Strength Training in Endurance Runners

Abstract

This study examined effects of periodized maximal versus explosive strength training and reduced strength training, combined with endurance training, on neuromuscular and endurance performance in recreational endurance runners. Subjects first completed 6 weeks of preparatory strength training. Then, groups of maximal strength (MAX, n=11), explosive strength (EXP, n=10) and circuit training (C, n=7) completed an 8-week strength training intervention, followed by 14 weeks of reduced strength training. Maximal strength (1RM) and muscle activation (EMG) of leg extensors, countermovement jump (CMJ), maximal oxygen uptake (VO(2MAX)), velocity at VO(2MAX) (vVO(2MAX)) running economy (RE) and basal serum hormones were measured. 1RM and CMJ improved (p<0.05) in all groups accompanied by increased EMG in MAX and EXP (p<0.05) during strength training. Minor changes occurred in VO(2MAX), but vVO(2MAX) improved in all groups (p<0.05) and RE in EXP (p<0.05). During reduced strength training 1RM and EMG decreased in MAX (p<0.05) while vVO(2MAX) in MAX and EXP (p<0.05) and RE in MAX (p<0.01) improved. Serum testosterone and cortisol remained unaltered. Maximal or explosive strength training performed concurrently with endurance training was more effective in improving strength and neuromuscular performance and in enhancing vVO (2MAX) and RE in recreational endurance runners than concurrent circuit and endurance training.

Full text

Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Sports Med
accepted after revision
November 28, 2009
Bibliography
DOI http://dx.doi.org/
10.1055/s-0029-1243639
Published online: 2010
Int J Sports Med
© Georg Thieme Verlag KG
Stuttgart · New York
ISSN 0172-4622
Correspondence
Ritva S Taipale
University of Jyv ä skyl ä
Department of Biology of
Physical Activity
P.O. Box 35 (VIV)
40014 Jyv ä skyl ä
Finland
Tel.: + 358142602089
Fax: + 358142602071
ritva.taipale@jyu.fi
Key words
● ▶ concurrent training
● ▶ neuromuscular performance
● ▶ endurance performance
● ▶ running economy
● ▶ strength
Strength Training in Endurance Runners
ning speed. Thus, regardless of the divergent
adaptations of strength and endurance training,
recreational and elite endurance athletes may
perform both types of training concurrently to
optimize endurance performance.
Many diff erent models exist for periodization of
resistance training, particularly when it is per-
formed concurrently with endurance exercise.
Endurance runners often include either very lit-
tle or no resistance training in their exercise pro-
grams, especially when increases in running
volume occur, which makes the periodization of
concurrent strength and endurance training in
endurance runners very diff erent from that of
strength and power athletes. Periodized training
typically calls for periods of higher intensity /
volume of training alternated with periods of
lower intensity / volume of training. The periods
of lower intensity / volume of training may not
provide an adequate training stimulus for devel-
opment, or even maintenance of strength, a phe-
nomenon referred to as “ detraining ” . Detraining
from strength training is further characterized by
Introduction
&
Strength and endurance training are commonly
known to produce divergent adaptations. The
primary adaptation to endurance training is
improved oxygen transportation and utilization
by way of increased capillary and mitochondrial
density, as well as increased enzyme activity,
which improves oxidative energy metabolism
[3, 13] . The primary adaptation to strength train-
ing with high loads includes increases in maxi-
mal strength, resulting from improvements in
voluntary neuromuscular activation, which is
usually followed by muscle hypertrophy during
prolonged training periods [18] . Unlike strength
training, endurance running requires only repeti-
tive low force production, and even intensive up-
hill running does not induce maximal activation
of the leg muscles [38] . Nevertheless, even in
endurance sports, strength training for increases
in strength and power has been reported to be
benefi cial in leading to increases in rapid force
production e. g. contributing to increases in run-
Authors R. S. Taipale
1 , J. Mikkola
2 , A. Nummela
2 , V. Vesterinen
2 , B. Capostagno
3 , S. Walker
1 , D. Gitonga
1 ,
W. J. Kraemer
4 , K. H ä kkinen
1
Affi liations A ffi liation addresses are listed at the end of the article
Abstract
&
This study examined eff ects of periodized maxi-
mal versus explosive strength training and
reduced strength training, combined with endur-
ance training, on neuromuscular and endurance
performance in recreational endurance runners.
Subjects fi rst completed 6 weeks of prepara-
tory strength training. Then, groups of maximal
strength (MAX, n = 11), explosive strength (EXP,
n = 10) and circuit training (C, n = 7) completed an
8-week strength training intervention, followed
by 14 weeks of reduced strength training. Maxi-
mal strength (1RM) and muscle activation (EMG)
of leg extensors, countermovement jump (CMJ),
maximal oxygen uptake (VO
2MAX ), velocity at
VO
2MAX (vVO 2MAX ) running economy (RE) and
basal serum hormones were measured. 1RM and
CMJ improved (p < 0.05) in all groups accompa-
nied by increased EMG in MAX and EXP (p < 0.05)
during strength training. Minor changes occurred
in VO
2MAX , but vVO
2MAX improved in all groups
(p < 0.05) and RE in EXP (p < 0.05). During reduced
strength training 1RM and EMG decreased in
MAX (p < 0.05) while vVO 2MAX in MAX and EXP
(p < 0.05) and RE in MAX (p < 0.01) improved.
