LEPTIN RESPONSE TO TWO HOURS OF
ROWING IN COLLEGE-LEVEL FEMALE ROWERS
LEPTINSKI ODZIV NA DVOURNO VESLANJE
PRI VESLAČICAH »COLLEGE« KAKOVOSTI
Jaak Jürimäe
Toivo Jürimäe
10
Jürimäe, J., & Jürimäe, T. (2002). Leptin response to two hours of rowing in college-level female rowers KinSI 8(1), 10–13
Abstract
The plasma leptin response to a single endurance row-
ing training session in 10 female college level single scull
rowers was investigated. All venous blood samples were
obtained during the follicular phase of the menstrual cy-
cle. At first, resting blood samples were obtained in the
morning after an overnight fast twice with 48 h between
sampling (leptin concentration: 11.0±8.1 vs 11.6±9.4
ng.ml
-1
; p=0.97). Venous blood samples were also ob-
tained after on-water rowing lasting about 2 h (7518 ±
293 s; distance covered 18.9 ± 1.4 km; heart rate 150 ±
7 beats.min
-1
). Blood lactate concentration did not
change significantly during training session (from 1.6 ±
0.4 to 1.9 ± 0.5 mmol.l
-1
) indicating that training was
performed at moderate intensities. Leptin values were
significantly reduced after prolonged rowing by a mean
44%. Insulin and glucose values were also decreased af-
ter prolonged rowing. Plasma leptin concentration after
an endurance rowing training session was related (r=-
0.64; p<0.05) to the distance covered. No such relation
was observed for other measured blood biochemical
parameters. Regression analyses demonstrated a posi-
tive relationship between total body fat mass and plas-
ma leptin (R2>0.70; p<0.001) regardless of sampling
time in female rowers. In conclusion, our findings indi-
cate that a prolonged low-intensity training session re-
sults in an energy deficit beyond the threshold that is
necessary to reduce plasma leptin concentration with-
out changing body fat mass in female rowers. It was sug-
gested that plasma leptin could be regarded as a key
signal for metabolic adaptation to endurance rowing
training session in female endurance athletes.
Key words: leptin, prolonged rowing, female athletes
Dr. Jaak Jürimäe, PhD
Chair of Sport Pedagogy
University of Tartu
18. Ulikooli St.
Tartu 50090
ESTONIA
Phone: 372 7 375372
Fax: 372 7 375373
Email: jaakj@ut.ee
Izvleček
Članek proučuje odziv leptina v plazmi (leptina) na
enkratno vzdržljivostno veslaško vadbo desetih veslačic
»college« kvalitete v enojcu. Vsi venski krvni vzorci so bili
pridobljeni med folikularno fazo menstrualnega ciklusa.
Na začetku so bili krvni vzorci v mirovanju pridobljeni
zjutraj, po nočnem gladovanju, dvakrat z 48-timi urami
med vzorčenjema (koncentracija leptina: 11.0±8.1 pro-
ti 11.6±9.4 ng.ml
-1
; p=0.97). Vzorci venske krvi so bili
pridobljeni tudi po približno dvournem veslanju na vo-
di (7518±293 s; opravljena razdalja 18.9±1.4 km; srčni
utrip 150±7 u.min
-1
). Koncentracija laktata v krvi se v
toku veslanja ni bistveno spremenila (od 1.6 ± 0.4 do
1.9 ± 0.5 mmol.l
-1
), kar kaže, da je bila vadba opravlje-
na pri zmerni intenzivnosti. Vrednosti leptina so bile
značilno zmanjšane po veslanju, v povprečju za 44%,
znižane so bile tudi vrednosti insulina in glukoze.
