***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To investigate the effect of marathon training on hormonal and semen profiles in male athletes . DESIGN Prospect i ve longitudinal study over 1 year . SETTING Department of Obstetrics and Gynaecology , University of Cape Town , South Africa . PARTICIPANTS Twenty-four healthy male marathon runners , 25 to 54 years of age . MAIN OUTCOME MEASURES Hormonal evaluation included determination of plasma concentrations of total T , LH , FSH , PRL , E2 , and P. Semen analyses included an evaluation of count , motility , morphology , and volume . These profiles were correlated with training intensity . RESULTS The intensity of training increased significantly in the first 5 months of the study . This was accompanied by a significant rise in serum PRL levels and a fall in P levels . No other significant hormonal changes were identified . The semen volume and sperm motility and morphology fell significantly during training , but there was no significant alteration in the sperm count . CONCLUSION This longitudinal study demonstrates that endurance training can modify significantly hormonal profiles and semen parameters in long-distance runners The aim of this study was to investigate the effects of moderate-intensity continuous training ( MICT ) , high-intensity continuous training ( HICT ) and high-intensity interval training ( HIIT ) on markers of male reproduction including seminal markers of oxidative stress and inflammation as well as semen quality and sperm DNA integrity in healthy human subjects . A total of 397 healthy male volunteers were screened and 280 were r and omly assigned to one of the MICT ( n = 70 ) , HICT ( n = 70 ) , HIIT ( n = 70 ) and non-exercise ( NON-EX , n = 70 ) groups . Subjects had inflammatory markers ( IL-1β , IL-6 , IL-8 and TNF-α ) , oxidants ( ROS , MDA and 8-isoprostane ) , antioxidants ( SOD , catalase and TAC ) , semen parameters and sperm DNA damage measured at baseline ( T1 ) , the end of week 12 ( T2 ) , the end of week 24 ( T3 ) , and 7 ( T4 ) and 30 days ( T5 ) after training . Chronic MICT , HICT and HIIT attenuated seminal markers of oxidative stress and inflammation with different kinetics for the three types of exercise ( P < 0.05 ) , and these changes were correlated with favorable improvements in semen quality parameters and sperm DNA integrity ( P < 0.05 ) . MICT was superior to HICT and HIIT in the improvements of markers of male reproductive function ( P < 0.05 ) . In conclusion , different exercise modalities favorably affect markers of male reproduction with different kinetics , suggesting intensity- , duration - and type-dependent adaptations to exercise training in healthy human subjects The purpose of this study was to investigate the influence of cycling on sperm characteristics .  Twenty subjects volunteered for the study , comprising 10 long distance competitive cyclists ( median 25.5 y ) and 10 sedentary controls ( median 24.5 y ) . A question naire was used to obtain a history of training , health , nutrition and life style . Semen analysis consisted of a detailed evaluation of sperm characteristics that included semen volume , sperm count , viability , motility and morphology . Compared to controls , the cyclists had a significantly lower proportion of spermatozoa with normal morphology ( medians : 41.5 % versus 19.5 % ; p < 0.01 ) and a significantly higher proportion of morphologically abnormal tapered forms ( medians : 4.5 % versus 22.5 % ; p < 0.01 ) . No significant difference in semen volume and sperm motility , viability and count was observed between the two groups . We concluded that endurance cycling appears to be associated with a significant alteration in sperm morphology The aim of the present study was to evaluate the influence of physical exercise on seminal parameters of male athletes with varicocele . Sixty healthy male volunteers ( athletes and non-athletes , n = 30 + 30 ) and 60 volunteers affected by varicocele ( athletes and non-athletes , n = 30 + 30 ) were r and omly selected for a clinical study . All subjects provided at least two semen sample s for routine microscopic analysis . Determinations for basal luteinizing hormone ( LH ) , follicle stimulating hormone ( FSH ) , prolactin , oestradiol , total and free testosterone under resting conditions were also performed . In both groups with varicocele the percentage of total and progressive forward sperm motility and the percentage of normal spermatozoa were significantly reduced . The percentage of both