The Impact of Intense Exercise on Semen Quality

Abstract

With expanding knowledge on the health benefits of exercise, there is an increasing demand for information on the andrological consequences of participating in sports. These consequences are especially important in the context of infertility problems worldwide. The so-called “male factor” is reported in up to 50% of couples having trouble with conception. The answer to the question, “Is physical activity good for male reproductive health?” is not straightforward. A number of studies have suggested that significant changes in semen parameters may occur due to sports training of certain types, intensities, and durations. The changes to these parameters vary in scope, direction, and magnitude. Findings in recreational athletes have also differed from those in professional athletes. This review of the current literature suggests that intense physical activity may affect the semen concentration, as well as the number of motile and morphologically normal spermatozoa. Training at higher intensities and with increased loads seems to be associated with more profound changes in semen quality. In recreational athletes, exercise has either a positive or neutral effect on semen parameters. Due to many limitations (e.g., global sperm count trends, concerns about the quality control of sperm evaluations, and new standards for semen analysis), comparisons among historical data and their interpretation are difficult.

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American Journal of Men’s Health
2017, Vol. 11(3) 654 –662
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Article
Introduction
Disturbances of reproduction are frequent in humans and
the so-called “male factor” may be the cause of infertility
in 50% of cases (Brugh & Lipshultz, 2004). At the same
time, sports and leisure exercise have become extremely
popular in the modern era. People engage in various
sports for entertainment and health, and some types of
exercise (e.g., football, running, tai chi, cricket, and table
tennis) are performed by millions.
In this context, it is important to be aware of the impact
of sports on the quality of semen. Despite the proven ben-
efits of regular exercise, there is evidence that spermato-
genesis may be hindered in physically active individuals
(Gebreegziabher, Marcos, McKinon, & Rogers, 2004;
Safarinejad, Azma, & Kolahi, 2009).
Exercise and Spermatogenesis
Apart from congenital, permanent reasons, spermatogene-
sis may be affected by testicular heat stress, oxidative stress,
endocrine pathology, improper nutrition, drug side effects,
or irradiation. Testes function properly at a temperature that
is optimally 2 °C lower than that of the core body
(Durairajanayagam, Agarwal, & Ong, 2015; Mieusset &
Bujan, 1995). Inactivity, obesity, occupational exposure to
heat (as experienced by metallurgists, bakers, and drivers),
and laptop use have been associated with elevated scrotal
temperatures. Heat stress induces germ cells apoptosis,
autophagy, DNA damage, testicular germinal atrophy, sper-
matogenic arrest, decreased levels of inhibin B, and
increased production of reactive oxygen species. Epididimal
spermatozoa present alterations of motility and viability
and functions of Sertoli and Leydig cells are compromised
under such conditions (Durairajanayagam et al., 2015).
With regard to sports, elevated scrotal temperatures that
might be expected in motor sports, cycling, or horseback
riding, were indeed observed in car drivers (Bujan, Daudin,
Charlet, Thonneau, & Mieusset, 2000) and to some degree
in cyclists (Jung, Strauss, Lindner, & Schuppe, 2008). In
men participating in these activities, spermatogenesis may
669045JMHXXX10.1177/1557988316669045American Journal of Men’s HealthJóźków and Rossato
research-article2016
1University School of Physical Education, Wrocław, Poland
2University of Padua, Padua, Italy
Corresponding Author:
Paweł Jóźków, Department of Sports Medicine, University School of
Physical Education, Ul. Paderewskiego 35, Wrocław 51-612, Poland.
