This cross-sectional study used data acquired from the 2014–2016 Korea National Health and Nutrition Examination Survey (KNHANES). This consists of a nutrition survey, a health interview survey, and a health examination survey and was devised in 1998 to estimate the health and nutritional status of the Korean population. The Korea Centers for Disease Control and Prevention (KCDC) conducted this nationally representative survey. A total of 5,437 female participants, older than 19 years, were included from the 2014–2016 KNHANES. We excluded women whose sedentary time and/or handgrip strength data were missing; who were pregnant; who had a history of cancer or chronic diseases, which could influence sedentary time, such as hepatitis B, hepatitis C, liver cirrhosis, chronic kidney disease, angina, myocardial infarction, asthma, thyroid disease, osteoarthritis and rheumatoid arthritis; or who had a limitation of physical activity due to any reason. Participants were divided in to three groups according to age.

During the 2014–2016 KNHANES, the participants were notified that their household has been randomly selected to participate voluntarily in a nationwide representative survey performed by the KCDC, and written informed consent was acquired from all participants. All citizens who agreed to participate had the right to withdraw at any time as per the National Statistics Law of Korea. The 2014–2016 KNHANES collected demographic, social, and health data of these participants. Covariates such as age, educational level, and household income were considered as socioeconomic factors. Health-related factors included alcohol intake, cigarette smoking, resistance exercise, and aerobic physical activity. Socioeconomic information was obtained from a health interview, while health-related behaviors were collected through a self-reported questionnaire. Current smoker was defined as current smoking status or those who had smoked more than 100 cigarettes during their lifetime. Alcohol intake was defined as more than 2–3 drinks per week based on queries on the participants’ average alcohol consumption frequency. Aerobic physical activity was measured according to the performance of aerobic activity as recommended by the WHO guidelines. Those who participated in at least 150 minutes or more of moderate-intensity activity per week or a combination of moderate- and high-intensity activity for 75 minutes or more per week were classified as “meets recommended guidelines”; all others were classified as “under recommended”. With regard to resistance exercise, participants were asked “How many days per week do you perform resistance exercises, such as push-ups, sit-ups, dumbbell exercises, weight lifting, and horizontal bar lifting?” The resistance exercise group consisted of subjects who performed resistance exercise 3 times or more per week. Trained medical staff performed the anthropometric measurements following a standardized procedure. Height and body weight were measured to the nearest 0.1 cm and 0.1 kg while participants wore light clothing without shoes. BMI was calculated as weight (kg) divided by the square of height (m²). Handgrip strength was measured using a digital hand dynamometer (Digital Grip Dynamometer, TKK 5401; Takei Scientific Instruments Co. Ltd, Tokyo, Japan) and was measured with the subject in a standing position with their arms fully extended at the sides, not touching the body. The participants were asked to exert maximum grip strength for <3 seconds, 3 times each with their left and right hands. At least 30 seconds of rest interval was allowed between each trial. Handgrip strength was defined as the maximally measured grip strength of the dominant hand.6) The overall daily sedentary time was estimated using the health interview survey, particularly the following question: “on average, how many hours per day do you sit down?” Responses were divided into three categories according to sedentary time: Q1, ≤5 h/d; Q2, 6–9 h/d; and Q3, ≥10 h/d considering the criteria of a previous study and population distribution in each age group [7].

Sampling weights were used to account for the complex survey design of the KNHANES; therefore, we obtained valid estimates that represented all Korean female adults and avoided biased estimates. The characteristics of the study participants were analyzed according to age and sedentary time using a weighted one-way analysis of variance for continuous variables and a weighted chi-square test for categorical variables.

The trend and relationship of handgrip strength and sedentary time (h/d) were calculated with a weighted analysis of covariance. All statistical analyses were performed using IBM SPSS statistical software ver. 23.0 (IBM Corp., Armonk, NY, USA). A P-value <0.05 was considered significant.