Koncentracija leptina po veslanju je bila povezana
(r=–0.64; p<0.05) s preveslano razdaljo, za ostale izmer-
jene krvne biokemične parametre povezava ni bila
dobljena.  Regresijske analize so prikazale pozitivno
povezavo med skupno količino telesne maščobe in lep-
tinom (R2>0.70; p<0.001), ne glede na trenutek
vzorčenja. Torej naše ugotovitve kažejo, da daljša vad-
ba nižje intenzivnosti povzroči energijski deficit pod
ravnijo, ki je potrebna, da se zmanjša koncentracija lep-
tina, ne da bi hkrati bila spremenjena količina maščob-
ne mase pri veslačicah. Tako predlagamo, da je leptin
lahko uporabljen kot ključni signal za metabolično pri-
lagoditev na vzdržljivostno veslaško vadbo pri vzdr-
žljivostnih športnicah.
Ključne besede: leptin, veslanje, vzdržljivost, športnice
(Received: 20. 02. 2002 – Accepted: 11. 07. 2002)

INTRODUCTION
Leptin, the product of the ob gene, is involved in
the regulation of body weight and energy expen-
diture (Flier, 1998; Frühbeck, Jebb, & Prentice,
1998; Hickey, & Calsbeck, 2001). In humans, fast-
ing leptin concentration is reduced with weight loss
(Hickey, & Calsbeck, 2001) and increased with
overfeeding (Kolaczynski, Nyce, & Considine,
1996). Furthermore, fasting leptin is positively
linked with fat mass in both lean and obese indi-
viduals (Flier, 1998; Frühbeck, Jebb, & Prentice,
1998). In trained subjects, circulating leptin is low,
and even at biological extreme low levels of body
fat, leptin concentration is related to fat content in
female (Laughlin, & Yen, 1997) and male (Sudi et
al., 2001) athletes. Exercise studies have generally
suggested that fasting leptin concentration is not
altered independently of changes in fat mass
(Hickey, & Calsbeck, 2001). These observations to-
gether suggest that leptin may be responsive to a
disruption in energy balance. 
Endurance athletes expend considerable amounts
of energy during training and it is hypothesised that
leptin may be useful for monitoring relative training
stress in these athletes. Information regarding the
response of plasma leptin to prolonged endurance
training session is limited. In this study, female row-
ers were investigated as a large amount of muscle
mass is involved in rowing (Jürimäe, Jürimäe, &
Purge, 2001; Steinacker, 1993) and the fat free
mass also influences serum leptin concentration
(Fernandez-Real, Vayreda, Casamitjana, Gonzalez-
Huix, & Ricart, 2000). Furthermore, rowers are
characterised with a relatively high amount of body
fat compared with other endurance athletes
(Nieman et al., 1999; Steinacker, 1993). Prolonged
extensive rowing on water is the major component
of training programmes of rowers (Jürimäe,
Jürimäe, & Purge, 2001; Nieman et al., 1999). 
The purposes of this study were to: 1) determine
fasting levels of leptin on resting conditions after
an overnight fast, twice with 48 h between sam-
pling in female rowers; and 2) observe leptin re-
sponse to a single extensive endurance rowing
training session in female rowers. 
METHODS
Ten female college level rowers volunteered to par-
ticipate in the study. They had trained regularly for
the last 4.3 ± 0.6 years. The study was conducted
during pre-competition in May. The rowers were
familiarised with the procedures before providing
their written consent to participate in the experi-
ment as approved by the Medical Ethics
Committee of the University of Tartu. All subjects
were normally cycling and had menstrual cycle du-
ration of 26-35 days. They were required to have at
least three months of documented menstrual cy-
cles, and were not using the oral contraceptive pill
for at least six months preceding the study. Resting
blood samples were obtained in the morning after
an overnight fast, twice with 48 h between sam-
pling. They were not allowed to exercise between
sampling. All venous blood samples were obtained
during the follicular phase of the menstrual cycle
(Thong et al., 2000).
The height (Martin metal anthropometer) and body
mass (A&D Instruments Ltd, UK) of the participants
were measured to the nearest 0.1 cm and 0.05 kg,
respectively. Body composition was measured us-
ing dual-energy X-ray absorptiometry. Scans of the
whole body were performed on each of the sub-
jects using a Lunar DPX-IQ scanner (Lunar
Corporation, Madison, USA). 