Email: jozkow@gmail.com
The Impact of Intense Exercise on
Semen Quality
Paweł Jóźków, MD, PhD1 and Marco Rossato, MD, PhD2
Abstract
With expanding knowledge on the health benefits of exercise, there is an increasing demand for information on the
andrological consequences of participating in sports. These consequences are especially important in the context
of infertility problems worldwide. The so-called “male factor” is reported in up to 50% of couples having trouble
with conception. The answer to the question, “Is physical activity good for male reproductive health?” is not
straightforward. A number of studies have suggested that significant changes in semen parameters may occur due to
sports training of certain types, intensities, and durations. The changes to these parameters vary in scope, direction,
and magnitude. Findings in recreational athletes have also differed from those in professional athletes. This review of
the current literature suggests that intense physical activity may affect the semen concentration, as well as the number
of motile and morphologically normal spermatozoa. Training at higher intensities and with increased loads seems to
be associated with more profound changes in semen quality. In recreational athletes, exercise has either a positive
or neutral effect on semen parameters. Due to many limitations (e.g., global sperm count trends, concerns about the
quality control of sperm evaluations, and new standards for semen analysis), comparisons among historical data and
their interpretation are difficult.
Keywords
andrology, male reproductive health, exercise

Jóźków and Rossato 655
be altered and even completely inhibited after the core body
temperature is reached. Differences in the impacts of tight-
versus loose-fitting underwear should be addressed, as
higher scrotal temperatures have been reported in men
wearing tight clothing (Jung & Schuppe, 2007).
The effects of a prolonged period of a moderately
increased scrotal temperature are similar to those of a
relatively large increase in scrotal temperature over a
shorter period of time (Hjollund, Bonde, Jensen, & Olsen,
2000). On the other hand, studies performed on men
seated for sustained periods of time (or those wearing
tight underwear) have concluded that a reduced sperm
count does not have a substantial impact on fertility (Stoy,
Hjollund, Mortensen, Burr, & Bonde, 2004). Some results
even question the hypothesis that higher scrotal tempera-
tures cause alterations in spermatogenesis (Jung &
Schuppe, 2007; Wang et al., 1997).
In animal models, mechanisms leading to heat-related
disturbances in spermatogenesis involve the increased
expression of hypoxia-inducible factor 1 alpha mRNA
(HIF1A), heme oxygenase 1, and the antioxidant enzymes
glutathione peroxidase 1 and glutathione S-transferase
alpha, translocation of the HIF1A protein into germ cell
nuclei, increased expression of the effector caspase and
cleaved caspase 3, and reduced expression of the inhibitor
of caspase-activated DNase protein. The changes are con-
sistent with a strong oxidative stress response, germ cell
death and an increased rate of DNA fragmentation (Paul,
Teng, & Saunders, 2009). In men, a commonly diagnosed
problem of varicocoele leads not only to alterations of
spermatogenesis through generation of reactive oxygen
species but also testicular heat stress and local ischaemia
(Agarwal, Hamada, & Esteves, 2012). Changes in the hor-
monal hypothalamo–pituitary–gonadal axis may affect
spermatogenesis as well. Exercise leads to fluctuations in
the secretion of gonadotropins and androgens. It is assumed
that testosterone concentration is elevated after bouts of
resistance exercise (Vingren et al., 2010). To the contrary,
prolonged endurance training (of 60 weeks duration) was
associated with a tendency toward reduced testosterone
concentrations and hypogonadotropic hypogonadism
(Safarinejad et al., 2009). The effects of systematic physi-
cal activity on the hypothalamo–pituitary–gonadal axis are
still debatable. Hypothetically, secretion of androgens in
athletes may be reduced due to suppressed release of
gonadotropins and direct/indirect effects of increased cor-
ticotropin-releasing hormone, corticotropin, cortisol, cate-
cholamines, or prolactin (Jozkow & Medras, 2012).
So-called functional hypogonadotropic hypogonadism that
occurs in patients with endocrine pathologies (leasions of
the pituitary and the hypothalamus, hyperprolactinemia,
therapy with sex steroids, glucocorticoids, or GnRH ana-
logues), brain injuries, severe chronic illnesses, eating dis-
orders and malnutrition, metabolic states (obesity,
metabolic syndrome, diabetes mellitus), is also diagnosed
in athletes after strenuous exercise (Lenzi et al., 2009).