progressive forward motility and normal spermatozoa were significantly lower in athletes with varicocele compared with non-athletes with varicocele ( P < 0.05 ) . Only athletes with varicocele had mean left testis volume significantly lower than the contralateral testis ( P < 0.05 ) . No modifications of hormonal parameters at rest were observed in any groups . Physical activity might represent an aggravating factor for spermatogenesis in athletes with varicocele . In countries where sport eligibility is granted by an authoritative body , these results suggest the need to establish general medical criteria to guarantee the continuation of an athlete 's training whilst at the same time taking care of his reproductive health This r and omized controlled trial was conducted to examine the effects of 24 weeks of combined aerobic and resistance exercise training on seminal markers of inflammation and oxidative stress as well as markers of male reproductive function and reproductive performance in infertile patients . Of a total of 1296 infertile patients ( aged 25 - 40 years ) who were screened , 556 were r and omly assigned to exercise ( n = 278 ) and nonexercise ( n = 278 ) groups . Semen sample s were taken before and at 12 and 24 weeks as well as 7 and 30 days post-intervention . The training program reduced seminal proinflammatory cytokines ( interleukin (IL)-1β , IL-6 , IL-8 , and tumor necrosis factor alpha ) and markers of oxidative stress ( reactive oxygen species , malondialdehyde , and 8-isoprostane ) ( P < 0.05 ) . Additional improvements were also achieved in seminal antioxidant defense system ( superoxide dismutase , catalase , and total antioxidant capacity ) ( P < 0.05 ) . Training-induced changes in inflammation and oxidative stress status correlated with favorable improvements in semen parameters , sperm DNA integrity , and pregnancy rate ( P < 0.05 ) . In conclusion , these results support the evidence for the favorable effects of combined aerobic and resistance exercise training in male factor infertility OBJECTIVE To examine the association between regular physical activity and  semen quality . DESIGN Prospect i ve cohort study . SETTING Couples attending one of three IVF clinics in the greater Boston area during 1993 - 2003 . At study entry , male participants completed a question naire about their general health , medical history , and physical activity . Odds ratios ( ORs ) and 95 % confidence intervals ( CIs ) were derived using generalized estimating equations models , accounting for potential confounders and multiple sample s per man . PATIENT(S ) A total of 2,261 men contributing 4,565 fresh semen sample s were enrolled before undergoing their first IVF cycles . INTERVENTION(S ) None . MAIN OUTCOME MEASURE(S ) Semen volume , sperm concentration , sperm motility , sperm morphology , and total motile sperm ( TMS ) . RESULT ( S ) Overall , none of the semen parameters were material ly associated with regular exercise . Compared with no regular exercise , bicycling ≥ 5 h/wk was associated with low sperm concentration ( OR 1.92 , 95 % CI 1.03 - 3.56 ) and low TMS ( OR 2.05 , 95 % CI 1.19 - 3.56 ) . These associations did not vary appreciably by age , body mass index , or history of male factor infertility . CONCLUSION ( S ) Although the present study suggests no overall association between regular physical activity and semen quality  , bicycling ≥ 5 h/wk was associated with lower sperm concentration and TMS Effects of intensive exercise on hypothalamus-pituitary-testis ( HPT ) axis remain controversial . Our aim was to determine the effects of intensive , long-term treadmill running on reproductive hormones , HPT axis , and semen quality .  A total of 286 subjects were r and omly assigned to moderate-intensity exercise ( approximately 60 % maximal oxygen uptake ( VO(2max ) ) ; group 1 , n=143 ) and high-intensity exercise ( approximately 80 % VO(2max ) ; group 2 , n=143 ) groups . The two groups exercised for 60 weeks in five sessions per week , each session lasting 120 min . This was followed by a 36-week low-intensity exercise recovery period . All subjects underwent routine semen analysis . Blood sample s were drawn for the determination of the levels of the following hormones : LH , FSH , prolactin , testosterone ( T ) , free testosterone ( fT ) , inhibin B , and sex hormone-binding globulin ( SHBG ) . The HPT axis was assessed using GnRH and human chorionic gonadotropin tests . After 24 weeks of exercise , the subjects exercising with high intensity demonstrated