Effects of wearing a KF94 face mask on performance, perceptual parameters, and physiological responses during resistance exercise
Article information
Abstract
[Purpose]
Wearing face masks in indoor public places, including fitness centers, is an effective strategy for preventing the airborne transmission of viruses. Despite this, limited research has addressed the effects of wearing a mask during resistance exercise, which is primarily performed in indoor fitness centers. This study investigated the effects of wearing a KF94 face mask on exercise volume, perceptual parameters, and cardiorespiratory and cardiovascular responses during resistance exercise.
[Methods]
Twenty young men (23.8 ± 0.5 years old) participated in this randomized crossover trial. The participants performed moderate-intensity resistance exercise (60% of 1RM) sessions under two different conditions (KF94 mask vs. no mask). Cardiorespiratory parameters, exercise volume, rating of perceived exertion (RPE), and dyspnea were measured. Blood lactate concentration, blood pressure, arterial stiffness, and perceptual parameters were measured pre- and post-exercise.
[Results]
Wearing the KF94 mask significantly reduced exercise volume, ventilation volume, and ventilation efficiency compared to exercising without a mask (p < 0.05). Although blood lactate concentration remained unchanged between the two conditions, RPE and dyspnea were significantly higher with the KF94 mask (p < 0.01). Central arterial stiffness post-exercise was significantly higher with the KF94 mask than without it (p < 0.01).
[Conclusion]
Wearing a KF94 face mask during resistance exercise affected exercise volume, perceptual parameters, and cardiorespiratory and cardiovascular responses. These findings suggest that coaches and trainers should consider the individual characteristics when designing exercise prescriptions and modifying resistance exercise variables while wearing KF94 masks.
INTRODUCTION
The recent outbreak of coronavirus disease 2019 (COVID-19) has led to increased sedentary lifestyles and decreased physical activity, which, in turn, has increased the risk of cardiometabolic diseases, including sarcopenia and cardiovascular disease (CVD) [1-3]. Additionally, various symptoms, such as fatigue, dyspnea, functional mobility impairment, and muscle weakness due to COVID-19 may persist in both short and long term [4-6]. Specifically, impairment of physical function, including activities of daily living and functional mobility, may persist for up to six months after an acute infection [4].
Exercise is an effective non-pharmacological strategy for health promotion [7] and can mitigate negative consequences such as decreased physical function due to COVID-19 infection [8]. However, because exercise increases the volume of aerosols, the spread of virus-containing droplets during indoor exercise may be higher than that during rest [9]. While wearing a face mask can reduce the risk of airborne viral infection, it may also increase breathing resistance and lead to the re-inhalation of exhaled air, including carbon dioxide, potentially resulting in adverse physiological responses during exercise [10,11]. The physiological hypothesis suggests that inadequate gas exchange due to wearing face masks during exercise can lead to an acidic environment and cardiorespiratory stress [11]. Indeed, wearing surgical and FFP2 face masks during cardiopulmonary exercise tests can cause decreased cardiopulmonary function, such as minute ventilation (VE), via increased airflow resistance [12]. Furthermore, a recent study found that wearing an FFP2 face mask during vigorous-intensity aerobic exercise (77% HRmax) resulted in decreased capillary blood pH, increased capillary carbon dioxide partial pressure, and increased systolic blood pressure [13]. Additionally, a recent meta-analysis indicated that wearing face masks during exercise modestly affected perceptual parameters, such as subjective discomfort, as well as physiological parameters, including gas exchange and pulmonary function [14].
However, most previous studies have evaluated the psychological and physiological effects of wearing a face mask during aerobic exercise (walking, cycling, or running), and only a few studies have focused on wearing a mask during resistance exercise. Although a recent study reported that wearing an FFP2/N95 face mask during moderate-intensity resistance exercise (50% one-repetition maximum [1RM]) decreased oxygen saturation (SpO2) and increased the rate of perceived effort (RPE) [15], the effects of wearing a face mask during resistance exercise on physiological responses, including cardiorespiratory and cardiovascular parameters, remain largely unknown. Resistance exercise (or strength training) is primarily performed in indoor fitness centers, where the spread of the virus may increase. The popular fitness trend of resistance exercise is prominent according to not only the Southern Europe survey [16] but also the recent American College of Sports Medicine (ACSM) worldwide survey of fitness trends [17]. Therefore, it is necessary to clarify the perceptual and physiological responses to wearing face masks during resistance exercises.