Other factors affecting the quality of semen are discussed
further.
Active Lifestyle and Semen
It has been suggested that physical inactivity may be asso-
ciated with reduced semen quality (Stoy et al., 2004) and
indeed sedentarism/obesity turned out to be correlated
with a lower sperm count (Magnusdottir, Thorsteinsson,
Thorsteinsdottir, Heimisdottir, & Olafsdottir, 2005). In
addition, television watching appears to be inversely asso-
ciated with the sperm concentration and total sperm count
(Gaskins et al., 2015).
The association between physical activity and semen
quality is not so obvious; this lack of an apparent associa-
tion may be explained by several potential factors. The
results of andrological investigations are difficult to com-
pare due to their heterogeneity. Studies are often con-
ducted on populations that are subfertile or infertile
(Gaskins et al., 2014; Wise, Cramer, Hornstein, Ashby, &
Missmer, 2011), and doubts are regularly raised about the
quality control of semen analysis techniques. In addition,
physical activity (as a variable) cannot be easily quanti-
fied using the currently available tools.
Observational Studies
Some authors have suggested that the level of physical
activity is not related to semen quality; however, data rel-
evant to this topic are contradictory (Table 1).
Semen parameters did not correlate with regular exer-
cise in a study of 2,261 men attending fertility clinics in
the United States (Wise et al., 2011). Furthermore, no rela-
tionship was detected between exercise (i.e., frequency,
type, and duration) and sperm parameters in detailed
semen analysis (Wogatzky et al., 2012). Findings of rela-
tively large cohort studies conducted on general popula-
tions in America and student populations in Europe have
also failed to provide evidence of such an association
(Eisenberg et al., 2014; Minguez-Alarcon et al., 2014).
Interestingly, physically active subjects from Spain
have been reported to have higher numbers of motile
spermatozoa and spermatozoa with normal morphology
than sedentary controls (Vaamonde et al., 2012).
Moreover, a higher level of physical effort has been asso-
ciated with an increased sperm count and concentration
among American students (Gaskins et al., 2015). In addi-
tion, the sperm concentration was reported to be 43%
higher in men who engaged in moderate/vigorous exer-
cise among a population of 231 men seeking infertility
treatment (Gaskins et al., 2014).
Comparisons of semen samples from sport professionals,
recreational athletes, and sedentary controls from Iran have
revealed physical activity–dependent differences in semen

656 American Journal of Men’s Health 11(3)
status similar to those cited above. The sperm volume, num-
ber, as well as the percentages of motile and morphologi-
cally normal spermatozoa, were the highest among
recreational athletes (Hajizadeh Maleki et al., 2012). Further
analysis of the same population has suggested that intense
training (as with elite sportsmen) is correlated with decreases
in the volume and number of spermatozoa, the sperm con-
centration, and the percentages of motile and morphologi-
cally normal spermatozoa (Tartibian & Maleki, 2012).
Intervention Studies
Sports pose discipline-specific burdens. There are con-
siderable differences in the outcomes of the workouts of
a skier in the winter and a football player in the summer,
even if the duration and intensity are equal. Nevertheless,
investigations with controlled training/exercise stimuli
can provide some common observations.
For example, recent studies have reported evidence of
decreased sperm concentrations in cyclists and mountain
trekkers after periods of intense physical effort (Hajizadeh
Maleki et al., 2012; Hajizadeh Maleki & Tartibian, 2015;
Maleki, Tartibian, & Vaamonde, 2014). Semen volume
tends to increase after training (Denham, O’Brien, Harvey,
& Charchar, 2015; Maeshima, Tanaka, Matsuda, & Harada,
2012). Furthermore, the sperm count tends to increase after
4 weeks of training (30 minutes per session three times a
week for 1 month, at 40% or 80% of the participants maxi-
mum heart rate; Maeshima et al., 2012) but to decrease after
60 weeks of high (compared with moderate) intensity train-
ing (80% vs. 60% maximal oxygen uptake; Safarinejad
et al., 2009). The percentage of normal morphology sper-
matozoa (Hajizadeh Maleki & Tartibian, 2015; Maleki
et al., 2014) and their motility may also be reduced in ath-
letes undergoing intensive cycling training for 16 weeks
(Hajizadeh Maleki & Tartibian, 2015), running on a tread-
mill five times a week, for 120 minutes, at 60% to 80% of
maximal oxygen uptake, for 60 weeks (Safarinejad et al.,
2009), or trekking in the high mountains for 6 to 8 hours a
day for 5 days (Verratti et al., 2016; Table 2).