The rowers were asked not to participate in any
physical activity in the 24 h before the training ses-
sion. The training session consisted of an on-water
prolonged sculling. Subjects reported to the train-
ing site and the first blood samples were collected
from the athletes at 08.00 h. Subjects then had their
traditional light breakfast. Single sculls rowing at an
intensity equal to approximately blood lactate lev-
el of 2 mmol.l
-1
was performed for about 2 h on
water at a temperature of 20-22 °C, humidity of
40-45% and non-windy conditions (Jürimäe,
Jürimäe, & Purge, 2001). Training started at 10.00
h after warm-up that included stretching and
jogging for 15 min. The participants then rowed for
an average of 2 h 5 min (7518 ± 293 s) over a dis-
tance of 18.9 ± 1.4 km. Heart rate was 150 ± 7
beats.min
-1
(range 144
-1
70 beats.min
-1
). The par-
ticipants were re-weighed and another venous
blood sample taken after exercise. Before exercise,
the blood lactate concentration was 1.6 ± 0.4
mmol.l
-1
, which did not change significantly during
training (1.9 ± 0.5 mmol.l
-1
). The participants were
not allowed a drink during exercise or in the first 2
h of recovery (Jürimäe, Jürimäe, & Purge, 2001).
A 10 ml blood sample was obtained from an anti-
cubital vein with the participant in the upright
position. The plasma was separated and frozen at
11
Jürimäe, J., & Jürimäe, T. (2002). Leptin response to two hours of rowing in college-level female rowers KinSI 8(1), 10–13

–20 
°
C for later analysis. Leptin was determined in
duplicate by radioimmunoassays (Mediagnost,
Tübingen, Germany). This assay has a detection
limit of 0.01 ng.ml
-1
, and intra-assay and inter-as-
say coefficient of variation (CV) was <5% and
<7.5%, respectively. Insulin was determined by
means of an immunoradiometric assay (Biosource
Europe S.A., Nivelles, Belgium) with an intra- and in-
ter-assay CV of 4.5% and 12.2% at an insulin con-
centration of 6.6 µlU.ml
-1
, respectively. Samples
from one individual were run on the same assay.
Glucose (mmol.l
-1
) was measured by means of the
hexokinase/glucose 6-phosphate-dehydrogenase
method by using a commercial kit (Boehringer
Mannheim, Mannheim, Germany).
Means and standard deviations were determined.
Leptin concentrations were log transformed to nor-
malise the distribution (Thong, McLean, & Graham,
2000). T-test for dependent samples was used to
assess training induced changes in measured vari-
ables. Regression and Pearson product moment
correlation analyses were used to evaluate associ-
ations among different variables. An alpha level of
0.05 was adopted.
RESULTS
Table 1 summarizes subject characteristics for the
10 college level female rowers. Fasting leptin
(11.0±8.1 vs 11.6±9.4 ng.ml
-1
; p=0.97), insulin
(8.1±1.9 vs 8.1±2.5 µIU.ml
-1
; p=0.89) and glucose
(5.0±0.4 vs 4.9±0.4 mmol.l
-1
; p=0.80) concentra-
tions measured twice with 48 h between sampling
in the follicular phase of the menstrual cycle were
not different. Body mass was reduced after train-
ing (Table 2). Leptin, insulin and glucose values
were also decreased after prolonged rowing.
Leptin concentration after an endurance rowing
training session was related to the distance covered
(r=-0.64; p<0.05). No such relation was observed
for body mass, insulin or glucose parameters. In ad-
dition, leptin correlated with insulin measured at
every time points (r>0.64; p<0.05). Regression ana-
lyses showed that total body fat mass was related
to plasma leptin at every time point measured
(R
2
>0.70; p<0.001). 
