Introduction
Coronavirus disease-19 (COVID-19) is a respiratory illness characterized by fever, cough, and fatigue, and it initiated a global pandemic in January 2020 [1]. In contrast to other viral infections, COVID-19 is highly contagious, lethal, and spreads from person to person, especially through droplets [1,2]. In addition, COVID-19 has a long incubation period of up to 2 weeks [2]. Due to these features, most countries came up with policies such as lockdowns or social distancing to minimize human-to-human contact, which included limited outdoor activities [3].
Reduced physical activity levels due to lockdown or social distancing during COVID-19 can negatively affect body composition and muscular function [3]. During the pandemic, physical activity participation markedly decreased with an increase in waist circumference and body mass index (BMI) in South Korean adults; moreover, metabolic syndrome prevalence significantly increased [4-6]. Women especially showed a more pronounced decline in physical activity time during the pandemic [6].
To buffer the negative effects of lockdown-associated physical inactivity, home-based resistance exercises (i.e., weight-bearing exercises), such as push-ups and squats, could be recommended [3]. Furthermore, according to progress in digital streaming technology, home-based exercise utilizing an online platform received worldwide attention in 2021 [7]. Recently, online exercise programs showed a high level of adherence and improved physical fitness [8]. During a pandemic, online exercise can be a suitable alternative to increase physical activity.
However, established online exercise programs have some limitations, including the use of recorded video and a lack of supervision from trainers [8,9]. Moreover, these limitations can be a barrier to participating in online exercise programs for beginners or those who are not familiar with exercise [9]. Therefore, this study aimed to determine the effectiveness of online and non-face-to-face exercise programs on body composition and muscular function in physically inactive women during the pandemic.
Methods
Participants
The study participants were recruited between November and December 2020, including individuals who had no restrictions on daily physical activity and exercise and who had not engaged in regular exercise for the previous 3 months. Individuals with musculoskeletal or neurological disorders or pregnancy conditions were also excluded. In addition, we excluded participants who contracted COVID-19 during the intervention period. The study included 23 participants; however, two did not complete the exercise program for personal reasons. Finally, we analyzed 21 participants (21 women, mean age: 40.57 years) who were physically inactive (Table 1).
Written informed consent was obtained from all participants. This study was approved by the Institutional Review Board of the Korea Maritime and Ocean University (No. KMOU IRB 2020-04) and registered on the Korea National Clinical Research Information Service (CRIS; No. KCT008942), a World Health Organization International Clinical Trials Registration Platform.
Study design
This single-arm trial study included twenty-two participants who performed the same exercise program (weight-bearing exercises). We utilized an online communication platform (ZOOM, Zoom Video Communication Inc., California, USA) to perform the non-face-to-face intervention during the COVID-19 pandemic. All procedures, including the pre- and post-test, were conducted in compliance with COVID-19 precautions outlined by the Korea Disease Control and Prevention Agency [10].
Exercise program
For 10 weeks, each participant engaged in the exercise program three times a week, resulting in a total of 30 sessions per participant. The online exercise program was available at three different times throughout the day (10 AM, 4 PM, and 8 PM), allowing participants to complete the programs. The exercise program consisted of six weight-bearing resistance exercises for 30 min, including a warm-up (5 min) and cool-down (5 min) period with dynamic stretching. To apply the progressive intensity, we divided the exercise program into three phases: adaptation-, 1st progress-, and 2nd progress weeks (Figure 1). We utilized the Borg 6–20 scale to evaluate the exercise intensity at each phase [11]. Additionally, we assessed the rating of perceived exertion (RPE) after the first session of each week to confirm the prescribed intensity was maintained. The instructor advised the participants to reduce the number of repetitions for each exercise if their reported RPE exceeded the prescribed intensity. At the beginning of each phase, the instructor demonstrated the initial set of each exercise, offering guidance for proper motion. The participants proceeded to replicate these exercises while the researcher carefully observed and advised the participants’ motion in subsequent sets. The instructor supervised all sessions of the exercise program. We required participants to engage in the exercise program with a minimum 24-h interval between sessions and encouraged them to attend the next session within 48 h to ensure regular exercise. The average attendance rate for the exercise program was 97.6 ± 4.6%.