Serum testosterone and cortisol remained unal-
tered. Maximal or explosive strength training
performed concurrently with endurance train-
ing was more eff ective in improving strength
and neuromuscular performance and in enhanc-
ing vVO
2MAX and RE in recreational endurance
runners than concurrent circuit and endurance
training.
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Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
decreases in strength, muscle mass, and muscle activation [19]
that mirrors the time-course of the preceding training adapta-
tions [31] .
It has been suggested that endurance training may interfere
with strength development when strength and endurance train-
ing are performed concurrently [4, 14, 31] . When present, this
interference eff ect is predominantly attributed to a high volume
of training, high intensity training or prolonged training dura-
tion [4, 14, 22] , and may also be related to hormonal adaptations,
mechanical stress, and muscle damage [4, 24] . It might be
hypothesized that changes in concentrations of the hormones of
testosterone and cortisol also play a role in this interference
eff ect. Strength exercise typically stimulates an acute increase in
testosterone [25] , associated with anabolic processes in the body
such as muscle growth. In contrast, a chronic increase in circu-
lating basal levels of cortisol, indicating an increase in catabolic
activity, has been reported with prolonged endurance training
[41] .
Several studies have shown increases in endurance performance
resulting from the addition of various types of strength training
to endurance training regimens in endurance runners (orien-
teerers) [34] cross-country skiers [15, 27] , triathletes [29] and
previously untrained men [16, 22] . These studies have examined
maximal or explosive strength training combined with endur-
ance training, but no studies have been conducted to compare
these two diff erent strength training modes when they are com-
bined with endurance training. Improvements in endurance
performance in the previously mentioned studies have been
attributed to enhanced neuromuscular activation and improved
sport-specifi c economy rather than increases in maximal oxygen
uptake (VO
2max ). Moreover, individual performance diff erences
can be further explained by running speed at VO
2max (vVO 2max )
which is often used in the analysis of distance running perform-
ance, and for monitoring training [5] .
The primary purpose of the present study was to examine the
eff ects of periodized maximal versus explosive strength train-
ing, combined with endurance training, on neuromuscular
adaptations and changes in endurance performance in male rec-
reational endurance runners. In addition, this study examined
the eff ect of reduced strength training volume, accompanied by
increased endurance training volume, on strength maintenance
and endurance performance.
Methods
&
Subjects
A total of twenty-eight male recreational endurance runners
(age 21 – 45 years) were recruited from the region as part of a
marathon training school, and completed the study. Subjects
were fully informed about the study design, including informa-
tion on the possible risks and benefi ts of participation, prior to
signing an informed consent document. Ethical approval was
granted by the University Ethical Committee, and the study was
conducted according to the most recent Declaration of Helsinki
as well as the standards of the International Journal of Sports
Medicine [12] . Most of the subjects had previously completed
either a running marathon or half-marathon. Subjects were
divided into three groups matched for age, anthropometrics,
training experience, strength and VO
2max following baseline
testing at − 6 weeks. Groups included a maximal strength train-
ing group (MAX, n = 11, age: 35.5 ± 5.8 years, height: 178.6 ± 4.6 cm
(mean ± SD)), an explosive strength training group (EXP, n = 10,
36.4 ± 6.1 years, 180.5 ± 6.1 cm) and a circuit training control
group that acted as a control and used only their own body
weight as a load following the preparatory period (C, n = 7,
33.7 ± 8.2 years, 180.0 ± 4.5 cm). Subjects were not using medica-
tions nor did they have any injuries that would aff ect physical
performance. Following the period of reduced strength training
and increased endurance training, 2 subjects from the circuit
training group were unable to complete all testing due to minor
injuries; thus, statistics following this period are calculated sep-
arately.
Study design and training
Strength training throughout the 28-week study was focused on
the leg extensors, a major muscle group at work in human loco-
motion and in running, and was preceded by 20 – 30 min of low-
intensity endurance exercise (below aerobic threshold) [2] . The
preparatory strength training period consisted of approximately
9 training sessions completed over 6 weeks in which all subjects
performed strength training exercises using loads that pro-
gressed from 50 to 70 % 1RM, and that were similar to those used
in the training intervention ( ● ▶ Table 1 ). The preparatory period
was followed by an 8-week strength training intervention in
which groups began their specifi ed maximal, explosive or circuit
training programs, and in which strength training was to be
Table 1 Periodized strength training programs over 28 weeks of training.
6-week preparatory strength training period 8-week strength training intervention 14-week reduced volume strength training period
Maximal Strength Training
– 2 – 3 sets, 10 – 15 × 50 – 70 % 1RM squat / leg press,
knee extension, knee fl exion, lat pull-down / bench
press, calf exercises and countermovement jump
– 3 sets, 4 – 6 × 80 – 85 % 1RM squats (Smith)
and leg press
– 2 sets, 12 – 15 × 50 – 60 % 1RM calf exercise
– 3 sets, 6 – 8 × 75 – 80 % 1RM squats (Smith)
– 2 sets, 10 – 12 × 60 – 70 % 1RM knee extension, knee
fl exion, lat pull-down, calf exercises and bench press
Explosive Strength Training
– 2 – 3 sets, 10 – 15 × 50 – 70 % 1RM squat / leg press,
knee extension, knee fl exion, lat pull-down / bench
press, calf exercises and countermovement jump
– 3 sets, 6 × 30 – 40 % 1RM explosive squats
(Smith) and leg press
– 2 – 3 sets, 10 s scissor jump with 20 kg load
– 2 – 3 sets 5 maximal individual squat jumps
– 2 – 3 sets 5 maximal squat jumps (in series)
(20 kg load between 4 and 8)
– 3 sets, 6 × 30 – 40 % 1RM explosive squats (Smith)
– 3 sets, 10 s scissor jump with 20 kg load
– 3 × 5 maximal squat jumps (in series)
– 2 sets, 10 – 12 × 60 – 70 % 1RM lat pull-down, calf
exercises and bench press
Circuit Training Group
– 2 – 3 sets, 10 – 15 × 50 – 70 % 1RM squat / leg press,
knee extension, knee fl exion, lat pull-down / bench
press, calf exercises and countermovement jump
– 3 sets, 40 – 50 s of: Squats, push-ups, lunges,
sit-ups, calf-raises, back
– 3 sets, 50 s of: squats, push-ups / bench press, lunges,
sit-ups, calf-raises, back extensions, planks and
step-ups
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Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
completed approximately twice per week ( ● ▶ Table 2 ). No statis-
tically signifi cant diff erences in training frequency were observed
between training groups. In MAX and EXP, two to three minutes
of rest separated exercise sets throughout the study. C completed
exercises in series including 10 – 15 s of rest in between each
exercise.
