The Effect of Caffeinate Chewing Gum on Ice Hockey Performance After Partial Sleep Deprivation: a Double-blind Crossover Trial
Phase: NA
Conditions: Caffeine, Placebo
Sponsor: National Taiwan Sport University

The effect of caffeinate chewing gum on ice hockey performance after partial sleep 
deprivation: a double-blind crossover trial 
 
Document Date: Aug 10, 2024 
 
Project summary 
The purpose of this study was to examine the impact of caffeinated chewing gum on 
the physical performance of elite ice hockey players in a partial sleep deprivation state. 
Fourteen national-level (Age: 25.2±5.4; height: 176.5±5.3; weight: 78.1±13.4) ice 
hockey players were tested late at late-night after a full day of partial sleep deprivation. 
A randomised, double-blind experimental design was employed in which participants 
either chewed caffeinated gum (CAF) containing 3 mg/kg caffeine or a caffeine-free 
placebo gum (PLA) for 10 minutes prior to undertaking a series of tests on-ice and off-
ice. The off-ice tests include a grip force, counter-movement jump (CMJ) and squat 
jump (SJ). The in-ice tests include 35 metre sprint, S-Shape agility test and Yo-Yo 
intermittent recovery test (Yo-Yo IR1 test). 
 
 
Introduction 
 
Ice hockey is one of the most popular sports in the world and has been an Olympic sport 
since 1920. Hockey is a high-intensity intermittent team sport. The players engage in 
periods of high-speed skating, interspersed with periods of passive recovery (1). It has 
been demonstrated that each skating session typically lasts between 30 and 80 seconds, 
with a subsequent recovery period of approximately 2 to 5 minutes. Similarly, for those 
engaged in ice hockey, it is essential to possess the requisite strength, agility, explosive 
power and aerobic endurance capacity (1). It can be argued that, in addition to their 
abilities on the ice, the physical capabilities of hockey players are also a significant 
factor in the sport. 
 
The influence of circadian rhythm on exercise performance has been demonstrated in 
numerous studies (2). In general, the optimal time for exercise performance is usually 
in the evening due to the higher core body temperature, which leads to increased energy 
metabolism, improved muscle compliance, and promotion of actin-myosin cross-
bridging (3). In accordance with the sleep model, the human circadian rhythm and the 
time since the previous period of rest both influence the characteristics of sleep(4). It 
can be reasonably deduced that modifying sleep schedules and circadian rhythm times 
may result in enhanced training quality. However, for athletes, student athletes, or when 

competing abroad, sleep schedules and circadian rhythms may be out of control. Prior 
to major competitions, 64% of athletes report partial sleep deprivation (5). It can be 
reasonably deduced that partial sleep deprivation may have an impact on physiological 
rhythms, which in turn may affect athletic performance. 
 
Caffeine is a beneficial nutrient that has been demonstrated to enhance athletic 
performance (6). It has been demonstrated that caffeine supplementation prior to 
exercise has a significant impact on improving endurance performance and reducing 
fatigue index in athletes. In sports requiring explosive power or agility, the effect size 
of caffeine was observed to be approximately small to moderate (7). In order to achieve 
a significant boost in pre-workout strength and explosiveness in explosive sports, a 
higher dosage of caffeine is required (8). However, supplementation with higher doses 
of caffeine may cause insomnia or affect sleep quality (9). One potential method for 
addressing insomnia may be to utilize smaller doses of caffeine prior to exercise, while 
still achieving a beneficial stimulant effect. 
 
Caffeine gum can be absorbed through the mucous membranes of the mouth, resulting 
in a faster absorption rate of caffeine (10), which may also have a higher effect size on 
athletic performance (11). Based on past literature, chewing smaller doses of caffeinate 
chewing gum has been found to improve lower body strength and explosive 
performance (12). It may be posited that the use of chewing gum as a caffeine 
supplement could prove an effective method of enhancing athletic performance without 
adversely affecting sleep quality. Caffeine supplementation can be effective in 
improving explosive power and vertical jump height during fatigue after partial sleep 
deprivation (9). However, there are no published studies investigating the impact of 
partial sleep deprivation on the physical performance of ice hockey players, whether 
on-ice or off-ice. The purpose of this study was to examine the impact of ingesting 
caffeinate chewing gum on the on-ice and off-ice athletic performance of hockey 
players experiencing partial sleep deprivation. 
 