Earlier studies have reported that the sperm concentra-
tion is decreased by different types of training continued
for 14 to 33 days (Aitken, Buckingham, Richardson,
Gardiner, & Irvine, 2000; Vaamonde, Da Silva, Poblador,
& Lancho, 2006; Verratti et al., 2008). Sperm motility has
been demonstrated to be lower than that at baseline in
men who participate in cycling (Hajizadeh Maleki et al.,
2012), in those exposed to high altitudes (Verratti et al.,
2008), and in those who participate in diving (Aitken
et al., 2000). Exercise has also been related to a decreased
proportion of morphologically normal spermatozoa in
several studies (Hajizadeh Maleki et al., 2012; Vaamonde
et al., 2006; Verratti et al., 2008).
The major limitation of the studies presented above is
their small population sizes; authors obtained data using
only three (Aitken et al., 2000), eight (Vaamonde et al.,
2006), and six subjects (Verratti et al., 2008), respec-
tively. Another limitation was the variable time points
used for postexercise sperm evaluations. The samples in
the aforementioned studies were collected at 80 and 243
days after exercise; immediately after exercise and after 3
days; and immediately after exercise, after 1 month, and
after 3 months, respectively.
Examples of Sport Disciplines
Cycling
Cycling is one of the most troublesome activities for fer-
tility due to the mechanical impact sustained from sitting
Table 1. Recent Observational Studies of the Overall Relationship Between Physical Activity and Semen Quality.
Author Subjects
Effects of physical activity on semen
parameters
Gaskins et al. (2015) University students (n = 189) ↑ Concentration, count
Gaskins et al. (2014) Men treated for infertility (n = 231) ↑ Concentration
Eisenberg et al. (2014) General population (n = 468) No effects
Minguez-Alarcon, Chavarro,
Mendiola, Gaskins, and Torres-
Cantero (2014)
University students (n = 215) No effects
Hajizadeh Maleki, Tartibian, Eghbali,
and Asri-Rezaei (2012)
Elite athletes (n = 56), recreationally
active men (n = 52), sedentary controls
(n = 53)
Recreationally active men had ↑ volume, ,
count, motility, and normal morphology
Tartibian and Maleki (2012) Elite athletes (n = 56) versus
recreationally active men (n = 52)
↓ Volume, count, motility, and normal
morphology
Vaamonde, Da Silva-Grigoletto,
Garcia-Manso, Barrera, and
Vaamonde-Lemos (2012)
Physically active men (n = 16) versus
sedentary controls (n = 15)
↑ Motility and normal morphology
Wogatzky et al. (2012) Men treated for infertility (n = 1,683) No effects
Wise et al. (2011) Men treated for infertility (n = 2,261) No effects (apart from those in men who
cycled for >5 hours/week)

657
Table 2. Most Recent Investigations of the Effects of Physical Activity on Semen Quality.