This study aimed to investigate the effects of wearing a KF94 mask on exercise volume, perceptual parameters of effort and experience (e.g., RPE, dyspnea, and discomfort), and physiological responses (e.g., lactate, cardiorespiratory parameters, blood pressure, and arterial stiffness) during resistance exercise.
METHODS
Participants
Sample size calculation was performed using G*Power version 3.1.9.4 (Düsseldorf University, Düsseldorf, Germany). The total sample size for a paired t-test (two-tailed, d: 0.7, α error: 0.05, power: 0.8) indicated that 19 participants would be required. Twenty-two young men voluntarily participated in this study. To be included in this study, participants had to meet the following criteria: 1) aged 18–29 years; 2) determined healthy as evaluated by the Physical Activity Readiness Questionnaire (PAR-Q+); 3) nonsmokers; 4) physically active (>150 min/week of moderate intensity) as evaluated by the International Physical Activity Questionnaire (IPAQ); 5) autonomous (able to follow resistance exercise); and 6) experience of at least one year in resistance exercise. The exclusion criteria were as follows: 1) smokers; 2) inactive (<150 min/week of moderate intensity) as evaluated by the IPAQ; 3) those with claustrophobia, lung diseases, neurological diseases, musculoskeletal disorders, and cardiometabolic diseases, including metabolic syndrome and CVD; and 4) patients with a past medical history of diagnosed diseases. The study procedure was explained to all participants, who voluntarily signed informed consent forms before study initiation. Informed consent for the publication of identifying images in an open-access online publication was obtained from all participants. This study was approved by the Institutional Review Board of Incheon National University (permission# 7007971-202112-006A), and all experiments were conducted in accordance with the relevant guidelines and regulations.
Study design
This study used a randomized counterbalanced crossover design. All participants visited the laboratory thrice. The participants were randomly assigned to the KF94 mask or no mask condition using an online randomization tool (https://www.randomizer.org). Participants were asked to refrain from any moderate-to-vigorous physical activity, alcohol, and caffeine consumption for at least 24 h, sleep for at least 7 h, and maintain a fasted state for at least 10 h prior to all visits. All visits occurred in the morning (between 08:30 AM and 10:30 AM) under stable temperature (21–24°C) and humidity (40–50%) conditions to minimize the effect of circadian rhythm.
During the first visit, baseline clinical characteristics, including PAR-Q+, IPAQ, lipid and glucose profiles, body composition, and 1RM, were assessed for all participants. During the second and third visits, the participants performed moderate-intensity resistance exercise at 60% 1RM under two different conditions (with and without a face mask). In the mask condition, participants wore the same style of KF94 disposable face mask (19.1 × 10 cm, white color, four layers including non-woven polypropylene, elastic ear loops, three-fold sectioned 3D structure) during the resistance exercise. Cardiorespiratory parameters were continuously measured using the COSMED K5 portable metabolic system (Rome, Italy). Capillary blood samples (25 μl) were collected from the index finger in a seated position at two different time points (pre- and post-exercise), and blood lactate concentrations were measured using an Accutrend Plus (Mannheim, Germany), as described in a previous study [18]. Additionally, blood pressure and arterial stiffness were measured pre- and post-exercise. Perceptual parameters were assessed during resistance exercise and immediately post-exercise under two conditions. The outline of the study procedure is shown in Figure 1.
Diagram of the study design (A) and outline of the intervention (B).
