Dear editor: Combined resistance and endurance exercise training has been considered the best way to improve physical functional status.¹1. Villareal DT, Aguirre L, Gurney AB, Waters DL, Sinacore DR, Colombo E, et al. Aerobic or resistance exercise, or both, in dieting obese older Adults. N Engl J Med. 2017;376(20):1943-1955. https://doi.org/10.1056/NEJMoa1616338
https://doi.org/10.1056/NEJMoa1616338... The effects of combined exercise training are related to body composition.²2. Ha CH, So WY. Effects of combined exercise training on body composition and metabolic syndrome factors. Iran J Public Health. 2012;41(8):20-26. However, the effects of combined exercise training on hematological factors in the young population are still unclear. We examined the effects of combined exercise training on body composition and hematological factors in college students.

College students, aged 19 to 24 years, at the Korea National University of Transportation’s fitness center (Chungju-si, Chungcheongbuk-do, Republic of Korea) participated and were randomly classified into the combined exercise (n=12: men=5, women=7; age 20.33±1.30 years; height 168.75±6.81 cm; and weight 63.73±7.57 kg) or control group (n=12: men=5, women=7; age 20.67±1.16 years; height 165.83±6.83 cm; and weight 62.11±7.76 kg). They did not exercise regularly and had no physical or psychological health problems. The study was approved by the Human Care and Use Committee of the Institute of Korea National University of Transportation.

The combined exercise group performed a combined exercise program (70 minutes, twice a week for 14 weeks), which was a modified exercise protocol.²2. Ha CH, So WY. Effects of combined exercise training on body composition and metabolic syndrome factors. Iran J Public Health. 2012;41(8):20-26. The control group maintained their typical activities of daily living and diet over 14 weeks.

Obesity-related factors were measured using Inbody-720 equipment (Biospace, Seoul, Korea). Blood samples (2-3 cc) were collected using a vacuum blood-gathering tube in the morning after a 12-hour fast. They were analyzed using an IVD-A10A automated blood analyzer (Samsung, Seoul, Korea). All data are presented as a mean±standard deviation. We used 2×2 (group×time interaction) repeated measures analysis of variance (SPSS Inc., version 18.0, Chicago, IL, USA; p<0.05).

There were interaction effects on the body mass index (p=0.001) and waist-to-hip ratio (p=0.042). However, there were no interaction effects on body composition (p>0.05) (table I) and hematological factors (p>0.05) (table II).

Adolescence and early adulthood are periods of rapid physiological growth due to hormones and sexual, behavioral, neurological, and psychological changes, culminating in sexual maturity.³3. Christie D, Viner R. Adolescent development. BMJ. 2005;330(7486):301-304. https://doi.org/10.1136/bmj.330.7486.301
https://doi.org/10.1136/bmj.330.7486.301... Effects of combined exercise training on body composition and hematological factors were not observed because the physical functional status and health condition of an individual during early adulthood are the highest during the individual’s life. Combined exercise training is insufficient to improve college students’ physical functional status and health condition. Well-designed studies are necessary to evaluate this further.

There are some limitations. First, various exercise durations, intensities, times, and frequencies were not included. A more accurately designed study is needed. Second, the participants do not represent the Korean population. Third, participants comprised a low number of students. Nevertheless, this study has a strength in that it focused on assessing the effects of combined exercise training on a young population.

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