gum Increase the Romanian Deadlift Performance on the Flywheel Training Device: A Randomised, Cross-Over Study
Phase: NA
Conditions: Carbohydrate, Caffeine
Sponsor: National Taiwan Sport University

Effect of Carbohydrate Rinsing and Caffeine Gum Intervention on 
Performance of Romanian Deadlifts on Flywheel Training Device 
 
Project summary 
We explored the effect of Carbohydrate Rinsing and 200mg of caffeine caffeine gum 
chewing on the performance of romanian deadlifts on flywheel training device. We 
recruited 20 healthy adult men who in this study. In study 1, participants were randomly 
allocated to the Carbohydrate Mouth Rinsing (CMR) and placebo (PL) groups. In study 
2, participants were randomly allocated to the caffeine gum chewing (CG) and placebo 
(PL) groups and subjected to a crossover experiment in which they performed 
maximum inertial resistance training comprising five sets of six reps, with 3-min rests 
between sets. After deducting the first repetition of each sets, the mean values from the 
five sets were analyzed. 
 
General information 
 
Protocol title: Effect of Carbohydrate Rinsing and Caffeine Gum Intervention on 
Performance of Romanian Deadlifts on Flywheel Training Device (Date: 18/03/2022; 
ID: NA) 
Funder: This study was funded by Ministry of Science and Technology in Taiwan 
(106, Sec. 2, Heping E. Rd., Taipei 10622, Taiwan). 
Authors: Chih-Hui Chiu1, Che-Hsiu, Chen2, Min-Huan Wu3, Yu-Chen Hsieh4, Zong-
Yan, Lin5, Bo-Wei Chen6  
 
1Graduate Program in Department of Exercise Health Science, National Taiwan 
University of Sport, Taichung 404, Taiwan; chiuch@ntus.edu.tw. 
2Department of Sport Performance, National Taiwan University of Sport, Taichung 
404, Taiwan; jakic1114@ntus.edu.tw 
3Sport Recreation and Health Management Degree Program, Tunghai University, 
Taichung 404, Taiwan; mhwu@thu.edu.tw 
4Graduate Program in Department of Exercise Health Science, National Taiwan 
University of Sport, Taichung 404, Taiwan; 10806008@gm.ntus.edu.tw 
5Graduate Program in Department of Exercise Health Science, National Taiwan 
University of Sport, Taichung 404, Taiwan; 10806005@gm.ntus.edu.tw 
6Graduate Program in Department of Exercise Health Science, National Taiwan 
University of Sport, Taichung 404, Taiwan; 10906007@gm.ntus.edu.tw 
Clinical laboratory: National Taiwan University of Sport (No. 16, Sec. 1, Shuangshi 
Rd., North Dist., Taichung City 404401 , Taiwan) 

 
 
  
Introduction 
In the early 20th century, carbohydrates were discovered to be a crucial source of 
energy for exercise(1). During prolonged endurance exercise, carbohydrate intake helps 
maintain blood glucose concentrations, exercise reaction times, and technical 
performance(2, 3). However, even during shorter, higher-intensity exercise (e.g., < 1 
hour, 75% V
‧O2max), carbohydrate intake can improve exercise performance(1). For 
this reason, muscle glycogen depletion is not considered a performance-limiting factor, 
and other factors may enhance performance during high-intensity exercise(4). 
Studies have had participants gargle an aqueous solution of CHO in the oral cavity 
for several seconds and spit it out. This method was associated with improved 
performance during endurance activities(5). During mouth rinsing, the CHO in the 
aqueous solution travels to the neural sensors in the oral cavity, which improves the 
performance of the nerve signals transmitted to the brain; this provides indirect 
evidence of the strengthening of the central nervous system effect(4). Rinsing the mouth 
with CHO solution and then spitting it out can also prevent gastrointestinal discomfort 
caused by the ingestion of CHO and the conflict between improving sports performance 
and the ingestion of CHO for those with weight control needs; this method also provides 
new reference for the supplementation of CHO in sports performance. 
A study on aerobic exercise conducted a long-distance cycling test after 
participants gargled a 6.4% CHO solution. During exercise, the average power, overall 
power, and climbing power increased, and perceived levels of fatigue decreased(6). 
However, studies on the effects of CHO-solution mouthwashes on short-term, high-
intensity exercise and resistance training have yielded inconsistent results. Decimoni et 
al. (2018) discovered that rinsing the mouth with a CHO solution before resistance 
exercise can reduce fatigue and enable weightlifters to lift heavier loads during 
resistance exercise(7). However, another study observed that gargling different doses 
of CHO solution (6%, 12%, and 18%) before resistance exercise did not improve 
maximal muscle strength or muscle endurance(8). Whether rinsing the mouth with 
CHO solution before resistance exercise improves performance remains to be further 
explored. On the other hand, it remains to be studied whether chewing caffeinated gum 
can also enhance inertial resistance exercise performance. 
Flywheel resistance training, a type of eccentric load training, has been widely 
discussed and used for various sports. In flywheel resistance training, inertial power 
generated by the flywheel during muscle acceleration and deceleration provides 
resistance in the eccentric and concentric phases, respectively(9). The flywheel has 
been demonstrated to improve health and athletic performance and prevent sports 
injury(10). No studies have examined the effect of rinsing the mouth CHO solution on 
the performance of inertial resistance exercise. For this reason, this study investigated 
the effect of carbohydrate mouth rinsing (CMR) on inertial resistance exercise 
performance. 
 