Methods 
 
Experimental Design 
This study used a randomisation crossover design with a single-blind, double-blind 
experimental design. The participants were randomly assigned to either a caffeinated 
chewing gum trial (CAF) or a placebo trial (PL). After the first main trial, participants 
rested and recovered for 7-10 days before proceeding to the next trial. All participants 
completed all tests within one month. During the study period, all participants 

maintained their normal training status, with no changes in the training program, and 
no over-training or extra competitions. This is the out-of-season training period for 
players. 
    
 
Participants 
Fourteen trained ice hockey players (Age: 25.2±5.4; height: 176.5±5.3; weight: 
78.1±13.4) were recruited to participate in this study, including six defensemen, two 
centres, and six forwards. All participants had more than 6 years of professional hockey 
training and were familiar with all hockey skills. Inclusion criteria: 1. 6 years of 
professional ice hockey training, 2. 6 months of continuous training, 3. 3 months of 
recovery from sports injuries such as strains and sprains. Exclusion criteria: 1. non-
specialised ice hockey player. 2. has not trained regularly for the past 6 months. 3. has 
recovered from an athletic injury. 4. have been recovering from a sports injury for less 
than 3 months, or have epilepsy, hypertension, hyperlipidemia, heart disease, arthritis, 
osteoporosis, brain injury, or a history of caffeine allergy. In a past study, the effect of 
caffeinated chewing gum was found to have an effect size (Cohen's d) = 1.00 on the 
fatigue index of basketball players (11). The G*POWER statistical software (latest ver. 
3.1.9.7; Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany) indicated that 
eight participants were sufficient to interpret the data for the purposes of the study, with 
a power value of 0.8. In order to achieve a more precise POWER value, the number of 
participants in this study was set to 14. All participants provided written informed 
consent after being fully informed about the potential risks involved in the experiment, 
in accordance with the ethical standards of the relevant academic institution. A signed 
consent form was obtained from each participant. The order of participants was 
determined through the use of computerized randomization software (Excel Office 365). 
This study received approval from the Institutional Review Board of Jen-Ai Hospital - 
Dali Branch (202300071B0). All the data were performed at the indoor stadium. This 
study was conducted following the Declaration of Helsinki. 
 
 
Protocol 
All participants were required to perform the exercise-specific tests at least 2 times prior 
to the formal trial to familiarise themselves with the process of the formal trial. 
Participants were asked to record their diet 3 days before the first formal trial and were 
asked to repeat the same diet before the next trial. The following experiments were 
scheduled to start at 11 p.m. Upon arrival at the designated Ice hockey arena, the 
participants were granted a 10-minute rest.  

 
All participants remained awake (CAF: 11.5±2.2 hours; PL: 11.8±2.2 hours) for a full 
day after adequate sleep (CAF: 7.4±1.4 hours; PL: 7.1±1.2 hours), with no nap allowed 
in between. After 10 minutes of breath, participants chewed either caffeinate chewing 
gum (CAF) containing 3 mg/kg of caffeine or caffeine-free chewing gum (PL) for 10 
minutes each time. After spitting out the chewing gum, participants performed dynamic 
stretching and warm-up. After the warm-up, a 1-minute break was taken, followed by 
an off-ice test and an in-ice test. The measures employed in this study can be classified 
into two principal categories: off-ice tests and in-ice tests. In previous studies, a 
significant positive correlation has been identified between the off-ice tests and in-ice 
tests (13) Accordingly, the present study distinguished between off-ice and in-ice tests. 
The off-ice test includes grip force, counter-movement jump and squat jump (13). The 
in-ice test includes 35 metre sprint (13), S-Shape agility test (14) and Yo-Yo intermittent 
recovery test in ice (15). Participants were first tested on land, then after a 10-minute 
break and wearing ice equipment, they were tested on ice. 
 
