This study proposes an accelerometer-based method to objectively measure physical activity (PA) and leisure time physical activity (LTPA) in Chinese children accepting table tennis training in clubs.
An increasing body of evidence now shows that the majority of children in China experience lower levels of physical activity (PA) than the recommended guideline. Table tennis is a compound and technically difficult game that is popular in China; undertaking table tennis training in clubs can help children to elevate their levels of PA. Given that children cannot complete self-evaluated questionnaires themselves and caregiver-based observations are not suitable for children, we hypothesized that an actigraphy-based method can be an objective method to measure PA. In the present study, we describe a procedure that can be used to evaluate PA levels using an actigraphic device and software. Furthermore, since hip-worn devices are known to reduce compliance, we attempted to assess the agreement between hip-worn and wrist-worn device data. Collectively, our results indicate that these devices are suitable for measuring PA and leisure time physical activity (LTPA) levels. Together with subjective questionnaires, both hip-worn and wrist-worn devices are highly suitable for evaluating PA in Chinese children undergoing table tennis training in clubs.
Physical activity (PA) is very important in childhood and is positively associated with physical and mental health. It is well documented that PA is associated with beneficial effects in school-going children with regards to obesity, bone health, mental wellbeing, cognitive function, and academic achievements1,2,3. However, most children in China still experience lower levels of PA than recommended for their age4; furthermore, sedentary time is known to increase with age. According to the National Physical Fitness and Health Surveillance Study for Students in China, the number of students with obesity has remained significantly high over the first two decades of the 21st century5.
International PA guidelines for children and adolescents recommend at least 60 min of moderate-to-vigorous physical activity (MVPA) per day and vigorous physical activity (VPA) on 3 days/week6 in order to achieve health benefits. Similarly, the latest version of the Physical Activity Guidelines for Chinese (2021)7 highlights that accumulated sedentary behavioral time should not last for more than 60 min, based on international PA guidelines. Participation in sports clubs or school activities is a highly beneficial way by which children can meet PA guidelines8. Table tennis is a compound and technically difficult game that is popular in China. Recent studies have confirmed that regular table tennis training has a positive effect on the health-related physical fitness of children and adolescents9,10. As such, table tennis club/school-based training is a very suitable method for children to increase their levels of PA11.
It is important to consider several issues that might impede the fulfillment of the recommendations made by international PA guidelines. For example, most surveys of PA in children are based on parent-reported questionnaires12; there is a significant lack of data acquired by objective methods in China. Furthermore, the activity patterns of children are characterized by relatively short bouts of spontaneous, but intense PA13,14. This type of pattern is difficult to summarize and report by observation alone; additionally, questionnaires or parental reports are prone to error15. Secondly, children spend a significant amount of leisure time at home, for example, during the evenings and weekends, and tend to accumulate a substantial part of their daily PA in a home-based setting. It is difficult to collect or estimate leisure time physical activity (LTPA) in children outside of school hours. LTPA is essential for health and is one of the most important components of total PA16. Thirdly, the PA of children may be influenced by gender differences and parental life style8. Collectively, this information highlights the need to acquire accurate measurements of PA to evaluate overall health, its social impact, and its use in policy making. If the activity levels of specific subpopulations (e.g., children undergoing table tennis training) are not correctly estimated, it is possible that the data may even misdirect policies and public health priorities12.
As the most widely used objective measurement for PA patterns in youths, accelerometers have been recognized as the gold standard for measuring PA in children17,18,19,20. With technological improvements, actigraphic devices have progressed into cost-effective capacitive sensors. In most cases, these devices need to be attached to the right hip21, an issue that might be a potential risk factor and lowers compliance22. Over recent years, several research studies have indicated that PA data derived from devices worn at other anatomical locations can be comparable when set-up appropriately23,24.
In the present study, we aimed to develop a wrist-worn actigraphy accelerometer-based method to assess PA in children undergoing table tennis training.
This study was approved by the Academic Ethics Committee of Inner Mongolia Medical University in Hohhot, China. The parents of all children included in this study provided signed and informed consent. In the study, we used the Actigraph GT3X+ device which is referred to as an accelerometer hereafter.
