This study was approved by the ethical committee of the Technical University of Munich (Approval No. 584/20 S). Four trained and healthy males and females each (n = 8 in total) were recruited and completed the study (Table 1).
Table 1
Physical characteristics of participants. SD = Standard deviation
|
Male (n = 4)
|
Female (n = 4)
|
|
Mean ± SD
|
Range
|
Mean ± SD
|
Range
|
Age (year)
|
25.3 ± 3.6
|
22–30
|
23.8 ± 3.2
|
19–26
|
Height (cm)
|
187 ± 3.4
|
184–192
|
169 ± 12.5
|
152–182
|
Weight (kg)
|
82 ± 7.5
|
71–88
|
67.8 ± 6.2
|
62–76
|
The study had three study conditions:
-
no mask control,
-
commercially available surgical face mask (Fig. 1A) and a
-
taped filter mask (Fig. 1B)
The characteristics of the two face masks are described in Table 2. For taped masks, male participants used the larger size, whereas female participants used the smaller size.
Table 2
Physical characteristics of the masks
Mask Type
|
Size (cm)
|
Product name
- Materials
|
Weight
|
Thickness (mm)
|
Taped Mask
|
15 x 12
16 x 12.8
|
The Proper Mask
- Tape patch is comparable to KinesioTape (Suzhou MedSport Products Co., LTD.) and is combined with filter-fleece made of Premium-Protect® Filtration Layer FFP2 (Textilmacher GmbH; Munich, GER)
|
44 g/m2
|
0.46
|
Surgical Mask
|
17.5 x 9.5
|
Moon-Valley Face Mask
- Non-woven fabric (70%), Melt-blown fabric (30%)
|
3.5 g
|
0.4
|
Study protocol. All participants underwent a medical fitness examination at the start of the study to ensure they had no contraindication to exercise testing and to check for inclusion criteria. After passing medical screening, subjects participated in three graded cycling tests on three different days. Tests were at least 24 hours apart to ensure full recovery in-between tests. For each participant, all three tests were performed within a 2-hour time window to minimize influence due to circadian rhythms. For each testing session, participants performed a graded cycling test on a Lode Excalibur bicycle ergometer (Lode, B.V.; NL) until voluntary exhaustion. During these three tests, subjects either wore no mask (control), a surgical mask or a taped face mask. To avoid potential serial effects, the order of three mask conditions were randomized. The exercise protocol began at a workload intensity of 50 watts (W). After every 3 minutes, the load intensity increased by 25 W in a step manner. The test was terminated either during subjective exhaustion, when subjects withdrew voluntary, or until subjects reached level 10 on the dyspnoea scale or stable SpO2 < 80%. The measured parameters included perception of breathlessness, heart rate, SpO2 and blood lactate concentration.
Dyspnoea (shortness of breath) rating. Subjects were asked to rate the dyspnoea that they perceived at the end of each stage, using the modified Borg dyspnoea scale (35) (Table 3).
Table 3
Modified Borg dyspnoea scale (35)
Rating
|
Corresponding breathlessness intensity
|
0
|
No shortness of breath at all
|
0.5
|
Very, very light (barely perceptible)
|
1
|
Very light
|
2
|
Mild
|
3
|
Moderate
|
4
|
Rather severe
|
5
|
Severe
|
6
|
|
7
|
Very severe
|
8
|
|
9
|
Very, very severe
|
10
|
Maximal respiratory distress
|
Heart rate. Study participants wore a heart rate chest belt (Firstbeat Technologies Oy; FI) which continuously detects heart rate with a sampling frequency of 1 Hz throughout the graded exercise test. We used the Firstbeat SPORTS software tool (Version 4.7.3.1) to record the heart rate measurement. For the evaluation we determined the mean value of the detected signals of the last 30 seconds of each stage.
Oxygen saturation (SpO2) was measured by a pulse oximeter on a fingertip (Nonin 8000A, USA) with a sampling frequency of 5 Hz. We used the Lode Ergometry Manager software (version 10.6.0) to record oximeter data.
Lactate. To measure the metabolic response to exercise, 20 µl of capillary blood was taken from the earlobe of the subjects to determine the lactate levels. Blood was collected once at rest, at the end of each exercise stage, upon termination of the test, and at 1, 3, and 5 minutes after the end of the test. Subsequently, we determined the lactate values amperometrically using Biosen S Line device (EKF; GER). The lower detection limit of the instrument was a blood lactate concentration of 0.5 mmol/L.
Mask questionnaire. After completing the graded exercise test wearing a clinical mask or a tape mask, study participants provided feedback on their subjective well-being and evaluation of the masks during the test by answering a questionnaire. The content of the questionnaire was modified from the questionnaire that other studies used (23, 36) (Table 4). The questionnaire recorded subjective ratings and qualitative information about the comfort and wearability of the taped and surgical mask during the exercise test. Thereby the subjects could evaluate 11 questions on a visual analogue scale from 0 (totally disagree) to 10 (totally agree) and provide comments in an additional field.
Table 4
Content of the mask questionnaire. Adapted from (23, 36).
Question
|
Statement
|
1
|
The general condition of your daily form is very good today
|
2
|
The facemask prevents you from your maximal performance
|
3
|
The facemask fits very well
|
4
|
The wearing comfort of the facemask is very good
|
5
|
The facemask material feels very good on the skin
|
6
|
The sensation of moisture with the facemask is very low
|
7
|
The sense of smell with the facemask is very good
|
8
|
The feeling of tiredness occurs earlier with the facemask
|
9
|
Breathing is very difficult with the facemask
|
10
|
The heat generated with the facemask is very low
|
11
|
Suitable for intensive sporting activities
|
Statistics. For statistical evaluation, we used JASP software tool (version 0.12.0) to conduct the statistical analysis. As the duration of three exercise tests varied across conditions, for appropriate analysis of our exercise variables (perception of breathlessness, heart rate, blood lactate concentration and oxygen saturation) with a comparable exercise intensity, data was normalized, interpolated, and expressed in relative to individual peak power achieved (percentage of peak power) in the control condition. The exercise variables were assessed by one or two-way ANOVA for repeated measures to best answer our stated research questions. If there was a significant main effect, we used Bonferroni post-hoc tests for multiple comparisons.
To examine if there were differences between the ratings for surgical mask and taped mask from the mask questionnaire, paired t-tests were done to each domain of the questionnaire. For secondary analysis, we added gender as a between-group factor to evaluate if there was a gender difference in all analyses. Significance level was accepted as p < 0.05 for all statistical tests.