Methods 
Participants 
    This study recruited 20 healthy adult men (age: 22.4±3.7yr, height: 171.3±5.9cm, 
weight: 76.4±11±kge). The inclusion criteria were (1) regular weight training habits, (2) 

familiarity with Romanian deadlift movements, and (3) no chronic diseases such as 
hypertension, diabetes, and kidney disease or sports injuries such as lacerated knee 
ligaments, inflammation and rupture of tendons, strained biceps femoris or quadriceps, 
and strained biceps within the 6 months prior. Those who (1) did not have regular 
exercise habits, (2) were unfamiliar with Romanian deadlift movements, and (3) had 
certain health problems that prevented them from performing exercise or injury from 
which they had not recovered for more than 6 months were excluded. Before the 
experiment, the researchers explained the experimental procedure to the participants 
and obtained their informed consent. This study was approved by the Human Subject 
Research Ethics Committee of Jen-Ai Medical Foundation (111-09). This study was 
conducted in accordance with the Declaration of Helsinki. 
 
Experimental design in study 1  
    This study conducted a randomized crossover trial with a single-blind 
experimental design. All participants were subjected to two experimental conditions, 
one with CMR and a placebo trial (PL). The CMR was a colorless and odorless 6.4% 
maltodextrin solution, and mineral water was used for the PL. After at least two 
introductory sessions, the participants were randomly divided into two experimental 
sequences, CMR-PL or PL-CMR, by using a crossover design. The second phase of the 
experiment was held after 7 days of rest and recovery to eliminate the effects of muscle 
fatigue and delayed muscle soreness.  
 
 
Experimental design in study 2 
    This study conducted a randomized crossover trial with a single-blind 
experimental design. All participants were subjected to two experimental conditions, 
one with CAF and a placebo trial (PL). The CAF was chewing the caffeinated gum 
containing 200 mg for 20 minutes, and placebo gum was used for the PL. After at least 
two introductory sessions, the participants were randomly divided into two 
experimental sequences, CAF-PL or PL-CAF, by using a crossover design. The second 
phase of the experiment was held after 7 days of rest and recovery to eliminate the 
effects of muscle fatigue and delayed muscle soreness. 
 
Pretests 
    Two pretests were conducted before the formal experiment. The pretests involved 
familiarization with the experimental apparatus, practicing the movements, and testing 
with different inertia loads. The load resistance was 0.010, 0.025, 0.050, or 0.075 kg, 
and the participants’ peak power was used as the experimental load resistance. The 

pretests were separated by 7 days, and the first phase of the formal experiment and the 
last pretest were also separated by 7 days to allow for adequate recovery of muscle 
performance. 
The participants used an Exxentric inertial resistance training machine (Exxentric kbox 
4 Pro, Stockholm, Sweden) to complete the Romanian deadlift movement test. With the 
maximum inertial resistance measured during the pretest being used as the resistance 
load during the experiment, the participants underwent maximum inertial resistance 
training comprising five sets of five reps, with a 3-min rest between. 
 
The second pretest involved the same procedure as the first pretest but with the 
participants using the load resulting in the highest power output identified during the 
first pretest; the pretests were conducted at least 48 h apart. Before each test, the 
participants underwent a standardized warm-up supervised by the individual 
conducting the experiment, which included riding on a stationary bicycle with a 
speedometer for 5 minutes (at a manageable intensity, that is, in the 10–12 range on the 
perceived exertion scale, with the full range being 6–20), a joint range of motion warm-
up, and dynamic stretching for 3 min. Before the warm-up, the scale was explained.     
 
Formal experiment 
The participants were required to arrive at the laboratory at 3:30 p.m. on the day of the 
experiment, fast for at least 3 hours beforehand, and avoid high-intensity training (e.g., 
weight training, endurance training, and high-intensity interval training) for 3 days 
before the experiment. All groups were required to consume the same food 24 hours 
before the experiment and avoid caffeine, alcohol, energy drinks, and any form of 
stimulant or other substance that would affect exercise performance. 
Before the first experiment, the participants performed a standardized warm-up, 
comprising riding on a stationary bicycle for 5 minutes, joint range of motion warm-up 
and dynamic stretching for 3 min, and one set of eight reps of Romanian deadlifts with 
the flywheel; the load resistance was 0.01 kg. The participants rinsed their mouths with 
either 25 ml of CHO solution or the placebo solution for 20 seconds and spit the solution 
into a designated container after rinsing. Next, the participants used the inertial 
resistance training machine to complete the Romanian deadlift movement test. With the 
maximum inertial resistance measured during the pretest being used as the resistance 
load during the experiment, the participants completed maximum inertial resistance 
training comprising five sets of five reps, with a 3-min rest between. A 0.6-kg training 
bar was attached to the inertial resistance training machine during each testing session.  
To standardize the participants’ range of motion during testing, a piece of tape was 
placed at the midpoint between the tibial trochanter and talus to indicate the range of 