DISCUSSION
In this study, the effects of a prolonged endurance
rowing training session, in which there was no ele-
vation in blood lactate concentration, on plasma
leptin were assessed in college-level female rowers
at the follicular phase of the menstrual cycle. To our
knowledge, no studies have yet investigated the in-
fluence of a prolonged endurance training session
on plasma leptin concentration in a relatively ho-
mogeneous group of female athletes with relative-
ly high body mass values. Furthermore, it has to be
considered that approximately 70% of the whole
muscle mass is involved in rowing and rowers are
characterised by relatively high body fat values
compared with other endurance athletes (Jürimäe,
Jürimäe, & Purge, 2001; Steinacker, 1993). In the
present study, plasma leptin concentration was sig-
nificantly reduced as a result of training session and
related to the distance covered (r=-0.64; p<0.05).
This demonstrates that leptin reflected well the
metabolic state of athletes after the exercise ses-
sion which demanded a high energy expenditure.
All rowers of this study were tested at the follicular
phase of the menstrual cycle as there is a consi-
derable evidence that leptin may be intimately in-
volved in the regulation of reproductive function in
women athletes (Laughlin, & Yen, 1997; Thong,
McLean, & Graham, 2000). A significant rise in
plasma leptin during the late follicular and luteal
phases of the menstrual cycle has been reported
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Jürimäe, J., & Jürimäe, T. (2002). Leptin response to two hours of rowing in college-level female rowers KinSI 8(1), 10–13
Table 1. Subject characteristics for female rowers
Variable Mean ± S.D.
Age (years) 19.4±1.6
Height (cm) 173.4±5.1
Body mass (kg) 67.7±10.4
% Fat mass 28.9±8.5
Fat mass (kg) 19.7±9.2
Lean mass (kg) 46.1±3.8
Table 2. Body mass, leptin, insulin and glucose be-
fore (PRE) and after (POST) an endurance rowing
training session (Mean ± S.D.).
Variable PRE POST t p-level
Body mass (kg) 67.7±10.4 67.0±10.4* 8.434 0.001
Leptin (ng.ml
-1
) 11.6±9.4 6.5±7.1* 5.612 0.001
Insulin (µIU.ml
-1
) 10.7±2.8 8.1±2.5* -2.556 0.031
Glucose (mmol.l
-1
) 4.9±0.4 4.5±0.5* 4.892 0.001
* Significantly different from PRE; P<0.05.

in healthy women (Riad-Gabriel, Jinagouda, Shar-
ma, Boyadjian, & Saad, 1998). Fasting plasma lep-
tin (11.0±8.1 vs 11.6±9.4 ng.ml
-1
; p=0.97), mea-
sured twice with 48 h between sampling in the
follicular phase of the menstrual cycle in female
rowers was not different and was at the same range
as in other endurance-trained women athletes
(Noland et al., 2001; Thong, McLean, & Graham,
2000). 
The main finding of the present study was a mean
44% decrease in plasma leptin after an average of
2 h 5 min sculling over a distance of 18.9 ± 1.4 km
in college-level female rowers. In comparison, a
34% reduction in baseline leptin concentrations
was measured in 14 men after a 2 h treadmill exer-
cise at an intensity of 75% of their individual maxi-
mal oxygen consumption (Tuominen et al., 1997).
The results of both these studies suggest that a high
energy deficit caused by a prolonged exercise con-
tributes to the decrease in leptin levels. In agre-
ement with this, Leal-Cerro et al. (1998) reported a
significant decrease in leptin concentration after a
marathon run with a net energy expenditure of over
2800 Cal. 
Leptin concentrations measured after an endu-
rance rowing training session was related to the dis-
tance covered (r=-0.64; p<0.05). This suggests that
the leptin response depends on the total amount of
energy deficit. In accordance with our results, re-
cent review article has also proposed that if plasma
leptin concentrations are to be altered, an unde-
fined threshold for total energy deficit as a result of
either exercise training or reduced caloric intake
probably exists (Hickey, & Calsbeck, 2001). The re-
sults of the present study suggest that as training in
rowing is mainly performed beyond the threshold
of energy deficit, leptin could be regarded as an
important signal for metabolic adaptation to trai-
ning and following recovery in female rowers. 