Anthropometry and body composition
Height was measured to the nearest 0.1 cm using an extensometer (Samhwa, Seoul, South Korea). Body weight and composition were measured using an InBody 720 Scale (Biospace, Seoul, South Korea). Body mass index (BMI) was calculated using the formula: body weight (kg)/height2 (m2). During body composition measurements, the participants removed any metal materials and stood with bare hands and feet in contact with eight electrodes (two on the thumbs, two on the palms, two on the heels, and two on the toes).
Maximal strength (1RM testing)
1RM values of all participants were measured for back squats, conventional deadlifts, biceps curls, and bench presses. 1RM testing for all exercises was performed to determine the intensity of the resistance exercise protocol and assessed as an indirect estimation to ensure safety. Before 1RM testing, a warm-up was performed with dynamic stretching of the major muscle groups and resistance exercises with a light weight of approximately 10–20% weight load (barbell free of external load) of each participant’s body weight. Following the warm-up, the weight load for each attempt at 1RM testing progressively increased, with a maximum of eight repetitions and at least 3 min of rest between attempts. The highest lifted weight load and number of repetitions were recorded to estimate the 1RM, which was calculated as: weight × (1 + (0.033 × number of repetitions)) [19]. The resistance exercise intensity was set at 60% of 1RM, corresponding to moderate exercise intensity according to the ACSM guidelines [20].
Resistance exercise protocol
Previous studies have examined only one or two types of resistance exercises while wearing a face mask [15,21], but resistance exercises typically involve several exercises targeting major muscle groups, as recommended [20]. In this study, the resistance exercise protocol lasted approximately 50 min, consisting of a 5-min dynamic stretching warm-up, 40 min of main exercises (back squat, conventional deadlift, biceps curl, and bench press), and a 5-min dynamic stretching cool-down. The four main exercises were performed in four sets each, with approximately 1–2 s for concentric contractions, 1-s pause, and 1–2 s for eccentric contractions.
The participants performed a back squat in a self-selected foot stance, descending until their thighs were parallel to the ground. In the conventional deadlift, the participants maintained a grip width wider than their stance width and lifted the barbell while keeping their arms fully extended. The biceps curl was performed while standing with a straight barbell and lifting it toward the shoulders without flexing the humerus. For the bench press, the participants started with their elbows extending on a flat bench, moved the barbell to their chest, and returned to the starting position. The participants performed each exercise at 60% of 1RM, with 90 s of recovery between sets and 120 s of recovery between exercises, with 12 repetitions per set. If 12 repetitions were not possible, the participants performed the maximum possible number of repetitions. The repetitions were recorded at the end of each set, and the total exercise volume (sets × repetitions × load [kg]) was calculated.
Perceptual parameters
The RPE (Borg’s RPE Scale, scoring 6–20) and dyspnea (Modified Borg Dyspnea Scale, scoring 0–10) were measured at the end of each set. Subjective sensations, including humidity, heat, breath resistance, itchiness, tightness, saltiness, unfitness, odor, fatigue, and discomfort, were assessed using a scale measuring subjective perceptions (scoring 0–10) [22] in two different conditions post-exercise. The mean RPE and dyspnea across resistance exercises were recorded under both conditions.
Cardiorespiratory parameters
During the resistance exercise, heart rate (HR) was continuously measured using an HR monitor (HRM-Dual; Garmin Ltd, Schaffhausen, Switzerland) worn tightly on the chest. The oxygen uptake (VO2), VE, carbon dioxide production (VCO2), VE/VO2, VE/VCO2, respiratory frequency (RF), respiratory quotient (RQ), end-tidal oxygen partial pressure (PetO2), and end-tidal carbon dioxide partial pressure (PetCO2) were continuously measured breath-bybreath using the COSMED K5 portable metabolic analyzer. In the no mask condition, only the K5 mask was worn (Figure 2A1). In the KF94 mask condition, a KF94 mask was worn beneath the K5 mask (Figure 2B1) [23]. Air leakage was checked using maximal expiration force under both conditions (Figure 2A2 and B2) [10]. The fitting was carefully checked for air leakage due to lifting of the mask and lateral airflow. SpO2 was measured using a pulse oximeter (C101A2, Shanghai, China) on an index finger at the end of each set. The cardiorespiratory parameters for each set of resistance exercises were measured, and the mean values across the exercises were recorded for both conditions.