1. General aspects of method development
2. Initialization of data collection using the accelerometer
3. Data collection from diary entries
4. Accelerometer data output
5. Scoring the data
6. Statistical analysis
Demographic data are shown in Table 1, including gender, age, height, weight, ethnicity, and dominant hand. As shown in Table 1, there were no significant differences between the groups with regards to gender, age, height, weight, and dominant hand. Furthermore, participants from the Sports group did not exhibit any significantly different parameters in terms of sedentary behaviors (SB; 441.05 ± 31.80 vs 442.25 ± 30.74, P = 0.904), LPA (213.10 ± 15.00 vs 215.65 ± 17.41, P = 0.623), MPA (42.55 ± 3.80 vs 40.70 ± 2.85, P = 0.090), as well as LTPA (1514.20 ± 146.10 vs 1587.70 ± 182.25, P = 0.167). In contrast, children in the Sports group exhibited a significantly higher VPA (21.65 ± 3.43 vs 17.15 ± 4.01, P = 0.0001) and MVPA (64.20 ± 2.33 vs 57.85 ± 3.36, P < 0.001) than those in the Control group.
The Bland-Altman plot was originally developed to compare data with two sets of measurements on one occasion. It was expected that 95% of the differences between the two measurement methods would fall within the 95% limit of agreement. As shown in Figure 3, Bland-Altman plots suggested that the agreement between hip-worn and wrist-worn accelerometer data was acceptable for MPA, VPA, and MVPA. There were two (10%), zero (0%), and three (15%) outliers from the 1.96 standard deviation value for MPA, VPA, and MVPA, respectively.
Figure 1: Vector magnitude counts (raw data) depicted as plots. The graphs on the left show the vector magnitude counts per day. The table on the right provides the exact vector magnitude count for each epoch (60 s). Four graphs for VM are magnified and shown at the bottom. Please click here to view a larger version of this figure.
Figure 2: The scoring page shown in the device software. The Puyau Children (2002) options for Cut Points and MVPA are accessible in the Algorithms section on the left. Scoring output can be obtained automatically by clicking the Calculate and Export buttons. Please click here to view a larger version of this figure.
Figure 3: Bland-Altman plot for physical activities using hip-worn and wrist-worn actigraphic devices. (A) Bland-Altman plot for MPA using hip-worn and wrist-worn actigraphic devices. (B) Bland-Altman plot for VPA using hip-worn and wrist-worn actigraphic devices. (C) Bland-Altman plot for MVPA using hip-worn and wrist-worn actigraphic devices. Please click here to view a larger version of this figure.
Sports group | Control group | P value | |
Gender (male/female) | 10 male/ 10 female | 8 male/ 12 femal | 0.537 |
Age (years) | 9.85±1.34 | 9.80±1.36 | 0.908 |
Height (cm) | 135.3±9.41 | 135.8±9.43 | 0.881 |
Weight (kg) | 36.65±7.25 | 35.10±4.84 | 0.432 |
Dominant hand (right%) | 15% | 10% | 0.643 |
SBs (minutes) | 441.05±31.80 | 442.25±30.74 | 0.904 |
LPA (minutes) | 213.10±15.00 | 215.65±17.41 | 0.623 |
MPA (minutes) | 42.55±3.80 | 40.70±2.85 | 0.090 |
VPA (minutes) | 21.65±3.43 | 17.15±4.01 | 0.001 |
MVPA (minutes) | 64.20±2.33 | 57.85±3.36 | <0.000 |
LTPA (VM counts/) | 1514.20±146.10 | 1587.70±182.25 | 0.167 |
Table 1: Demographic and actigraphic data. The table provides the demographic and actigraphic data collected from the Sports group and the Control group. Abbreviations:cm = centimeters; kg = kilograms; SBs = sedentary behaviors; LPA = light physical activity; MPA = moderate physical activity; VPA = vigorous physical activity; MVPA = moderate-to-vigorous physical activity; LTPA = leisure time physical activity; VM = vector magnitude.
As shown in Table 1, children in the Sports group exhibited a significantly higher VPA and MVPA (64.20 ± 2.33 vs 57.85 ± 3.36, P < 0.001) relative to those in the Control group. According to the findings of previous reports in both adolescents25 and young adults26, accelerometer devices represent an accurate method for the estimation of PA, relative to subjective surveys.