significantly declined semen parameters compared with those exercising with moderate intensity ( P=0.03 ) . Serum T and fT began to decrease , and serum SHBG began to increase at the end of 12 weeks with both moderate- and high-intensity exercises . The serum LH and FSH concentrations decreased below the baseline level at 12 weeks in both groups ( P=0.07 in group 1 and 0.03 in group 2 ) . Both groups had blunted LH and FSH responses to GnRH . These parameters improved to their pre-exercise level during the recovery period . Long-term strenuous treadmill exercises ( overtraining syndrome ) have a deleterious effect on reproduction Objective To evaluate the seminal plasma 8-isoprostane , reactive oxygen species ( ROS ) , malondialdehyde ( MDA ) , superoxide dismutase ( SOD ) , catalase , total antioxidant capacity ( TAC ) , and levels of sperm DNA fragmentation in elite athletes and recreationally active men . Design Prospect i ve design was used for this study . Setting The study was performed in the Exercise Physiology Laboratory of the Urmia University . Participants Fifty-six elite athletes and 52 recreationally active men ( 18–28 years ) participated in this study . Intervention All subjects had a semen sampling at baseline . Main Outcome Measures Total antioxidant capacity and SOD activity were measured by colorimetric assay .  Levels of ROS were measured by a chemiluminescence assay . Malondialdehyde levels were measured by thiobarbituric acid reactive substance assay . Catalase activity was measured by monitoring the initial rate of disappearance of hydrogen peroxide . Concentration of free 8-isoprostane was measured by enzyme immunoassay method . Sperm DNA fragmentation was evaluated with the terminal deoxynucleotidyl transferase – mediated fluorescein dUTP nick end-labeling assay . Results Recreationally active men have significantly higher levels of body fat , seminal SOD , TAC , and catalase and lower levels of V[Combining Dot Above]O2max , seminal ROS , MDA , and 8-isoprostane and subsequently lower rate of sperm DNA fragmentation when compared with elite athletes ( P < 0.001 ) . Significantly negative correlation was observed between sperm DNA fragmentation with body fat , seminal SOD , catalase , and TAC levels ( P < 0.001 ) . Significantly positive correlation was observed between sperm DNA fragmentation with V[Combining Dot Above]O2max , seminal 8-isoprostane , ROS , and MDA levels ( P < 0.001 ) . Conclusion Spermatozoa from recreationally active men may be less susceptible to oxidative stress – induced DNA damage and hence infertility STUDY QUESTION Is  paternal physical activity associated with semen quality parameters and with outcomes of infertility treatment ? SUMMARY ANSWER Among men presenting for infertility treatment , weightlifting and outdoor activities were associated with higher sperm concentrations but not with greater reproductive success . WHAT IS ALREADY KNOWN Higher physical activity is related to better semen quality but no studies to date have investigated whether it predicts greater reproductive success . STUDY DESIGN , SIZE , DURATION The Environment and Reproductive Health ( EARTH ) Study is an on-going prospect i ve cohort study which enrolls subfertile couples presenting at Massachusetts General Hospital ( 2005 - 2013 ) . In total , 231 men provided 433 semen sample s and 163 couples underwent 421 IVF or intrauterine insemination cycles . PARTICIPANTS / MATERIAL S , SETTING , METHODS Leisure time spent in physical and sedentary activities over the past year was self-reported using a vali date d question naire . We used mixed models to analyze the association of physical and sedentary activities with semen quality and with clinical pregnancy and live birth rates . MAIN RESULTS AND THE ROLE OF CHANCE Men in this cohort engaged in a median of 3.2 h/week of moderate-to-vigorous activities . Men in the highest quartile of moderate-to-vigorous activity had 43 % ( 95 % confidence interval ( CI ) 9 , 
    Output:
    
Although most results point to a lack of major effects of physical activity on semen quality , recreational physical activity could have a positive effect on semen concentration or progressive motility .
On the contrary , elite physical activity could be detrimental for some semen parameters , such as progressive motility .
Regarding specific sports , a negative effect of cycling on semen concentration is suggested .
Conclusions In conclusion , recreational physical activity seems to be of benefit for men with infertility issues .