motion for the Romanian deadlifts, with the endpoint being full hip extension. The 
process was as follows: 
1. Participants stood over the tether with their feet hip-width apart, toes pointing 
forward, and head and eyes facing straight ahead. 
2. Hands were positioned shoulder-width apart, naturally lowered, with a positive grip 
on the training bar. 
3. The training bar was connected to the tether, which was connected to the flywheel 
shaft through a hole in the platform, and the movement began in the bent position (i.e., 
at the designated starting point of the range of motion). The participants pushed back 
on their gluteus maximus and kept their back straight, their shoulders pulled back, and 
their chest up. 
4. Each movement started with the concentric phase and ended with the eccentric phase. 
5. In the concentric movement phase, the crossbar was pulled along the thigh, and the 
tether was pulled to put the flywheel in motion. Participants contracted the gluteus 
maximus, hamstrings, and lower back muscles until the hip joint was fully extended to 
the end position. 
6. During the eccentric movement stage, the flywheel rotated, and the motion 
decelerated from the end position through centrifugal muscle contraction. Participants 
then completed the motion and returned to the starting position through a braking 
motion. 
7. These steps were repeated until the test was complete. 
8. The participants were instructed to not shrug their shoulders when their hip joints 
were fully extended and not allowed to flex their ankles.  
9. The participants began resisting the inertia in the first third of the concentric 
movement and then stopped moving at the end of the range of motion with maximum 
effort; the participants were instructed to perform the concentric movements quickly. 
    Before each set, participants performed one test movement to increase the power 
of the flywheel, followed by five test movements, and they were verbally encouraged 
throughout the test. These initiated the movement of the flywheel and increased its 
speed, and the resulting data were excluded from statistical analysis. In the second 
experiment, which was conducted 7 days later, the participants repeated the steps from 
the first experiment.  
    The participants’ test data were measured using Kmeter, fed back to the system, 
and transferred to an Android device (ASUS ZenFone 6) over Bluetooth for storage. 
The data were then exported to a computer in comma-separated value format for 
statistical analysis. The researchers analyzed data on seven factors measured using the 
Kmeter feedback system: power, concentric peak power, eccentric peak power, average 
force, average speed, peak speed, and total work.  

 
Carbohydrate solution and placebo 
    In the experiment, the carbohydrate solution was prepared by dissolving 6.4 g of 
colorless and odorless maltodextrin in 93.6 mL of water; the mixtures were then 
adjusted to a 6.4% maltodextrin solution for the participants to rinse their mouths; the 
placebo group rinsed their mouths with drinking water. All carbohydrate solutions were 
prepared by the principal investigator of the research project before the experiment, and 
they were similar to the placebo in appearance and taste to ensure that the participants 
could not distinguish them. Mouth rinsing was defined as distributing the carbohydrate 
solution around the mouth for a few seconds followed by spitting it out into a designated 
container. The most commonly used carbohydrate solutions are glucose and water-
soluble maltose dextrin at a 6.4% concentration(11), which are used for 15–20 seconds 
before exercise. Thirteen participants correctly guessed they were on carbohydrate 
(65%) and nine participants correctly guessed they were on placebo (45%). 
 
Caffeine gum 
The experimental group of caffeine gum will use the U.S. Army's caffeine gum 
(Military Energy Gum-StayAlert, Arctic Mint flavour; Chicago, IL) as the experimental 
group. Caffeine gum contains 100mg of caffeine. 
 
Exxentric kbox 4 Pro 
Many studies have described the mechanical advantages of flywheel devices and their 
effects on neurophysiological mechanisms, muscle morphological adaptation, and 
training during acute and chronic conditioning(12); this has stimulated an interest in the 
benefits of flywheel exercise in athletic training, injury prevention, and clinical 
rehabilitation among researchers and practitioners(13). 
    In inertial resistance training, flywheel inertia is used to generate eccentric force, 
enabling eccentric muscle training. The muscle groups that can be trained through this 
method include the triceps, biceps, gluteus maximus, quadriceps, back, and calves. Data 
on at least five factors (average power, concentric peak power, eccentric peak power, 
overload peak, and average force) can be measured using the Kmeter feedback system 
and presented as a bar graph in the app. The system can also be used to measure 
displacement distance, average speed, peak speed, total work (in joules), number of 
reps, and average rep time. 
 
Statistical analysis  
    The data are presented as means ± standard deviations, and the analysis was 
performed using SPSS (version 20, Chicago, IL, USA). The Shapiro–Wilk test was 

conducted to test the normality of the data. Paired-samples t-test was used to compare 
the average power, concentric peak power, eccentric peak power, average force, average 
speed, peak speed, and total work in the five Romanian deadlift sets between the CMR 
and PL groups. The before-and-after differences in heart rate and rating of perceived 
exertion (RPE) were analyzed using a repeated sample two-factor analysis of variance. 
Significance was α < 0.05. 
 
 
 
 

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