In summary, high energy deficit caused by a pro-
longed low-intensity rowing training session
reduced plasma leptin levels in female endurance
athletes with relatively high body fat values. Furt-
hermore, circulating plasma leptin levels were sig-
nificantly related to the distance covered in college-
level female rowers. This suggests that plasma lep-
tin could be regarded as an important signal for
metabolic adaptation to endurance rowing train-
ing session in female rowers.
REFERENCES
1. Fernandez-Real, J. M., Vayreda, M., Casamitjana, R., Gonzalez-
Huix, F., & Ricart, W. (2000). The fat-free mass compartment in-
fluences serum leptin in men. Eur J Endocrinol, 14, 25-29.
2. Flier, J. S. (1998). What’s in a name? In search of leptin’s physio-
logic role. J Endocrinol Metab, 83, 1407-1413.
3. Frühbeck, G., Jebb, S. A., & Prentice, A. M. (1998). Leptin: physi-
ology and pathophysiology. Clin Physiol, 18, 399-419.
4. Hickey, M. S., & Calsbeck, D. J. (2001). Plasma leptin and exer-
cise. Recent findings. Sports Med, 31, 583-589.
5. Jürimäe, J., Jürimäe, T., & Purge, P. (2001). Plasma testosterone
and cortisol responses to prolonged sculling in male competitive
rowers. J Sports Sci, 19, 893-898.
6. Kolaczynski, J. W., Nyce, M. R., & Considine, R. V. (1996). Acute
and chronic elevations of insulin on leptin production in humans:
studies in vivo and in vitro. Diabetes, 45, 699-701.
7. Laughlin, G. A., & Yen, S. S. (1997). Hypoleptinemia in women
athletes: absence of a diurnal rhythm with amenorrhea. J Clin
Endocrinol Metab, 82, 318-321.
8. Leal-Cerro, A., Garcia-Luna, P. P., Astorga, R., Parejo, J., Peino, R.,
Dieguez, C., & Casanueva, F. F. (1998). Serum leptin levels in
marathon athletes before and after the marathon run. J Clin
Endocrinol Metab, 83, 2376-2379.
9. Nieman, D. C., Nehlsen-Cannarella, S. L., Fagoaga, O. R., Henson,
D. A., Shannon, M., Davis, J. M., Austin, M. D., Hisey, C. L.,
Holbeck, J. C., Hjertman, J. M., Bolton, M. R., & Schilling, B. K.
(1999). Immune response to two hours of rowing in elite female
rowers. Int J Sports Med, 20, 476-481.
10. Noland, R. C., Baker, J. T., Boudreau, S. R., Kobe, R. W., Tanner,
C. J., Hickner, R. C., McCammon, M. R., & Houmard, J. A. (2001).
Effect of intense training on plasma leptin in male and female
swimmers. Med Sci Sports Exerc, 33, 227-231.
11. Riad-Gabriel, M. G., Jinagouda, S. D., Sharma, A., Boyadjian, R.,
& Saad, M. F. (1998). Changes in plasma leptin during the men-
strual cycle. Eur J Endocrinol, 139, 528-531.
12. Steinacker, J. M. (1993). Physiological aspects of training in row-
ing. Int J Sports Med, 14, S3-S10.
13. Sudi, K., Jürimäe, J., Payerl, D., Pihl, E., Möller, R., Tafeit, E., &
Jürimäe, T. (2001). Relationship between subcutaneous fatness
and leptin in male athletes. Med Sci Sports Exerc, 33, 1324-1329.
14. Thong, F. S. L., McLean, C., & Graham, T. E. (2000). Plasma lep-
tin in female athletes: relationship with body fat, reproductive, nu-
tritional, and endocrine factors. J Appl Physiol, 88, 2037-2044.
15. Tuominen, J. A., Ebeling, P., Laquier, F. W., Heiman, M. L.,
Stephens, T., & Koivisto, V. A. (1997). Serum leptin concentra-
tion and fuel homeostasis in healthy man. Eur J Clin Invest, 27,
206-211.
13
Jürimäe, J., & Jürimäe, T. (2002). Leptin response to two hours of rowing in college-level female rowers KinSI 8(1), 10–13