Throughout the study, subjects concurrently performed endur-
ance training, typically on non-strength training days. During
the preparatory period and strength training intervention,
endurance training in all groups was primarily performed below
the aerobic threshold, which was individually determined for
each subject each time they were tested for maximal oxygen
uptake. Endurance training volume during the preparatory
period was at its lowest in the study in terms of both running
kilometres (km) ( ● ▶ Table 3 ) and endurance training time (aver-
age hours: min ± SD, 3:02 ± 0:51, 3:45 ± 2:19, 2:34 ± 0:46 for MAX,
EXP and C, respectively). Training volume, in terms of time,
increased (p < 0.01 in MAX, p = 0.056 (n. s) in EXP and p = 0.128
(n. s.) in C) from the preparatory period into the actual 8-week
strength training intervention (up to 4:49 ± 1:27, 4:43 ± 1:57,
4:03 ± 2:01 hours:min). In terms of running km, training volume
increased from the beginning of the study to the end of the
strength training intervention in all groups, although signifi -
cantly only in MAX and EXP ( ● ▶ Table 3 ). There were no group
diff erences in training volume (time or km) in these two peri-
ods. Endurance training consisted primarily of running, but also
occasionally included typical outdoor activities in Finland such
as cross-country skiing, cycling and Nordic walking. This “ other
training ” ranged an average of 6 to 15 km / week throughout the
entire experimental period.
Following the main training periods, including the preparatory
training period and strength training intervention, a 14-week
reduced strength and increased endurance training period was
completed as part of marathon preparation. Subjects completed
strength training ≤ 1 time per week for 14 weeks ( ● ▶ Table 2 ) for
strength maintenance purposes. At this time, running volume in
km increased signifi cantly in all groups ( ● ▶ Table 3 ). Endurance
training volume in time during this period was 5:20 ± 1:36,
4:52 ± 1:41, 4:50 ± 1:29 (hours:min) in MAX, EXP and C, respec-
tively. From the beginning of the study to the end of the study,
this increase in running volume was signifi cant (p < 0.05) in all
three training groups. No statistical diff erences in training vol-
ume either in terms of km or time of endurance training between
groups were observed during this 14-week period. Intensity of
endurance training was at its highest during this period includ-
ing training sessions that were performed above aerobic or
anaerobic thresholds. In addition, longer lower intensity train-
ing sessions were included as part of marathon preparation.
Subjects kept a training diary throughout the study recording
strength training sessions, weekly kilometres of running and
“ other ” endurance activity (cycling, cross-country skiing and
Nordic walking). Training plans were personalized based on
training ability and background and were furthermore adjusted
after each aerobic testing session ( − 6 weeks, weeks 0 and 8).
Measurements took place prior to the preparatory period ( − 6
weeks), before, during and after the strength training interven-
tion (weeks 0, 4 and 8) and after the reduced strength training
period ( + 14 weeks) ( ● ▶ Fig. 1 ) .
Measurements
&
Body composition
In addition to standing height, body mass and body composition
were measured using bioimpedance (In body 720 body composi-
tion analyzer, Biospace Co. Ltd, Seoul, South Korea). Measure-
ments were always taken in conjunction with blood tests
between 07.30 – 08.00. Thus, subjects always arrived for testing
in a fasted state helping to keep the possible confounding varia-
bles of diet and hydration status to a minimum. Subjects were
instructed to remove excess clothing, watches, jewellery, shoes
and socks prior to the measurement.
Table 2 Average strength and endurance training sessions per week over 28 weeks of training.
6-week preparatory
strength training period
8- week Strength Training
Intervention
14-week reduced volume
strength training period
Group − 6 Week 0 to Week 4 Week 4 to Week 8 + 14 Weeks
maximal strength 1.4 ± 0.0 1.7 ± 0.1 * * 1.6 ± 0.1 * * 0.6 ± 0.1 * * * , + + + , # # #
endurance 3.3 ± 0.2 3.1 ± 0.2 2.9 ± 0.2 3.6 ± 0.2
explosive strength 1.4 ± 0.1 1.7 ± 0.1 * * 1.7 ± 0.0 * * * 0.5 ± 0.1 * * * , + + + , # # #
endurance 3.9 ± 0.2 3.7 ± 0.3 3.1 ± 0.2 * * 3.7 ± 0.2 #
circuit strength 1.0 ± 0.7 1.3 ± 0.2 1.3 ± 0.4 0.5 ± 0.1
endurance 3.7 ± 0.4 3.1 ± 0.6 3.0 ± 0.7 3.6 ± 0.5
means ± SE, * = signifi cant diff erence from − 6 weeks, + = signifi cant diff erence from strength training intervention week 0 – week 4,
# = signifi cant diff erence from strength
training intervention week 4 – week 8 (
# = p < 0.05, * * = p < 0.01, * * * , + + + , ### = p < 0.001)
Table 3 Average endurance training volume in kilometers per week over 28 weeks of training and average endurance training volume in hours : minutes per
week.