Author Subjects Intervention Duration Evaluation Preexercise vs. postexercise semen evaluations
Verratti et al. (2016) Mountain trekkers
(n = 7)
Expedition to altitude of 900m to
5,895m
5 Days 3 Days after trekking No difference (apart from reduced forward motility)
Denham et al. (2015) Healthy men (n = 13),
controls (n = 11)
Sprint interval training 2x/week 12 Weeks After 12 weeks Healthy (Volume: 4.7 ± 1.4 vs. 5.17 ± 0.87 [mL];
Count: 271 ± 242 vs. 278 ± 282 [× 106])
Controls (Volume: 3.95 ± 1.7 vs. 3.97 ± 1.79 [mL];
Count: 315 ± 313 vs. 266 ± 278 [× 106]
Hajizadeh Maleki and
Tartibian (2015),
Maleki et al. (2014)
Cyclists (n = 24) Intensive cycling training 16 Weeks After 30 days of
recovery
Concentration: 255 ± 36 vs. 45 ± 20 [× 106/mL] (p <
.008)
Motile: 69 ± 17 vs. 65 ± 20 [%] (p < .008)
Normal morphology: 16±3 vs. 9 ± 3 [%] (p < .008)
Maeshima et al. (2012) Healthy men (n = 15) Ergometer (40% vs. 80% of
HRmax), 30 minutes 3x/week
4 Weeks 1 Day after
intervention
Volume: 2.2 ± 1.1 vs. 2.7 ± 1.1 [mL] (p < .05)
Count: 240 ± 71 vs. 310 ± 100 [× 106] (p < .05)
Pelliccione et al. (2011) Mountain trekkers
(n = 7)
Expedition to altitude of 5,900m 46 Days At sea level, 3 days
before and 1 day
after expedition
Concentration: 68 vs. 35 [× 106/mL] (p < .02)
Safarinejad et al. (2009) Recreational athletes
(n = 246)
High-intensity (80% VO2 max)
versus moderate-intensity
exercise (60% VO2 max), 5
sessions (120 minutes) per week
60 Weeks Immediately after
intervention and at
12, 24, and 36 weeks
of recovery
High- versus moderate-intensity exercise led to
decreased Count: 106 ± 21 vs. 161 ± 31 [× 106] (p
= .03)
Concentration: 35 ± 4 vs. 57 ± 4 [x 106/mL] (p = .02)
Motile: 48 ± 3 vs. 54 ± 3 [%] (p = .02)
Note. HRmax = maximum heart rate; VO2 max = maximal oxygen consumption.

658 American Journal of Men’s Health 11(3)
on the saddle, gonadal overheating, wearing tight clothes,
and hormonal dysfunction (hypogonadism). In a number
of studies (usually focused on road-bikers), cycling has
been associated with abnormal spermatozoa morphology
and reduced motility (Gebreegziabher et al., 2004;
Kipandula & Lampiao, 2015).
A prospective cohort study conducted in the United
States evaluated the association between semen quality
and physical activity in a large group of men attending an
infertility clinic (n = 2,261, aged 36 ± 3 years). Although
regular exercise was not associated with any semen param-
eters, cycling for ≥5 hours per week was associated with
reductions in the sperm concentration and motility (Wise
et al., 2011). Another study that examined semen samples
from 231 men referred for infertility treatment pointed to a
similar trend. Men who reported cycling for 1.5 hours or
more per week had sperm concentrations that were 34%
lower than those of men who did not ride bicycles (Gaskins
et al., 2014). Just recently, a small study identified that
young men who cycled as taxi operators had lower than
controls: semen volume, concentration, total motility, pro-
gressive motility, and higher percentage of abnormal mor-
phology sperm (Kipandula & Lampiao, 2015).
Running
Training in running affects semen as well. It is possibly due
to disturbances in the hormonal milieu (e.g., gonadotropins
and testosterone), the stress response (e.g., corticotropin-
releasing hormone, adrenocorticotropin, cortisol, and beta-
endorphins), oxidative stress, and scrotal heating.
Running a minimum mean distance of 108 km/week
for 12 months has been associated with reductions in sev-
eral semen parameters as well as sperm concentration and
motility and number of round cells. Semen profiles were
not affected in runners who covered only 40 to 56 km/
week for a year (M. J. De Souza, Arce, Pescatello,
Scherzer, & Luciano, 1994). Conversely, a prospective,
1-year-long study that examined a group of 24 marathon
runners identified negative associations between high-
intensity training and the sperm count and number of
spermatozoa with normal morphology, with sperm count
and percentage of morphologically normal spermatozoa
significantly lower after about 1 year (Jensen, Wiswedel,
McLoughlin, & van der Spuy, 1995).