Measurements
When the participants visited the laboratory, we first requested them to fill out the International Physical Activity Questionnaire to determine their level of physical activity and sedentary time for a day or a week. To assess muscular function, we evaluated the isokinetic peak torque of the knee joint, as well as lower limb proprioception. Measurements were taken in the following order: 1) body composition measurements, 2) proprioception measurements, and 3) muscular function measurements.
1) Body composition
Body composition was measured by bioelectrical impedance analysis (BIA) and a computed tomography (CT) scan. We measured body weight (kg), fat mass (kg), fat percentage (%), BMI (kg/m2), lean body mass (kg), muscle mass (kg), skeletal muscle mass (kg), and skeletal muscle index (kg/m2) using the Inbody 470 (Inbody, Seoul, Korea), which utilizes the BIA method. The cross-sectional area of visceral fat (cm2) and thigh muscles (cm2) was measured using the gold standard method, the HITACHI CT scanner (HITACHI, Tokyo, Japan) [12]. We calculated the area of the thigh muscles by averaging the sum of the bilateral thigh muscle area.
2) Lower limb proprioception
We assessed lower limb proprioception using two proprioception types: joint position sense (°) at two levels (30° and 60°) and force sense (Nm) at 20% and 50% of maximum voluntary isometric contraction (MVIC) [13,14]. Participants were seated on a chair of Biodex System 3 (Biodex Medical System Inc., New York, USA) and were required to keep the knee flexion at 90°. First, the experimenter passively moved the participant’s dominant leg at 30° to allow the participant to memorize the target level. The participant returned the leg to its initial position after the familiarization trial. The participant attempted to move the leg at the target angle with closed eyes to eliminate visual cues, followed by a 5-s interval. We measured the MVIC at 45° of knee extension to assess the force sense in the knee joint [14]. Similar to the joint position sense test, participants performed a familiarization trial with visual feedback using a bar graph to reach the target force on the monitor. After finishing the familiarization trial, participants were asked to reproduce the target force in 5 s.
3) Muscular function
We evaluated lower body muscular functions by measuring the isokinetic peak torque of the knee joint at three angular velocities (60°/s, 90°/s, and 180°/s) using a Biodex System 3. All participants responded regarding their dominant leg before the measurements (right leg, n=21). We recorded the highest value for analysis after the participants performed five repetitions of extension (Nm) and flexion (Nm) in the knee joint. Similarly, we calculated and presented the relative values (Nm/kg) of lower limb strength and power. Angular velocities of 60°/s and 180°/s were suitable for measurement of lower limb strength and power [15]. A velocity of 90°/s could be considered a compositive variable for strength and power.
Statistical analysis
We performed the Shapiro-Wilk test to assess the normality of body composition and muscular function variables. In addition, we conducted a non-parametric test (Wilcoxon-signed rank test) for body composition (cross-sectional area of visceral fat and thigh muscles), which did not meet normality tests. For other variables of body composition, isokinetic peak torques (flexion and extension) at three angular velocities (60°/s, 90°/s, and 180°/s), and lower limb proprioception that did meet normality tests, we performed a parametric test (paired t-test) and presented the effect size according to Cohen’s d method. SPSS version 29.0 (IBM, New York, USA) was used for statistical analysis, and the level of statistical significance was set at p<0.05.
Results
After 10 weeks of an online- and home-based exercise program, BMI significantly decreased; in addition, other variables of body composition showed no changes. Visceral fat area significantly decreased (77.11 ± 34.54 cm2 vs. 74.70 ± 31.08 cm2; p=0.03), and thigh muscles increased (97.92 ± 15.87 cm2 vs. 99.83 ± 16.31 cm2; p=0.001).
Lower body strength (60°/s) (flexion: +13.7% and extension: +9.2%) and power (180°/s) (flexion: +12.3% and extension: +12%) increased. These results were significantly higher even after considering body weight (p<0.001, Table 3).
Mean differences from 30° and 60° decreased significantly (30°: 4.25° vs. 2.46°, p=0.002; 60°: 3.51° vs. 2.13°, p=0.003), and force differences from 20% and 50% MVIC also decreased (20% MVIC: 25.06 Nm vs. 14.50 Nm, p=0.004; 50% MVIC: 14.53 Nm vs. 9.74 Nm, p=0.04).