Group 6-week preparatory
strength training period
8- week strength training
intervention
14-week reduced volume
strength training period
− 6 weeks week 0 to week 4 week 4 to week 8 + 14 weeks
maximal running km 19.0 ± 2.8 22.2 ± 2.5 30.3 ± 4.5 * 38.1 ± 3.4 * * * , + + + , #
explosive running km 23.5 ± 5.6 26.0 ± 4.6 38.3 ± 4.8 * * , + + 40.8 ± 5.6 * * , + +
circuit running km 21.5 ± 4.1 20.0 ± 5.0 29.8 ± 7.8 36.4 ± 5.3 * * , + +
means ± SE, * = signifi cant diff erence from − 6 weeks, +
= signifi cant diff erence from strength training intervention week 0 – week 4,
# = signifi cant diff erence from strength
training intervention week 4 – week 8,
§ = signifi cant diff erence from 8-week training intervention ( * ,
# = p < 0.05, * * , + + = p < 0.01, * * * , + + + = p < 0.001)
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Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
Muscle thickness
Muscle thickness of vastus lateralis (VL) and vastus intermedius
(VI) were measured using a compound ultrasound scanner
(Aloka SSD-2000, Aloka Co., Tokyo, Japan) [17] . The subject ’ s legs
were secured with a belt at the ankles and the knees were sup-
ported with a foam pad to avoid movement during the measure-
ments. Thickness was measured at a point marked with an ink
tattoo (similar to EMG placement) that was placed on the ante-
rior surface of the leg at 50 % length of the femur measured from
the lateral aspect of the distal diaphysis to the greater trochanter
[39] . All measurements were performed by the same individual.
Water soluble transmission gel was used to avoid unnecessary
tissue compression by the probe, and the probe was adjusted
manually until a clear image was achieved. Muscle thickness
was calculated from the average of three consecutive muscle
thickness measurements (VL + VI).
Performance Measures
&
Aerobic capacity
Endurance capacity was measured by maximal oxygen uptake
(VO
2max ) using a treadmill running protocol [28] . The running
velocity began at 8 km · h − 1 and was increased by 1 km · h − 1 every
third minute until volitional exhaustion. Treadmill incline
remained a constant 0.5 degrees throughout the test. Heart rate
was recorded continuously using a heart rate monitor (Suunto
t6, Vantaa, Finland). Mean heart rate values from the last minute
of each stage were used for analysis. Oxygen consumption was
measured breath-by-breath throughout the test using a portable
gas analyzer (Oxycon Mobile
® , Jaeger, Hoechberg, Germany) and
VO
2max was accepted as the highest average 60 s VO
2 value. Fin-
gertip blood samples were taken every 3rd minute to measure
blood lactate concentrations. For blood sampling, the treadmill
was stopped for approximately 15 – 20 s. Blood lactates were ana-
lysed using a Biosen S_line Lab + lactate analyzer (EKF Diagnos-
tic, Magdeburg, Germany). Running economy (RE) was evaluated
by examining VO
2 at 10 and 12 km · h − 1 , speeds comparable to
the marathon running speeds of our subjects. The velocity of
running at VO
2max (vVO 2max ) was calculated as follows
vVO
2max = speed of the last whole completed stage (km · h − 1 ) +
(running time (s) of the speed at exhaustion – 30 s) / (180 – 30 s) *
1 k m · h − 1 . Aerobic (AerT) and anaerobic (AnT) thresholds were
determined using blood lactate, ventilation, VO
2 and VCO 2 (pro-
duction of carbon dioxide) according to Aunola and Rusko [2] .
Strength and Power Measurements
&
One repetition maximum
One repetition maximum (maximal dynamic bilateral horizon-
tal leg press in a seated position) was measured using a David
210 dynamometer (David Sports Ltd., Helsinki, Finland) [21] .
Prior to attempting 1RM, subjects completed a warm-up con-
sisting of 5 × 70 % 1RM, 1 × 80 – 85 % 1RM and 1 × 90 – 95 % of esti-
mated 1RM, with one minute of rest between sets. Following
this warm-up, no more than 5 attempts to reach 1RM were
made. Leg extension action started from a knee angle of 65.4 ± 1.5
degrees. Subjects were instructed to grasp handles located by
the seat of the dynamometer and to keep constant contact with
the seat and backrest during leg extension to a full extension of
180 degrees. Verbal encouragement was given to promote maxi-
mal eff ort. The greatest weight that the subject could success-
fully lift (knees fully extended) to the accuracy of 2.5 kg was
accepted as 1RM.
Countermovement jump
A force platform (Department of Biology of Physical Activity,
Jyv ä skyl ä , Finland) was used to measure maximal dynamic
explosive force by countermovement jump height [7] . Subjects
were instructed to stand with their feet approximately hip-
width apart with their hands on their hips. Subjects were then
instructed to perform a quick and explosive countermovement
jump on verbal command so that knee angle for the jump was no
less than 90 degrees. Force data was collected and analysed by
computer software (Signal 2.14, CED, Cambridge, UK), which
used the equation h = I 2 / 2gm 2 to calculate jump height from
impulse (I = impulse, g = gravity and m = mass of subject).