Fitting of the mask and air leakage test.
Fitting of the K5 COSMED mask without the KF94 mask (A1) and with the KF94 mask (B1). Respective air leakage tests of the K5 COSMED mask without the KF94 mask (A2) and with the KF94 mask (B2).
Arterial stiffness measurement
Participants rested in the supine position for at least 15 min before the arterial stiffness measurements were taken. The augmentation index (AIx) and carotid-femoral pulse wave velocity (cfPWV), both indicators of central arterial stiffness, were assessed non-invasively using the SphygmoCor XCEL system (AtCor Medical, Sydney, Australia), based on previously described methods [24,25]. Brachial artery pressure waveforms were recorded using a cuff placed on the right arm, which were automatically transformed into central aortic pressure waveforms using a validated mathematical transfer function. The AIx was estimated as the ratio of the augmented pressure to the central pulse pressure. The cfPWV was evaluated by recording the pulse waveforms of the carotid artery using applanation tonometry and those of the femoral artery using a cuff placed on the right leg. The cfPWV was calculated as the ratio of the distance between the measuring sites to the time of pulse waves moving between the sites. AIx and cfPWV were measured at least three times, and the average of two high-quality measures within ±0.3 m/s for cfPWV and ±3% for AIx was used.
After measuring the AIx and cfPWV, the brachial-ankle pulse wave velocity (baPWV), an index of peripheral arterial stiffness, was assessed as previously described26,27. Briefly, baPWV was measured noninvasively using the Omron Pulse Waveform Analyzer VP-1000 plus (Omron, Kyoto, Japan). The participants wore cuffs on both upper arms and ankles, and waveforms were collected from the brachial and posterior tibialis arteries. The baPWV was calculated as the ratio of the distance to the time of pulse waves moving between the two arteries, based on the participant’s height.
Statistical Analysis
All the analyses were performed using GraphPad Prism (version 9.0, GraphPad Software, USA). Variables are presented as the mean ± SEM, and the normality of distribution for variables was assessed using the Shapiro–Wilk test. A paired t-test was used to compare the exercise volume, SpO2, cardiorespiratory parameters, and subjective perceptions between the conditions (mask vs. no mask). The Wilcoxon test was used for variables that were not normally distributed. Two-way analysis of variance (ANOVA) with repeated measures was used to examine the condition (mask vs. no mask) × time (pre-exercise vs. post-ex-ercise) interaction effect on lactate, blood pressure, and arterial stiffness. Post-hoc analysis was performed using Bonferroni’s pairwise comparison. Statistical significance was set at p < 0.05.
RESULTS
Basic clinical characteristics of participants
Among the twenty-two participants, one withdrew due to schedule constraints, and another was excluded for not meeting the inclusion criteria due to a musculoskeletal disorder. Therefore, this study was finally conducted with twenty healthy and active young men. The participants’ characteristics are presented in Table 1. Participants had a mean age of 23.8 ± 0.5 years and weight of 75.4 ± 1.4 kg, height of 173.5 ± 1.1 cm, and BMI of 25.0 ± 0.3 kg/m2. Furthermore, participants had a mean back squat 1RM of 144.4 ± 5.6 kg, deadlift 1RM of 151.9 ± 5.7 kg, biceps curl 1RM of 41.4 ± 1.7, and bench press 1RM of 94.2 ± 3.2.
Basic clinical characteristics of study participants.
Exercise volume and lactate
All participants completed moderate-intensity (60% 1RM) resistance exercise sessions in at least 1-week intervals. Repetitions during the resistance exercise were significantly lower in the KF94 mask condition than in the no mask condition (p = 0.004; Figure 3A). Similarly, the exercise volume during resistance exercise was significantly lower in the KF94 mask condition than in the no mask condition (p = 0.002; Figure 3B). However, blood lactate concentration did not show significant differences between the conditions and interaction (condition × time) effects (p = 0.425; Figure 3C).
omparison between the two conditions on repetitions (A), exercise volume (B), and blood lactate concentration (C).
