Male infertility is a significant global health concern, affecting approximately 7% of the male population and contributing to nearly half of all infertility cases in couples.1 Sperm morphology, an essential parameter of semen quality, is a critical determinant of male fertility. It refers to the size and shape of sperm, influencing their ability to penetrate and fertilize an oocyte.2 Various

factors, including genetics, environmental exposure, lifestyle, and physical activity, play a role in sperm morphology and overall reproductive health.3 Exercise is widely recognized for its benefits on cardiovascular health, metabolism, and psychological well-being. However, its impact on male reproductive health remains a topic of ongoing research. Among different exercise types, isotonic exercises—characterized by dynamic muscle contractions and joint movement, such as running, swimming, and cycling—are known to enhance cardiovascular fitness and metabolic function.4 Recent studies suggest that moderate-intensity isotonic exercise may improve sperm quality by reducing oxidative stress, enhancing hormonal balance, and promoting testicular function.5,6 Conversely, excessive or high-intensity exercise has been linked to detrimental effects on sperm morphology due to increased oxidative damage and hormonal disruptions.7 Despite growing evidence on the influence of physical activity on male fertility, the specific effects of isotonic exercise on sperm morphology remain underexplored. This study aims to investigate the relationship between isotonic exercise and sperm morphology, contributing to a better understanding of how lifestyle modifications can optimize male reproductive health.

This study was conducted in the Department of Physiology of Medical College & Hospital situated in an urban city of Maharashtra. Approval for the study was taken from scientific research committee and institutional ethics committee. Male subjects in the age group of 18-35 years, doing regular isotonic exercises (weight lifting exercises for upper limbs, lower limbs and torso in a well-equipped gymnasium having standard weights and machines) 60-90 minutes daily for at least 4-5 days per week for last 1 year and 5 years were taken respectively. A detailed of medical history, personal history and family history exercise history including place of exercise, daily hours of exercise, the daily schedule & type of exercise, total duration of exercise in years and other exercise related activities like participation in sports was recorded. For comparison, separate group of healthy subjects (only males) belonging to the same age group of 18 – 35 years, nearly same height and built were taken. They were from the same socio-economic status and ethnic group as that of study group but they had sedentary lifestyle which means that they did not participate or were not involved in regular isotonic exercises like running, jogging, brisk walking (morning walks), swimming, aerobics or any other sports activity.

The study objectives and procedure were explained to the participants and a written consent was taken. A detailed and relevant history was taken which included their personal history, past history, family history and medical history. General and systemic examination was carried out.

Subjects doing isotonic exercises <60 minutes or >90 Minutes; not doing regular isotonic exercises or doing it for < 4 days per week; with history of any chronic disease, sexually transmitted diseases and reproductive disorders; with history of use of medications such as anabolic steroids, commercially available proteins supplements, ayurvedic & homeopathic muscle boosters, energy drinks; having irregular eating patterns and history of depressive illness; having occupation with exposure to toxic agents like pesticides or high temperature conditions; on treatment with drugs like phenothiaquines, anti-hypertensive like beta blockers, antiepileptics, antibacterials  and H2 receptor antagonists; smokers & alcoholics; with history of surgery for hernia repair, trauma, hydrocele;  with presence of varicose, hydrocele, hernia; with signs of congenital or sex chromosomal abnormalities were excluded from the present study.

Finally, 90 healthy male subjects in the age group of 18 to 35 years were included in the study and were then subdivided into three groups.

Table 1 – Group division as per the criteria

Complete procedure was explained to the subjects & semen samples were collected by masturbation into a clean, sterile wide mouthed plastic semen container after a fixed abstinence period of 3 days. The semen sample was stored at room temperature and examined within 1 hour of collection but only after complete liquefaction. If any abnormalities were found in macroscopic examination of semen like delayed liquefaction (> 1 hour), hematospermia or semen volume less than 1.5ml, it was not considered for recording data. Instruments used for the study were haemocytometer, compound microscope, calibrated micropipettes, rubber gloves, droppers & wide mouthed bottle for specimen collection. Chemicals required for the study were semen diluting fluid, sodium hypochlorite (10%) & distilled water. 1 drop of seminal fluid was mixed with 2 drops of Eosin Y stain (0.5% in NaCl) on a glass slide. After 30 seconds, 3 drops of Nigrosin stain (10 % in distilled water) were added and mixed well. Blood smear like smear slide was made and air dried. 200 sperms were observed under oil immersion layer and percentage of sperms showing normal morphology was counted. According to WHO (2010) more than 4 % sperms should show normal morphology.

Table 2 – Comparison between groups with respect to age, weight, height And body mass index.  

Table 3 – Comparison between Control group A, Study group B & Study group C with respect to normal sperm morphology.

Table 4 - Bonferroni’s multiple comparison test for normal sperm morphology between controls groups     a, study group B and study group C.

Graph 1 – Graph showing comparison between control group A, study group B & study group C with                                        respect to normal sperm morphology

Table 2 indicates that there was no significant difference (p>0.05) between control group A, study group B, and study group C concerning age, weight, height, and body mass index. Therefore, these groups were comparable in terms of these parameters.

Table 3 demonstrates a highly significant difference (p<0.001) in the mean values of normal sperm morphology among the three groups. Furthermore, Table 4 and Graph 1 reveal that the mean value of normal sperm morphology was significantly higher in Group B compared to Group A and Group C. However, there was no significant difference in the mean values between Group A and Group C.

Vaamonde et al. investigated the influence of physical activity and exercise on male reproductive potential, concluding that moderate-intensity isotonic exercise positively impacted all semen parameters, including sperm morphology. Similarly, Pawet Jozkow et al. examined the effects of intense exercise on semen quality and found that short-duration moderate-intensity weight training exercises had a beneficial effect on sperm morphology.

Another study by Vaamonde et al. reported that physically active men exhibited better sperm morphology and hormone profiles than sedentary individuals. Gaskins et al. further highlighted that moderate exercise enhances semen quality, whereas prolonged sedentary behavior negatively affects sperm morphology. Safarinejad et al. demonstrated that excessive endurance exercise could result in hormonal imbalances and deteriorated sperm morphology.

Vaamonde et al. suggested that aerobic exercise reduces oxidative stress, thereby improving sperm function and morphology. Dubey et al. found that isotonic exercise enhances testicular function, leading to improvements in sperm morphology and motility. Regular isotonic exercise has been linked to better cardiovascular health, increased testosterone levels, and reduced oxidative stress, all of which contribute to improved sperm function. Additionally, exercise enhances insulin sensitivity and reduces inflammation, further improving sperm parameters, including morphology. However, excessive exercise may have a detrimental effect on normal sperm morphology due to increased oxidative stress and hormonal imbalances.

It can therefore be concluded that the levels of isotonic exercise reported in this study, performed over a duration of up to one year, exert a positive effect on sperm morphology. These findings are encouraging as they help clarify the appropriate intensity and frequency of physical activity that may enhance sperm quality or at least prevent its decline due to prolonged moderate-intensity isotonic exercises.

Such studies are rare in India and hold significant relevance in the context of primary male infertility. Therefore, further research is needed to define the optimal intensity and threshold of exercise that can be considered beneficial for improving semen parameters

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