Electromyographic activity
Electromyographic activity (EMG) was recorded from the vastus
lateralis (VL) and vastus medialis (VM) of the right leg during
1RM. Electrode positions were marked with small ink tattoos
[19] on the skin during the fi rst testing session to ensure that
electrode placement over the entire experimental period would
be consistent. The guidelines published by SENIAM [37] were
followed for skin preparation, electrode placement and orienta-
tion. Inter-electrode distance was 20 mm (input
impedance < 10 k Ω , common mode rejection ratio 80 dB, 1 000
gain). Raw signals were passed from a transmitter, positioned
around the subjects ’ waist, to a receiver (Telemyo 2400R,
Noraxon, Scottsdale, AZ, USA) from which the signal was relayed
to the computer via an AD converter (Micro 1401, CED, Cam-
bridge, UK). Whole range EMG was recorded from the starting
knee angle between 65.4 ± 1.5 degrees to full leg extension of
180 degrees, and subsequently analysed by computer software
(Signal 2.14, CED, UK).
Serum hormones
Venous blood samples (10 ml) were collected using sterile nee-
dles into serum tubes (Venosafe, Terumo Medical Co., Leuven,
Belgium) by a qualifi ed lab technician. Subjects were tested after
12 h of fasting between 07.30 – 08.00. Whole blood was centri-
fuged at 3 500 rpm (Megafuge 1.0R, Heraeus, Germany) for
6-week preparatory
strength training period
Basic endurance training
-6 0 8 +14
4
Increased volume basic
endurance training
Increased volume and intensity
of endurance training
8-week strength training
intervention
14-week reduced volume
strength training oeriod
Fig. 1 Study design including three training
periods and fi ve sets of measurements (denoted
by arrows).
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Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
10 min after which serum was removed and stored at − 8 0 ° C
until analysis. Samples were used for determination of serum
testosterone and serum cortisol. The ratio of testosterone and
cortisol (testosterone / cortisol) was also calculated. Analyses
were performed using chemical luminescence techniques
(Immunlite 1 000) and hormone specifi c immunoassay kits (Sie-
mens, New York, NY, USA). The sensitivity of testosterone and
cortisol assays were 0.05 nmol · l − 1 and 5.5 nmol · l − 1 , respectively.
The intra-assay coeffi cients of variation for testosterone and cor-
tisol were 3.9 % and 4.6 % , respectively. The inter-assay coeffi -
cients for testosterone and cortisol were 2.2 % and 7.6 % ,
respectively.
Statistical methods
Standard statistical methods were used for calculation of means,
standard deviation (SD) and standard error (SE). Group diff er-
ences were analysed using a one-way analysis of variance (One-
way ANOVA) and within group diff erences (group-by-training
interaction) were analysed using repeated measures ANOVA. In
the presence of a signifi cant F-value, post-hoc comparison of
means was provided by Fisher ’ s LSD test. The criterion for sig-
nifi cance was set at * = p ≤ 0.05, * * = p < 0.01 and * * * = p < 0.001.
Statistical analysis was completed with SPSSWIN 15.0 (SPSS Inc.,
Chicago, IL, USA).
Results
&
Signifi cant gains in 1RM were observed after the preparatory
period in MAX (p < 0.05), but not in EXP or C ( ● ▶ Fig. 2 ). During
the strength training intervention between weeks 0 and 4, sig-
nifi cant gains were observed in MAX and EXP (p < 0.01 and
p < 0.05, respectively) after which strength gains plateaued. Fol-
lowing reduced strength training, progressive decreases in
strength were observed, but this decrease was signifi cant only in
MAX (p < 0.01).
Increases in muscle activation of VL were signifi cant from
weeks − 6 to 8 in MAX and EXP (p < 0.05 and p < 0.01, respec-
tively) ( ● ▶ Fig. 3 ). Activation of VM also increased signifi cantly
over the preparatory period and the strength training interven-
tion in MAX and in EXP (results not shown, p < 0.05 and p < 0.01,
respectively). A signifi cant decrease in muscle activation of VL
was observed in MAX after the period of reduced strength
training and increased endurance training volume (p < 0.05)
( ● ▶ Fig. 3 ). No signifi cant changes in muscle activation were
observed in either VL or VM in C.
Jump height improved signifi cantly over the preparatory period
and the strength training intervention in MAX, EXP and C
(p < 0.001, p < 0.001 and p < 0.05, respectively) ( ● ▶ Fig. 4 ). During
the strength training intervention; however, signifi cant gains were
only observed in MAX (p < 0.05). A plateau in jump height was
observed in MAX and C after week 4 and in EXP after week 0.
Body mass at the beginning of the experimental period was
77.2 ± 5.5 kg in MAX, 78.4 ± 6.3 kg in EXP, and 83.8 ± 10.5 kg in C.
1RM LOAD
(kg)
*
**
***
*
*
++ +
+++
§§
220
210
200
190
180
170
160
170
Maximal Explosive Circuit
-6 weeks
Week 0
Week 4
Week 8
+14 Weeks
Fig. 2 Absolute 1RM load (mean ± SE) over 28 weeks of training
* = signifi cant diff erence from − 6 weeks, + = signifi cant diff erence from
week 0, § = signifi cant diff erence from week 8 ( * , + = p < 0.05, * * , + + ,
§ § = p < 0.01, * * * = p < 0.001).