**p < 0.01; significantly different between the conditions. ***p < 0.001; significantly different from baseline. Values are shown as mean ± SEM.
Perceptual parameters
The RPE was significantly higher in the KF94 mask condition than in the no mask condition (p < 0.01; Figure 4A). Similarly, dyspnea was significantly higher in the KF94 mask condition than in the no mask condition (p < 0.001; Figure 4B). In addition, most subjective sensations (humidity, heat, breath resistance, tightness, saltiness, unfitness, fatigue, and discomfort) were significantly higher in the KF94 mask condition than in the no mask condition (p < 0.05; Figure 4C). Some subjective sensations, including itchiness and odor, did not show significant differences between the conditions (p > 0.05; Figure 4C).
Comparison of perceptual parameters including the rating of perceived exertion (A), dyspnea (B), and subjective sensations (C) between the two conditions.
*p < 0.05, **p < 0.01, and ***p < 0.001; significantly different between the conditions. Values are shown as mean ± SEM.
Cardiorespiratory parameters
VE, VO2, VCO2, RF, VE/VO2, and VE/VCO2 were significantly lower in the KF94 mask condition than in the no mask condition during resistance exercise (p < 0.001, p < 0.001, p < 0.001, p = 0.013, p = 0.012, and p < 0.001, respectively; Figure 5A–F). Additionally, PetO2 was significantly lower in the KF94 mask condition than in the no mask condition (p = 0.007; Figure 5G). Conversely, PetCO2 was significantly higher in the KF94 mask condition than in the no mask condition (p < 0.001; Figure 5H). The RQ did not show any significant differences between conditions (p > 0.05). Similarly, SpO2 and HR did not differ significantly between conditions (p > 0.05). Energy expenditure (kcal) was significantly lower in the KF94 mask condition than in the no mask condition during resistance exercise (p = 0.002; Figure 5I).
Comparison of cardiorespiratory responses including VE (A), VO2 (B), VCO2 (C), RF (D), VE/VO2 (E), VE/VCO2 (F), PetO2 (G), PetCO2 (H), and energy expenditure (I) between the two conditions during resistance exercise.
*p < 0.05, **p < 0.01, and ***p < 0.001; significantly different between the conditions. Values are shown as mean ± SEM. PetCO2, end-tidal carbon dioxide partial pressure; PetO2, end-tidal oxygen partial pressure; RF, respiratory frequency; VCO2, carbon dioxide production; VE, minute ventilation; VE/VCO2, VE to VCO2 ratio; VE/VO2, VE to VO2 ratio; VO2, oxygen uptake.
Arterial stiffness
At baseline, arterial stiffness indices, including AIx, AIx75@, cfPWV, and baPWV, did not differ between the conditions. There was a significant interaction (condition × time) for AIx, AIx75@, and cfPWV (p = 0.009, p = 0.011, and p = 0.012, respectively). Post-hoc analysis of AIx and AIx75@ was significantly higher post-exercise than pre-exercise in both conditions (p < 0.001; Figure 6A and B). Conversely, cfPWV was significantly higher post-exercise than pre-exercise in the KF94 mask condition (p = 0.0039) but not in the no mask condition (Figure 6C). Additionally, post-hoc analysis showed that AIx, AIx75@, and cfPWV were significantly higher post-exercise in the KF94 mask condition than in the no mask condition (p = 0.0055, p = 0.0095, and p = 0.0044, respectively; Figure 6A, B, and C). However, there was no significant interaction (condition × time) for baPWV (p = 0.1827; Figure 6D).
Comparison of arterial stiffness including AIx (A), AIx@75 (B), cfPWV (C), and baPWV (D) between the two conditions.