Discussion
Our results showed that online-based exercise significantly improved body composition and muscular function, including isokinetic peak torques and lower limb proprioception, in physically inactive women. Staying active has become even more important since the COVID-19 outbreak [6,16-18]. Reduced physical activity and increased sedentary time due to the pandemic can contribute to a decline in muscular fitness (strength and power) and have been reported to contribute to several health problems [17,19-21]. Therefore, numerous exercise experts suggest using online and home-based exercise to counteract the decline in physical fitness resulting from the COVID-19 lockdown [19,20]. In addition, there is a growing necessity for safer programs to counteract the pandemic-associated decline in physical activity [6,16]. In this regard, our findings may support the importance of an online-based and non-face-to-face exercise program to maintain physical activity and improve muscular function.
Increased BMI and visceral fat are significantly associated with several metabolic diseases [22,23]. In particular, visceral fat levels are considered an important variable in interventions to improve metabolic risk factors [23]. During the COVID-19 pandemic, the prevalence of abdominal obesity, closely associated with visceral fat accumulation, increased by approximately 3.3% [18]. Moreover, a high level of visceral fat has been reported to be strongly associated with COVID-19 severity [24]. Therefore, effective strategies are needed to manage the visceral fat level during a pandemic. Resistance exercise has been reported to be an exercise form that can manage visceral fat independent of caloric restriction [25]. The present study reported significant reductions of 1.3% and 3.1% in BMI and visceral fat, respectively, without caloric restriction. However, 8 weeks of dietary intervention and high-intensity interval training showed a significant decrease of 13% and 33% in BMI and visceral fat, respectively, in women with abdominal obesity [26]. Although online-based and non-face-to-face exercises can be effective for managing BMI and visceral fat levels, the effects of dietary interventions or calorie restriction cannot be ignored for greater changes in body composition [27]. Therefore, future studies will be needed to determine the synergetic effects of dietary control and an online-based exercise program on body composition.
A decrease in thigh muscle mass and strength primarily affects the decline in lower limb muscle function with aging [28,29], which has been significantly associated with deterioration in daily living activities and gait performance [30]. Furthermore, proprioceptive impairments, along with a decrease in muscular function, are among the factors that increase the risk of falls in older adults [31]. Despite the lockdown, our results showed that the online exercise program produced significant increases in cross-sectional area (+2%), strength (+9%), and power (+12%) in thigh muscles. Similar to our results, 8 weeks of online-based and weight-bearing exercise significantly improved muscular fitness in older adults [32]. Additionally, the present study showed significantly improved lower limb proprioception, including joint position (+39–42%) and force (+33–42%) senses. These changes in muscular function and proprioception derived from online-based exercise can contribute to increased gait performance and reduced fall risks [28,31]. Considering that women are more susceptible to disuse-induced muscle wasting (i.e., muscle loss caused by a physically inactive lifestyle) [33,34] and a significant decrease in physical activity levels compared with men regardless of the pandemic [6,21], our results and those of previous studies support the importance of online-based resistance exercise to preserve muscular function.
Our study has some limitations. First, based on the study’s single-arm intervention design, we could not compare it to a face-to-face exercise intervention with the same program. Therefore, further studies are needed to verify the clear effects of online-based exercise by comparing it with face-to-face exercise programs. Second, our study only included physically inactive females. Prior to the pandemic, patients and older individuals were typically provided online exercise programs; however, given the increased use of online and home-based exercise since the pandemic, follow-up studies with a wider range of ages, sexes, and exercise levels are necessary.
Conclusion
Our data suggests that online-based and non-face-to-face exercises proved effective in improving body composition, including fat loss, muscle gain, and improved muscular function in physically inactive women during the COVID-19 pandemic. Online and non-face-to-face exercises have time and space advantages. In addition, technological developments that make it more convenient to interact in real-time with the trainer and/or supervisor can increase access to online exercise. Consequently, online exercise can be a suitable alternative to improve body composition and muscular function for physically inactive individuals, even post-pandemic.
PDF Links
PubReader
ePub Link
XML Download
Full text via DOI
Download Citation
Print