EMG VL
(mV)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
-6 weeks Week 0 Week 4 Week 8 +14 Weeks
Maximal
Explosive
Circuit
*
**
§
++
Fig. 3 EMG of VL during 1RM over 28 weeks of training (mean ± SE).
* = signifi cant diff erence from − 6 weeks, + = signifi cant diff erence
from week 0, § = signifi cant diff erence from week 8 ( * ,
§
= p < 0.05,
* * , + + = p < 0.01).
CMJ Height
(cm)
36
34
32
30
28
26
24
22
20
18
Maximal Explosive Circuit
-6 weeks
Week 0
Week 4
Week 8
+14 Weeks
*
*
*
*
*
*
*
*
*
*
*
*
*
**
++
+
Fig. 4 CMJ jump height over 28 weeks of training (mean ± SE).
* = signifi cant diff erence from − 6 weeks, + = signifi cant diff erence from
week 0 ( * ,
+ = p < 0.05, * * * = p < 0.001).
65 VO2max
(ml.kg.min-1)
60
55
50
45
40
35
30
25
Maximal Explosive
*
Circuit
-6 Weeks
Week 0
Week 8
+14 Weeks
Fig. 5 Maximal oxygen uptake (mean ± SE) measured at − 6
weeks, weeks 0, 8 and + 14. * = signifi cant diff erence from − 6 weeks
( * = p < 0.05).
Downloaded by: University of Jyvaskyla. Copyrighted material.

Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
A small but signifi cant increase in body mass was observed in
MAX (1.4 % , p < 0.01) after 10 weeks of training (at week 4) which
was accompanied by a signifi cant increase in muscle thickness
of VL + VI (6.7 % , p < 0.001). Body mass then decreased signifi -
cantly during the fi nal 14 weeks of training ( − 1.6 % , p < 0.05)
though no signifi cant changes in body fat % or muscle thickness
were observed. In EXP, body mass decreased signifi cantly over
both strength training periods ( − 2.0 % , p < 0.05) which was
accompanied by a signifi cant decrease in body fat % that occurred
during the preparatory period ( − 7.0 % , p < 0.01). Following
reduced strength training, only a signifi cant decrease in muscle
thickness was observed ( − 5.3 % , p < 0.05). Body mass and muscle
thickness of C remained statistically unaltered throughout the
study while % body fat decreased signifi cantly over both strength
training periods ( − 6.5 % , p < 0.05).
Maximal oxygen uptake (VO
2max ) improved progressively in all
groups; however, signifi cant improvement was observed only
between weeks − 6 and 8 in MAX ( ● ▶ Fig. 5 ).
Maximal running speed at exhaustion (vVO
2max ) improved pro-
gressively throughout the study from week − 6 to the end of the
strength training intervention (week 8) in MAX, EXP and C
(p < 0.01, p < 0.001 and p < 0.05, respectively) ( ● ▶ Fig. 6 ). Signifi -
cant increases were also observed after reduced strength train-
ing in MAX, p < 0.001 and in EXP and p < 0.05, whereas in C,
vVO
2max was statistically unaltered.
Signifi cant improvements in running economy (RE) occurred at
10 km · h − 1 over the entire study from week − 6 to + 14 (p < 0.01)
in MAX while in EXP, these improvements occurred only from
week − 6 to 8 (p < 0.05) ( ● ▶ Fig. 7 ). Signifi cant improvements in
RE also occurred at 12 km · h − 1 in MAX over the entire study
from week − 6 to + 14 (p < 0.01), but not in EXP (results not
shown). No signifi cant improvements in RE were observed in C
at either speed.
Basal levels of testosterone and cortisol ( ● ▶ Table 4 ) did not
change throughout the study. The ratio of testosterone / cortisol
decreased signifi cantly during reduced strength training in MAX
(p < 0.05) ( ● ▶ Fig. 8 ).
Discussion
&
The primary fi ndings of the present study demonstrated that
maximal (MAX) and explosive (EXP) strength training groups
improved strength, power, and maximal muscle activation sys-
tematically during both the preparatory period and the strength
training intervention. Concomitantly, running velocity at VO
2max ,
(vVO
2max ) and running economy (RE) systematically and signifi -
cantly improved in both MAX and EXP with only minor changes
in VO
2max . The neuromuscular and strength changes associated
with improvements in vVO
2max and RE seemed to be more
important in augmenting endurance performance than increases
in VO
2max . The circuit training control group (C) made smaller,
but statistically signifi cant improvements in strength and power
over the preparatory strength training period and the strength
training intervention. The changes in VO
2max and RE in C were
not signifi cant, however, the change in vVO
2max was signifi cant.
Despite the apparent detraining of strength that occurred with
reduced strength training in MAX and EXP, the overall gains
from strength training remained somewhat above pre-training
values over the entire experimental period. This period, which
also included an increase in endurance training volume and
intensity, was associated with further improvements in vVO
2max
and RE.
Maximal Explosive Circuit
Week 0
-6 Weeks
Week 8
+14 Weeks
19
18
17
16
15
14
13
12
11
10
vVO2max
(km.h-1)*
*
**
*
*
*
*
*
**
*
§
§§§
+
++
Fig. 6 Velocity of running at VO 2max (vVO 2 ) (mean ± SE) measured
at − 6 weeks, weeks 0, 8 and + 14. * = signifi cant diff erence from − 6
w e e k s , + = s i g n i fi cant diff erence from week 0 and § = signifi cant diff erence
from week 8 ( * ,
+ ,
§
= p < 0.05, * * ,
§ §
= p < 0.01, * * * = p < 0.001).