**p < 0.01, ***p < 0.001; significantly different from baseline. ##p < 0.01; significantly different between the conditions at post-exercise. AIx, augmentation index; AIx@75, augmentation index adjusted to heart rate at 75 beats/min; baPWV, brachialankle pulse wave velocity; cfPWV, carotid-femoral pulse wave velocity.
Blood pressure
Brachial systolic blood pressure (bSBP), brachial diastolic blood pressure (bDBP), central systolic blood pressure (cSBP), central diastolic blood pressure (cDBP), and central mean arterial pressure (cMAP) were measured pre- and post-exercise under both conditions. There were no significant interactions (condition × time) for bSBP, bDBP, cSBP, cDBP, and cMAP (p > 0.05). A comparison of blood pressure between the two conditions is shown in Table 2.
Comparison of blood pressure between the two conditions.
DISCUSSION
This study examined the effects of wearing a KF94 face mask on the exercise volume, perceptual parameters, and physiological responses during resistance exercise. To the best of our knowledge, this is the first study to investigate the physiological responses, particularly cardiorespiratory parameters and central arterial stiffness, to wearing a KF94 face mask during resistance exercises. The findings indicated that wearing a KF94 face mask during moderate-intensity resistance exercise significantly decreased exercise volume and increased the perceptual variables of effort and experience, including RPE, dyspnea, and discomfort. Additionally, significant differences in cardiorespiratory parameters and central arterial stiffness suggest that resistance exercise while wearing a KF94 face mask affects these physiological variables.
Wearing a KF94 mask during moderate-intensity resistance exercise was perceived to increase dyspnea and cause a subjectively uncomfortable feeling, including increased breath resistance and discomfort. Recent research has indicated that increased discomfort and dyspnea experienced when wearing a face mask during exercise can directly reduce exercise performance [23]. Increased RPE, dyspnea, and subjective sensations, including humidity, heat, breath resistance, tightness, saltiness, unfitness, fatigue, and discomfort, are likely to contribute to decreased exercise volume.
Furthermore, this study found that VE, VO2, and RF were significantly lower in the KF94 mask condition than in the no mask condition, likely because of the increased airflow resistance and decreased exercise volume. Similarly, a previous study showed that FFP2/N95 masks increased overall discomfort and decreased tidal volume (VT) and VE compared with the no mask condition during the incremental exertion test [10]. Additionally, in this study, wearing a KF94 mask during resistance exercise decreased VE/VO2 and VE/VCO2, indicating decreased ventilation efficiency [28]. Coaches and trainers should be cautious and consider modifying resistance exercise variables, including intensity, type, time, and frequency, while wearing a KF94 face mask. It is also necessary to consider the potential differences in the effect of the KF94 face mask on perceptual and physiological responses based on exercise type (aerobic vs. resistance) and intensity (low vs. moderate vs. high).
Intriguingly, in the present study, although exercise volume was reduced in the KF94 mask condition compared with the no mask condition, blood lactate concentration, which is elevated in an exercise intensity-dependent manner [18,29,30], did not differ between the two conditions after resistance exercise. A previous study showed that anaerobic running tests significantly increased blood lactate levels in the surgical mask condition compared with the no mask condition [31]. It has been proposed that inadequate O2 and CO2 exchange due to wearing face masks during exercise may induce an acidic environment and anaerobic metabolism [11]. Considering the findings of increased PetCO2, an indicator of the arterial blood partial pressure of CO2, and decreased VE, VO2, and PetO2 in the KF94 mask condition, despite decreased exercise volume, anaerobic lactate metabolism may be higher in the KF94 mask condition than in the no mask condition during resistance exercise.