Bland-Altman plots demonstrated that there were high levels of agreement for MPA, VPA, and MVPA between hip-worn and wrist-worn accelerometer data (shown in Figure 3). This result indicated that these devices can also be worn on the wrist to assess PA. However, we must highlight that the agreement between hip-worn and wrist-worn accelerometer data for MPA was lower than that of VPA. This is because in low strength PA, such as sitting in the classroom or doing homework, the hip-worn accelerometer graph mainly reflects the movement of the body's center of gravity, while the wrist-worn accelerometer graph mainly reflects the movement of the non-dominant upper extremity. In addition, considering the different levels of compliance between hip-worn and wrist-worn devices, it is important to select the most appropriate device to evaluate PA in children undergoing table tennis training in clubs.
The critical steps in the protocol are to confirm the availability of the raw VM count data and the accelerometer data for LTPA. In other words, the main challenge will be to ensure that the data undergo quality control in a strict manner. It is highly recommended to use data plotting to monitor the data from each participant. Periods in which the device was not worn can be identified as long strings of zero counts and must be removed from the final dataset, even if the participants do not report this period as a time when they were not wearing the device. Leisure time and sleep diaries are useful for identifying LTPA; consequently, it is necessary that the parents or caregivers acknowledge their children's daily information in a precise manner.
The software used by the accelerometer contains several algorithms that are suitable for children, including the Puyau Children (2002) algorithm, the Freedson Children (2005) algorithm, and the Mattock Children (2007) algorithm. The Everson Children (2008) algorithm was previously chosen to evaluate the PA of children and adolescents in Tibet27, while the Pate Preschool (2006) algorithm was chosen to evaluate PA in preschoolers residing in Shanghai, China28. In our present study, we used the Puyau Children (2002) algorithm because it is the most useful method with which to classify children according to body mass index and fat mass percentage29.
In addition, we needed to elucidate the exact equations to use; this was determined by the specific type of accelerometer device used to acquire the raw data (see the equation below).
VM =
In the equation, X, Y, and Z are the vector magnitude counts for the X-axis, Y-axis, and Z-axis, respectively. LTPA represents the average PA during leisure time.
The triaxial VM counts per minute cut-off for different PA intensities were determined by the Puyau Children (2002) algorithm, as follows: sedentary behaviors <799; light PA = 800 to 3199; moderate PA = 3200 to 8199; vigor PA >8200; and moderate and vigor PA >3200. In future, different types of algorithms will be modified to provide an optimized algorithm for the specific characteristics of subjects.
The accelerometer device has three main limitations that need to be considered. First, the hip-worn method is thought to be the best choice for reflecting PA; however, this method shows poorer compliance relative to wrist-worn devices, especially for young children30. Second, the complexity and high price of the device (including software) can impede the utility of the accelerometer device and software in a home environment. Otherwise, clinical staff, institutional researchers, and sports-club coaches can easily manage this method, and the associated cost will decrease if the device is widely reused. Third, accelerometer devices only have a basic waterproof guarantee; thus, these devices should not be used for some sports participants, such as those undertaking sailing, rowing, and swimming.
There are some alternative methods that could be used instead of accelerometers. For example, many cell phones have similar functions for measuring PA, albeit with relatively low reliability and validity. Other studies have reported more cost-effective pedometers that are suitable for individuals31. Further research needs to identify the reliability and validity of all alternative methods.
Collectively, our results indicate that both hip-worn and wrist-worn accelerometers can effectively measure PA and are highly suitable for Chinese children undertaking table tennis training in clubs. These methods also can be used to evaluate PA in both healthy individuals and children with developmental disorders such as cerebral palsy32, autism33, and ADHD34.
The device used here is considered as the gold standard for measuring PA, as mentioned earlier. However, preliminary reports suggest that these devices can also measure sleep quality, circadian rhythm, and rest-activity rhythm in clinical practice35,36. Further investigations are now needed to widen the scope and application of these devices. These devices can also be helpful in monitoring PA in children undertaking table tennis training in clubs. Together with subjective questionnaires, such as the Health Behavior in School-aged Children Questionnaire and the International Physical Activity Questionnaire, this method is capable of demonstrating the PA of children in a highly effective manner.
The authors have nothing to disclose.
We thank Ms Shuo Tian for the digital technology support. This study was supported by the Wu Jieping Foundation (Grant No. 320.6750.18456).
Actigraph | ActiGraph Corp | GT3X+ | device |
ActiLife | ActiGraph Corp | v6.13.3 | software |
SPSS 22.0 software | statistical analysis software |