A study in China found that mental disorder symptoms were less frequent among physically strong adolescents, those with high muscular strength, compared to adolescents with low muscular strength. The association between better mental health and higher physical strength was stronger in males than in females. The study was published in PeerJ.
Mens sana in corpore sano (“a healthy spirit in a healthy body”), an ancient Roman proverb, pretty well depicts how many cultures across the globe see the relationship between mental and physical condition of a person. When we look at adolescents and children, studies have shown that their muscle strength can predict a variety of health outcomes, including risk of death from all causes, cardiovascular disease, and also psychological health.
Adolescence is a stage of life when profound individual, biological, and social changes take place. Their physical strength develops rapidly, but adolescents are also prone to different psychological symptoms, such as self-harming behaviors, hostility, anxiety, and depression. Studies show that 10-20% of teenagers exhibit at least one of these adverse psychological symptoms. These are, on the other hand, still much lower percentages than those of adults, where often more than 50% of people are or can be diagnosed with some mental illness.
Following up on previous research that indicated there might be an association between physical, muscle strength, and mental health, Jinkui Lu and his colleagues conducted a study that involved 14,344 adolescents from eight cities in different regions of China between April and July 2018. Four middle schools were selected from each region for participation in the study and, within each school, two classes were randomly selected from each grade. Numbers of boys and girls was roughly equal — 7,180 boys and 7,164 girls, all between 13 and 18 years of age.
All study participants completed a muscle strength test that consisted of three items: a grip test to measure upper limb strength, sit-ups to measure torso strength and a standing long jump to measure lower limb strength. For comparison purposes, researchers selected the 25% of the strongest students and 25% of the students with lowest strength results. Participants also completed a survey of psychological symptoms (the Multidimensional sub-health Questionnaire of Adolescents, MSQA).
Results showed that 21.4% of the studied adolescents had at least one adverse psychological symptom. Emotional and behavioral symptoms were more common than social adaptation difficulties. Symptoms were a bit more often detected in males (22.1%) than in females (20.7%).
Comparison of students with the highest and with the lowest muscular strength showed that the former had a lower rate of symptom detection than the latter – 19.3% vs 23%. The 25% of participants with the lowest strength scores were around 18% more likely than the strongest 25% of participants to have an adverse psychological symptom. This difference was bigger for males than for females.
“Male junior high school students had a higher detection rate of psychological symptoms than female students. It was reported that male teenagers typically have more bad health habits than female teenagers, such as more time spent playing online games or watching videos, smoking, and drinking, resulting in a higher rate of psychological symptoms,” the study authors report.
The detection rate of psychological symptoms of junior high school students was higher than that of senior high school students. This can be attributed to the fact that junior high school students are in a rather unstable state of mind at the peak of their puberty, while high school students have better psychological knowledge and can better adjust to their psychological state,” the researchers add.
Adverse psychological symptoms were somewhat more common among rural students. The researchers explain that this might have to do with lower educational level of parents of adolescents from rural areas.
While a large national sample from China is a clear strength of this study, there are also limitations to be considered. Namely, the study design does not allow cause-and-effect conclusions and psychological symptoms were assessed using self-reports with all the limitations this approach entails. It should also be noted that worsening physical condition can sometimes happen as a consequence of the progression of certain adverse mental conditions.
The study, “Correlations between muscle strength and psychological health in Chinese adolescents: a cross-sectional analysis”, was authored by Jinkui Lu, Hao Sun, Ningling Liu, Jianhua Qiu and Xiaofei Xia.