Maximal Explosive Circuit
Week 0
-6 Weeks
Week 8
+14 Weeks
40
35
30
25
Running Economy (10 km.h-1)
(m1.kg-1.min-1)
*
**
§§§
Fig. 7 Running economy at 10 km · h − 1 over 28 weeks of training
(mean ± SE). * = signifi cant diff erence from − 6 weeks and § = signifi cant
diff erence from week 8 ( * = p < 0.05, * * = p < 0.01,
§ § §
= p < 0.001).
Table 4 Basal levels of serum testosterone and cortsiol (mean ± SE) over 28 weeks of training.
6-week preparatory
strength training period
8- week strength training
intervention
14-week reduced volume
strength training period
− 6 weeks week 0 week 4 week 8 + 14 weeks
testosterone maximal 17.0 ± 4.3 ¥ 18.7 ± 5.7 17.4 ± 5.4 17.7 ± 3.3 17.2 ± 3.5
(nmol / L) explosive 15.7 ± 2.0 15.9 ± 3.7 17.1 ± 3.2 16.8 ± 3.0 16.3 ± 4.2
circuit 14.6 ± 4.7 15.5 ± 4.8 15.6 ± 2.6 13.7 ± 3.8 14.8 ± 4.8
cortisol maximal 451.1 ± 65.0 440.4 ± 98.1 412.8 ± 79.9 401.9 ± 94.9 427.4 ± 79.1
(nmol / L) explosive 414.8 ± 93.5 414.6 ± 78.9 452.5 ± 134.5 437.6 ± 120.2 442.3 ± 85.0
circuit 462.2 ± 77.7 435.5 ± 118.5 471.7 ± 108.4 427.0 ± 124.7 458.3 ± 117.6
# = signifi cant diff erence between week 4 and week 8,
¥
= signifi cant diff erence between MAX and C, ( * = p < 0.05, * * = p < 0.01)
Downloaded by: University of Jyvaskyla. Copyrighted material.

Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
The total improvement in 1RM was 8 % in MA X over both strength
training periods and 3 % in EXP, but the diff erence between the
groups was not signifi cant. The increases in 1RM during the
strength training intervention alone (week 0 to 8) were similar
in both groups ( ~ 4 % ) despite the diff erent strength training pro-
grams. A diff erence in the magnitude of improvement over these
combined training periods was expected considering the pro-
gressively higher loads that MAX used for training (80 – 85 %
1RM) versus the lighter loads (30 – 40 % 1RM) used by EXP during
the intervention; however, movement patterns may not have
diff ered enough to distinctly show specifi city of training [6] . The
increases in strength that occurred in MAX and EXP, though sig-
nifi cant, were not as great in magnitude as in studies examining
only strength training in previously untrained individuals [1, 18] .
The smaller magnitude of increase observed in our study may be
related to diff erences in exercise protocols, in addition to con-
currently performed endurance training. The plateau in strength
gains that occurred in all groups following 10 weeks of training
suggests that the strength training stimulus was either not ade-
quate enough to induce additional changes, or it may indicate
some interference of endurance training on strength develop-
ment, an observation in line with e. g. Hickson [14] and Hunter
et al. [16] . The signifi cant 6 % increase in 1RM load that C experi-
enced following 10 weeks of training indicates that even low
load / intensity strength training (using only body weight for 4 of
those weeks) was suffi cient to stimulate maximal strength
improvements in individuals who have not previously used any
type of resistance training.
Signifi cant increases in muscle activation of VL and VM (an aver-
age of 18 % and 34 % in VL and VM, respectively) accompanied
the improvements in strength over the entire strength training
period in both MAX and EXP. Although caution should be exer-
cised with regards to the present ultrasound method for meas-
urement of muscle mass, our results indicated that in MAX,
strength development may have also been infl uenced by a sig-
nifi cant increase observed in muscle thickness of VL and VI.
More drastic increases in muscle mass were not expected
because training was not designed to be hypertrophic, and sub-
jects were participating concurrently in endurance exercise.
Signifi cant increases in CMJ jump height were observed in both
strength training groups; however, changes in jumping height
indicated that MAX made somewhat greater (n. s.) improve-
ments (13 % ) in explosive strength over 10 weeks of strength
training than EXP (11 % ). Although increases in jump height
seem to be more systematic in MAX than in EXP, the overall sim-
ilarity in the increases in jumping height are attributed, in part,
to 6 weeks of common training. Furthermore, this overall simi-
larity indicates that movement patterns in the subsequent max-
imal and explosive strength training intervention programs may
not have diff ered enough [6] , or that the nature of CMJ testing
might not show specifi city of training. It has been suggested that
specifi c explosive strength training adaptations may not occur
unless a subject already has an “ adequate ” level of strength and
power [32] . As a result, in recreationally trained endurance run-
ners with no strength training background, maximal strength
training may have had more of an eff ect on CMJ jump height
than more specifi c explosive strength training. Subjects were
also concurrently participating in endurance training activities,
which have been reported to hinder specifi c adaptations to
explosive resistance training [16, 22] .