A study conducted in Iran evaluated the effects of inten-
sive, long-term treadmill running on the hypothalamo–
pituitary–testicular axis in a group of 286 subjects (75% of
whom had fathered children). The participants were ran-
domized into groups and run at either a moderate (60% of
VO2 max) or high (80% of VO2 max) intensity for 120
minutes, five times a week, for 60 weeks. This period was
followed by a 36-week low-intensity recovery period.
Semen samples were collected at the initiation of the exer-
cise regimen and at consecutive visits every 12 weeks. The
results of this study suggested that high-intensity exercise
was correlated with decreases in sperm density, motility,
and morphology after 24 weeks of exercise. Continuing
with exercising caused the parameters to worsen, although
they were still within the fertile range. Reductions in sperm
parameters were also observed in the subjects running at a
moderate intensity; however, these changes did not reach
statistical significance. Most important, during the recov-
ery period, the semen parameters returned to their preexer-
cise levels (Safarinejad et al., 2009).
Mountaineering
Mountain trekkers should be aware of the potential effects
of high altitude on fecundity. Issues of concern for this
population include the direct influences of the low-oxygen
environment on spermiogenesis and spermiation, epididy-
mal dysfunction, alterations in the hypothalamo–pitu-
itary–gonadal axis, and/or hyperprolactinemia (Pelliccione
et al., 2011).
In addition to influencing the sperm concentration,
exposure to altitudes higher than 2,000m may result in
reductions in sperm motility and the number of spermato-
zoa with normal morphology (Pelliccione et al., 2011;
Verratti et al., 2008).
In six trekkers climbing to an altitude of 5,600 m, the
sperm concentrations dropped from 53 ± 18 to 16 ± 16 ×
106/mL, motility decreased from 57 ± 16 to 37% ± 7%,
and the percent of abnormal and immature spermatozoa
increased from 32 ± 5 to 47 ± 5% (after 1 month). Notably,
these changes were reversible (Verratti et al., 2008). In
the most recent study, short (5 days) exposure to hypoxia
combined with exercise (trekking to an altitude of 900m
to 5,895m above sea level) did not significantly alter
sperm parameters, apart from a marked reduction in
sperm forward motility (Verratti et al., 2016).
Effects of Doping on Semen Parameters
Anabolic androgenic steroids (AAS) are not only the
most commonly used drugs for doping among male ath-
letes but also probably the most dangerous to the repro-
ductive system. Hundreds of thousands of professional
and recreational athletes, accounting for 6.4% of men
globally, may be exposed to AAS during their lifetimes
(Nieschlag & Vorona, 2015).
Hypogonadotropic hypogonadism and a dampened
semen profile are well-known signs of AAS abuse being
sometimes described as anabolic-steroids induced hypogo-
nadism (ASIH). In athletes suffering from ASIH low or
normal concentrations of gonadotropins and low concen-
tration of testosterone are usually observed. Symptoms do
not necessarily appear abruptly. Furthermore, ASIH may
be associated with structural and genetic sperm damage
(G. L. de Souza & Hallak, 2011; Salenave, Trabado,
Maione, Brailly-Tabard, & Young, 2012). Although ASIH
is usually temporal, disturbances in hormone and sperm

Jóźków and Rossato 659
production may persist for months after AAS withdrawal
(van Breda, Keizer, Kuipers, & Wolffenbuttel, 2003). A
Finnish study of male power athletes (exposed to AAS for
between 6 months and 13 years) reported that at 6 months
after cessation of AAS use (but not after 1.5 months), the
sperm count increased from 33 ± 49 to 77 ± 70 × 106/mL
(Karila, Hovatta, & Seppala, 2004). Athletes who decide to
stop taking AAS experience recovery of spermatogenesis
(usually after 6-12 months); however, the reduced sperm
count is not always reversible (Boregowda, Joels, Stephens,
& Price, 2011). Authors of the most recent recommenda-
tions on the management of ASIH noted that they were
based on the review of the literature and expert opinions as
high-quality studies on patients with ASIH were lacking
(Rahnema, Lipshultz, Crosnoe, Kovac, & Kim, 2014).
