The goal of this randomized controlled clinical trial is to investigate the effects of moderate-intensity combined aerobic and resistance exercise on semen quality in Chinese college students. The main question is aim to explore whether moderate-intensity combined aerobic and resistance exercise can improve semen quality.

Participants in the intervention group will receive moderate-intensity combined aerobic and resistance exercise three times a week for a period of 12 weeks (The time range is from March 17, 2025 to June 8, 2025. Excluding weekends, Labor Day, and the traditional Chinese Qingming Festival and the Dragon Boat Festival during that period, a total of 32 training sessions are planned). The control group are requested to maintain their normal daily activities. Both groups receive semen routine and serum sex hormones testing before and after the intervention.

Researchers will compare the change in semen routine parameters from baseline to post-intervention at 12 weeks between the intervention and control groups.

Investigators will conduct a randomized controlled trial to examine whether moderate-intensity combined aerobic and resistance exercise can improve semen quality. A total of 60 participants will be recruited from one university. Inclusion criteria were college students aged 18 to 24 who signed informed consent form, good health with no eating disorders, mental health disorders, chronic diseases, serious systemic illnesses, genitourinary diseases or infections, and were assessed as having "low" physical activity on the self-reported International Physical Activity Questionnaire (IPAQ) over the past year, with sperm progressive motility of less than 32%, at least two evaluations at three-month intervals. Exclusion criteria include smoking, alcohol dependence, and use of drugs that affect sperm production function such as hormones and antibiotics within the past 3 months, and history of reproductive system surgery (e.g., cryptorchidism, postoperative varicocele). After stratification by BMI, participants were assigned 1:1 to the intervention and control groups.

The intervention group will receive 12 weeks of moderate-intensity combined aerobic and resistance exercise training for 60 minutes three times per week on non-consecutive days (The time range is from March 17, 2025 to June 8, 2025. Excluding weekends, Labor Day, and the traditional Chinese Qingming Festival and the Dragon Boat Festival during that period, a total of 32 training sessions are planned). Aerobic exercise is carried out in the form of running and skipping rope, and resistance exercise involves different muscle groups in the upper and lower limbs of the body. All training sessions will be conducted daily at the same time (17:00-18:00) under the guidance of a professional physical education teacher and two trained postgraduate medical students. Before the official start of the exercise intervention, participants in the intervention group will undergo a pre-intervention adaptive test to determine the maximum heart rate, and the repetitions maximum (RM) for resistance training.

Training sessions begin with a 10-minute warm-up period that includes jogging and dynamic muscle stretching. This is followed by 20 minutes of running/jumping rope on the playground. Each intervention participant will wear a heart rate armband (Polar OH1, Finland) for real-time heart rate detection to maintain achievement of a predetermined target heart rate and training intensity. Target heart rate of moderate-intensity = maximum heart rate x 64%~76%. Then, after 10 minutes of rest adjustment and preparation, a 20-minute resistance training session will be performed, including all major muscle groups. Exercises for upper body muscles such as push-ups, pull-ups, and band curl; Lower body exercises included squats, tuck jump, and burpee; and exercises for core muscle groups such as plank hold, sit-ups, and hip bridge. Resistance training will start at 50% of 1RM and increases intensity by 10% after every three sessions, with two sets of repetitions and 60-90 seconds of rest between sets. By the third week, it will reach 70% of 1RM, and repeat 3 sets at 70% of 1RM starting at week 4. After the end of week 6, re-evaluate the RM every 3 weeks and repeat 3 sets at 70% of the new 1RM (i.e., starting from Week 7 and Week 10), maintaining a 60-90 second rest between each sets. The Borg rating of perceived exercise (RPE) is combined with target heart rate for monitoring exercise intensity during exercise implementation. RPE will be applied at the end of warm-up, aerobic exercise, and resistance exercise to assess the subjective perception of participants during exercise. RPE scores of 12-13 indicate moderate intensity. After resistance training, investigators will perform a 10-minute relaxation session that includes slow walking and static muscle stretching.

The control group did not receive exercise intervention and maintained their original physical activity habits. All participants were required to maintain normal dietary habits during the study period. The primary outcome of this study is to compare the change of sperm progressive motility between intervention and control groups from pre- to post-intervention at 12 weeks.

Inclusion Criteria:

1. College student, 18 to 22 years old.
2. Good health with no eating disorders, mental health disorders, chronic diseases (such as diabetes and cardiovascular diseases), serious systemic illnesses, genitourinary diseases or infections.
3. Assessed as "low" physical activity trajectory on the self-reported International Physical Activity Questionnaire (IPAQ) over the past year.
4. In the past year, sperm progressive motility of less than 32% on at least two evaluations at three-month intervals.

Exclusion Criteria:

1. Smoking and alcohol dependence.
2. Use of drugs that affect sperm production function, such as hormones and antibiotics, in the past 3 months.
3. History of reproductive system surgery (e.g., cryptorchidism, postoperative varicocele).

IPD will be only used in a peer-reviewed journal in order to protect the privacy of the study participants.