Outcome measure 
The counter-movement jump was measured using Gymaware (GymAware, 
KineticPerformance, Australia). The device strap should be secured to the participant's 
waistband. The participant is instructed to remain as still as possible and place their 
hands on their waist. They are then required to squat down to the ground in a parallel 
position with their thighs, and then jump up as quickly as possible. The experimental 
procedure was conducted twice, with a one-minute interval between trials. The mean 
value of the two trials was calculated as the final result. 
 
The squat jump was measured using Gymaware. The device strap should be secured to 
the participant's waistband. The participant is instructed to remain as still as possible 
and place their hands on their waist. They are then required to squat down to the ground 
in a parallel position with their thighs for 2-3 seconds, and then jump up. The 
experimental procedure was conducted twice, with a one-minute interval between trials. 
The mean value of the two trials was calculated as the final result. The same vertical 
jump test has been employed in previous study (11). 
 
In the grip force test, the participant stood in a standing position holding a grip 
dynamometer (Smedlay's Hand Grip Dynamometer TTM, Japan) (16) with the grip 
adjusted to the second knuckle and the arm at about 10-15 degrees to the trunk, and 
continuously pressed the grip for about 3 seconds at maximum force. Both hands were 
tested twice with a one-minute rest in between. The average strength of both hands was 

taken as the result.  
 
The 35 metre sprint on ice (13) was measured using a timing grating (Witty, Microgate, 
Bolzano, Italy) with an accuracy of 0.01 seconds. The first timing grate was placed at 
the starting position and the second timing grate was placed at the 35m position. 
Participants dressed in official ice hockey equipment, ready to remain stationary, 
holding the stick and retreated behind the starting line, began to complete the 35-metre 
sprint with maximum effort, during the process of the stick close to the ice surface, each 
experiment performed twice, with a three-minute break in the middle of the experiment, 
to adopt the best results. 
 
The Ice S-Agility test is conducted using the timing grating (Witty, Microgate, Bolzano, 
Italy). The participant, wearing official hockey equipment and holding a stick, stands 
behind the half-ice goal and circles the two scrimmage circles in the half-ice, then 
sprints in a straight line across the blue line of the rink without touching the scrimmage 
circles and with the stick close to the ice surface. This approach has been used in the 
literature in the past (14). Each experiment was performed twice with a three-minute 
break and the best score was taken. 
 
The on-ice Yo-Yo IR test measures the aerobic endurance of hockey players (15). Place 
the cone at the start point, the finish point (20m), and the buffer zone (5m after the start 
point). Participants stand on the ice wearing official hockey equipment and holding a 
stick. A 20-metre sprint is performed after hearing an instruction tone, with a 10-second 
rest period after every 2 sprints. During the test, the indicator tone will speed up with 
the longer time, during the process, if two consecutive times can not reach the opposite 
cone before the indicator tone, it will be judged as a failure, and the results of the 
previous stage will be recorded. 
 
Caffeine and placebo gum 
The caffeinated chewing gum used in this study, specifically Military Energy Gum 
(Arctic Mint flavor; Stay Alert, Chicago, USA), has been previously utilized in other 
studies (12, 17). Each piece contained 100 mg of caffeine, with a 5 g gum base. The 
gum was provided in various weights, according to the relative dosage. A commercially 
available blue mint gum was used as the placebo. To achieve a target dose of 3 mg 
caffeine per kilogram of body weight and maintain a double-blind design, all chewing 
gums were mashed, ground, homogenised, and reshaped after incorporating 0.3 g of 
peppermint flavouring powder. This ensured that the colour, appearance, taste, weight, 
and size of the gum types were indistinguishable. All chewing gums were prepared by 

specialized individual and given to the on-site testers after numbering.  
 
Statistical Analysis 
All data are presented as means ± standard deviations. The normality of the data 
distribution was assessed using the Shapiro–Wilk test. The grip force, CMJ, SJ, 35 
metre sprint, S-Shape agility test and Yo-Yo intermittent recovery test were employed 
to analyses the through paired t-tests. The magnitude of the observed effects was 
quantified using Cohen's d, a measure of effect size. The power value of each data 
was conducted using G*Power 3.1.9.6 software (18). All data were calculated using 
SPSS (version 20, Chicago, IL, USA), and the significance level was p < 0.05. 
 
 
 

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