Genital Trauma
Scrotal injuries may occur in men participating in certain
sport disciplines, and they represent threats to fertility.
The relationship of such injuries with semen quality has
not yet been examined.
In a recent survey, 18% of male American students
reported that they had suffered from a testicular injury
(Bieniek & Sumfest, 2014). In yet another investigation
of 755 male athletes aged 12 to 25 years, 20% of emer-
gencies due to genital trauma involved a risk of perma-
nent injury (Congeni, Miller, & Bennett, 2005).
Furthermore, in a study of extreme mountain bikers from
Austria who were especially prone to genital trauma but
who had no history of major incidents, scrotal ultrasound
examination revealed abnormalities in 94% of the men
(Frauscher et al., 2001).
It can be speculated that microtrauma sustained by tes-
ticles or the prostate gland during exercise may affect
semen variables. A few authors reported that prostate-
specific antigen (PSA) increases after cycling. At the same
time, PSA concentration turned out to be inversely related
to semen volume, sperm concentration, and progressive
motility (Ausmees et al., 2014). Nevertheless, other reports
identified that PSA concentration is not influenced by
exercise in young subjects (Banfi, Pontillo, Dolci, & Roi,
1997), and levels of PSA and free PSA in elite cyclists are
the same as in sedentary controls (Lippi et al., 2005).
Factors That Affect the Quality of
Semen
Semen quality is dependent on biological, environmental,
and lifestyle factors. There is strong evidence that the
perinatal period is related to intact spermatogenesis dur-
ing adulthood. In many cases, male infertility may be
linked to Sertoli-cell-only syndrome, immature, undiffer-
entiated Sertoli cells, microliths, or Leydig cell nodules.
Other relevant factors include disorders of sexual devel-
opment, which may be mild or severe.
Problems with spermatogenesis that arise during
development are usually permanent. In contrast, the
potentially detrimental effects of the environment, life-
style, and diet are avoidable.
Both acute and chronic medical conditions may transiently
or permanently affect gonadal function. In previous centuries,
infectious diseases posed the greatest threat to gonadal func-
tion. Currently, altered spermatogenesis is observed in men
with liver pathology, those who have received chemotherapy
and those with sleep apnea (Hammoud, Carrell, Gibson,
Peterson, & Meikle, 2012; Sharpe, 2010).
Medications that are suspected to interfere with semen
quality include antidepressants, calcium channel block-
ers, alpha-adrenergic blockers, antiepileptics, and antiret-
roviral drugs. In a study of 165 men with idiopathic
infertility, the withdrawal of drugs (antihistamines, anti-
biotics, or antiepileptics) resulted in improvements in
semen quality and the conception rate (93% and 85%,
respectively) compared with a control group that did not
stop treatment (12% and 10%, respectively; Hayashi,
Miyata, & Yamada, 2008).
It is also possible that disturbances in spermatogenesis
arise as a consequence of exposure to chemicals and envi-
ronmental contaminants. The following endocrine dis-
ruptors have attracted the most attention due to their
negative effects on spermatogenesis: bisphenol A, para-
bens, heavy metal ions, and insecticides. Despite exten-
sive research in this field, such associations remain
largely unconfirmed.
Other factors that interfere with male fertility include
smoking and alcohol consumption. Interestingly, the
effect of maternal smoking (during pregnancy) on sper-
matogenesis in male offspring is stronger than that of
active smoking by men. Heavy smokers have a 19%
lower mean sperm concentration and a 29% lower total
sperm count than nonsmokers (Ramlau-Hansen et al.,
2007). In contrast with the detrimental effects of heavy
drinking, moderate alcohol consumption has a moderate
impact on sperm and thus fertility (Alvarez, 2015).