Another finding of this study was that central arterial stiffness was higher in the KF94 mask condition than in the no mask condition after resistance exercise. Arterial stiffness is an independent marker for predicting future coronary heart disease [32,33]. The increased stiffness of the large elastic arteries can lead to increased systolic blood pressure and left ventricular load, potentially increasing the risk of CVD [34,35]. In this study, increased central arterial stiffness after resistance exercise while wearing the KF94 mask might have negatively affected cardiovascular function. Increased arterial stiffness is associated with impaired autonomic nervous function [36] and increased levels of cortisol, a biological marker of stress [37,38]. In particular, increases in cortisol concentrations can impair cholinergic vasodilation, which involves the inhibition of nitrite oxide synthesis [39]. The increase in central arterial stiffness under the KF94 mask condition may be due to activation of the sympathetic nervous system and elevated stress from increased discomfort, dyspnea, and RPE, even though the exercise volume decreased in the KF94 mask condition. However, because this study could not demonstrate the physiological mechanism, further research is required to investigate the related mechanisms in more detail, such as cortisol and nitrate/nitrite concentrations, autonomic nervous system function, and vascular endothelial function when wearing a KF94 mask during resistance exercise.
In contrast, central and brachial blood pressures and SpO2 did not differ between the two conditions after resistance exercise. These findings suggest that alterations in central arterial stiffness can occur independently of blood pressure. Similarly, a previous study showed that altered cfPWV after eight weeks of moderate-intensity aerobic exercise was independent of alterations in blood pressure, HR, or blood lipids, suggesting that the alteration of arterial stiffness after exercise was possibly due to direct vascular effects rather than secondary adaptations caused by alterations in traditional cardiovascular risk factors [40]. However, a previous study indicated that wearing an FFP2/N95 mask during vigorous aerobic exercise increased systolic blood pressure [13]. Another study showed that wearing an FFP2/N95 mask during moderate-intensity (50% 1RM) bench press resistance exercises decreased SpO2 [15]. These conflicting results may be due to differences in study protocols, such as exercise intensity (moderate vs. vigorous), type (aerobic vs. resistance and upper limb vs. both lower and upper limb exercises), and different face masks (FFP2/N95 vs. KF94). Therefore, additional studies are required to evaluate the effects of resistance exercise with a face mask, considering the exercise intensity and type, as well as the type of face mask.
Taken together, this study has several implications for resistance exercises using KF94 face masks. Resistance exercise with a KF94 mask reduced exercise volume and influenced not only perceptual parameters (e.g., increased RPE, dyspnea, and discomfort) but also physiological responses (e.g., decreased ventilation efficiency and increased Taken together, this study has several implications for resistance exercises using KF94 face masks. Resistance exercise with a KF94 mask reduced exercise volume and influenced not only perceptual parameters (e.g., increased RPE, dyspnea, and discomfort) but also physiological responses (e.g., decreased ventilation efficiency and increased
This study has several limitations. First, as this study included only active and healthy young men, the findings may not be generalizable to sedentary populations, older adults, or individuals with specific health conditions, such as respiratory disease and CVD. Second, while we investigated the perceptual and physiological responses to wearing a KF94 mask during resistance exercise, further research is needed to assess these responses with different types of face masks (e.g., surgical, cloth, and FFP2/N95). Third, although the fitting of the masks was checked for air leakage, some leakage may have occurred during the resistance exercise with the KF94 mask worn beneath the K5 mask. Finally, we measured cardiorespiratory parameters during resistance exercise and arterial stiffness pre- and post-exercise; however, future studies should explore physiological responses over longer durations of resistance exercise while wearing a face mask.
In conclusion, this study showed that moderate-intensity resistance exercise in the KF94 mask condition increased RPE, dyspnea, and discomfort and reduced exercise volume compared with the no mask condition; however, blood lactate concentration after resistance exercise did not differ between the two conditions. Furthermore, under the KF94 mask condition, ventilation volume and efficiency decreased during resistance exercise, whereas central arterial stiffness increased after resistance exercise. Therefore, it is necessary to design exercise prescriptions that consider personal characteristics and modify resistance exercise manipulation variables, including intensity, type, time, and frequency during resistance exercise using a KF94 face mask.
Acknowledgements
The authors thank Prof. Moon-Hyon Hwang for assistance with the operation of the SphygmoCor XCEL system. The authors declare no conflicts of interest.