Obesity is often associated with altered sperm param-
eters. Azoospermia and oligozoospermia occur more fre-
quently in obese and overweight subjects (Sermondade
et al., 2013). An increased body mass index is associated
with a reduced blood testosterone concentration and an
increased estradiol concentration (Rohrmann et al.,
2011). The frequency of obesity in infertile men is higher
than in those with a normal sperm count (Sharpe, 2010).
One may assume that the negative effect of obesity on
male fertility is small to moderate.
The quality of human semen may also vary seasonally,
although it is not as evident in humans as it is in animals.
Semen volume, sperm concentration, and the percentage
of spermatozoa with normal morphology are all lower
during the summer than during other periods of the year.
The sperm count may decrease by up to 30% during the
summer months (Jorgensen et al., 2001).

660 American Journal of Men’s Health 11(3)
Sperm motility at temperatures of 10 °C to 20 °C (dur-
ing the winter and spring) is higher than that during
warmer seasons, and the percentage of spermatozoa with
head defects is lower during the winter (Zhang et al.,
2013). These findings are consistent with observations
made in individuals working outdoors, which is a typical
environment for many sports. Seasonal changes in sperm
parameters are also present in subjects working in air-
conditioned spaces (Levine et al., 1992). The latter should
be considered in athletes exercising in sport halls.
The effects of socioeconomic and psychological influ-
ences on the semen profile and male fecundity are less
clear (Jozkow & Medras, 2012; Li, Lin, & Cao, 2011).
Discussion and Conclusions
The authors are aware of the potential pitfalls of the cur-
rent review. Most recent studies on this topic were per-
formed on small numbers of subjects: between 7 and 246
in intervention trials and between 16 and 2,261 in cross-
sectional designs. Furthermore, a few studies might have
been biased by inclusion of infertile/subfertile men (Wise
et al., 2011; Wogatzky et al., 2012). In addition, it cannot
be ruled out that associations between physical activity
and semen quality vary in populations of different genetic
backgrounds. Also, the methodology of the semen analy-
sis (time of semen acquisition, time of evaluation, labora-
tory technique), the range of evaluated parameters, and
the laboratory quality control might have affected the out-
comes of specific investigations. To this regard, semen
samples were assessed as soon as 1 day after intervention
(Maeshima et al., 2012; Pelliccione et al., 2011), and as
late as after 36 weeks of recovery after an intervention
(Safarinejad et al., 2009). In some studies, it was not pos-
sible to evaluate sperm motility. At the same time, it is not
straightforward to compare studies in which strenuous
physical activity lasted from 5 days (Verratti et al., 2016)
to 60 weeks (Safarinejad et al., 2009). The intensity of
applied exercise/training and the sport level of enrolled
subjects differed considerably across the studies.
Moreover, control groups were not always recruited.
Another shortcoming is the fact that popular sports disci-
plines were under- and less popular (mountaineering)
overrepresented in the current analysis.
Generally, the review of the literature supports the evi-
dence that sports practice affects semen quality. In recre-
ational athletes, exercise seems to be mainly associated
with positive or neutral effects, while professionals should
be aware of potential risks. The parameters that are most
often reduced by intense training are the sperm concentra-
tion, percentage of motile spermatozoa, and percentage of
morphologically normal spermatozoa. The impacts of these
factors on fecundity are unknown. Future studies should
clarify the direction and magnitude of the effects on semen
in men participating in the most popular sport disciplines.
At this time, it seems prudent to advise all active men
to minimize scrotal heating, to maintain a proper body
mass, to avoid smoking, alcohol consumption, doping,
and environmental toxins and to address sleep apnea (if
present). These measures will have beneficial effects on
spermatogenesis and should result in healthy offspring.
Declaration of Conflicting Interest
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research,
authorship, and/or publication of this article.
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