Following the period of reduced strength training volume and
increased endurance training volume (and intensity), signifi cant
decreases were observed in maximal strength and muscle acti-
vation of the trained muscle groups (quadriceps femoris, VL) in
MAX while maximal strength in EXP and C remained statisti-
cally unaltered. Decreases in maximal strength, muscle activa-
tion [19] and CMJ jump height are typically associated with
reduced strength training volume [20] . Nevertheless, it is possi-
ble that these decreases were infl uenced by the progressive
increase in endurance running volume (running kilometers per
week) and intensity (training above aerobic and anaerobic
thresholds) [14] ( ● ▶ Table 3 ) from the beginning of the study to
the end of the study in all three groups. This signifi cant increase
in running kilometers coincided with plateaus / decreases in
maximal strength, explosive strength and muscle activation.
The increased endurance training (especially running) may have
also resulted in greater mechanical stress that has previously
been reported to interfere with muscle strength [4] . This fi nding
is in agreement with e. g. Hickson [14] and Hunter et al. [16]
who stated that early strength development may be hindered if
aerobic training volume is high. Endurance running involves
repeated low force production and impact loading which pro-
vides a diff erent type of stimulus than that of strength training.
Furthermore, leg muscles are not fully activated even during
high-intensity running (on horizontal and up-hill), which indi-
cates that there is a limitation to how many muscle fi bers can be
recruited to increase force production capabilities by running
[6] . Thus, the 14-week period of reduced strength training and
increased volume (and intensity) of endurance training appeared
not to have provided a suffi cient strength training stimulus to
maintain increases in muscle activation and strength made dur-
ing the preparatory period and strength training intervention.
The present study showed minimal increases in maximal oxy-
gen uptake in all three training groups with a signifi cant increase
occurring only in MAX, and only over the preparatory period
and strength training intervention. However, signifi cant
increases in vVO
2max were continuously systematic over the pre-
paratory period and strength training intervention in both MAX
and EXP. In C, the increase was signifi cant only between the
beginning of the preparatory period and the end of the strength
training intervention. Interestingly, the increase in vVO
2max con-
tinued only in MAX and EXP over the period of reduced volume
strength training and increased volume and intensity of endur-
ance training. In addition, improvements in running economy
(RE) were observed over the preparatory training period and the
strength training intervention in EXP (at 10 km · h − 1 ) and in MAX
over the entire 28 weeks of training (at 10 km · h − 1 and
Testosterone/Cortisol
(ratio)
0.050
0.055
0.050
0.045
0.040
0.035
0.030
0.025
0.020
-6 weeks Week 0 Week 4 Week 8 +14 Weeks
Maximal
Explosive
Circuit
§
Fig. 8 Ratio of serum testosterone to cortisol over 28 weeks of training.
§ = signifi cant diff erence from week 8 ( § = p < 0.05).
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Training & Testing
Taipale RS et al. Strength Training in Endurance Runners. Int J Spor ts Med
12 km · h − 1 ). Since increases observed in VO
2max were minimal,
improvements that occurred in strength, power, and muscular
activation likely contributed to improved vVO
2max and RE, and
prepared subjects for increased endurance training volume.
These observations are consistent with previous research by
Daniels et al. [9] who observed that improvements in running
performance are not necessarily related to increases in VO
2max
alone. Furthermore, research by Paavolainen et al. [35, 36] and
Nummela et al. [33] attributes improved endurance perform-
ance to sport-specifi c economy and improved neuromuscular
function. While endurance performance has typically been
determined by measurement of maximal oxygen uptake
(VO
2max ), fractional utilization of VO
2max and sport-specifi c
economy, [3] these more recent studies have suggested that
maximal anaerobic capacity and neuromuscular characteristics
are additional predictors of endurance performance.
It should be noted that although the values of aerobic fi tness
measured at the beginning of this study were representative of
recreational endurance athletes (non-elite), only minor changes
in VO
2max were expected since the training intensity for much of
the study was relatively low (below the aerobic threshold). Inter-
mittent high-intensity training, such as interval training, is
reported to be more eff ective than moderate intensity training
in improving VO
2max [40] . On the other hand, changes in other
endurance parameters such as vVO
2 and RE may still be posi-
tively infl uenced by low intensity training [3] . Improvements in
body composition, such as a decrease in mass or decreased % fat,
such as those observed in all training groups in the present study
may also positively infl uence endurance performance [10] .
Serum concentrations of testosterone and cortisol remained sta-
tistically unaltered over the entire 28-week study in all three
groups which indicated maintained homeostatic control. Over
10 weeks of strength training; however, the testosterone / cortisol
ratio tended to increase concomitantly with concurrent strength
and endurance training in MAX. Yet, following the reduced
strength training and increased endurance training period, the
serum ratio of testosterone / cortisol decreased signifi cantly 10 %
in MAX, which indicates an increase in catabolic activity. Though
signifi cant, the decrease in serum testosterone / cortisol ratio was
not below baseline; but it may have still contributed to strength
and power decreases [23] . Suppressed resting concentrations of
testosterone and elevated levels of cortisol have been reported to
occur in typical male endurance athletes [8, 11] . Mode (strength
versus endurance), intensity [41] and duration of training
[41, 42] have been reported to infl uence these hormonal concen-
trations.
In conclusion, the fi ndings of this study show that both maximal
and explosive strength training performed concurrently with
endurance training are more eff ective in improving strength,
power and muscular activation in recreational endurance run-
ners than concurrent circuit and endurance training. Improve-
ments in strength, power, and muscle activation during the
preparatory and strength training intervention periods appears
to have contributed to enhanced endurance performance by
improving vVO
2max and RE, and prepared subjects for increased
endurance training volume which occurred during the fi nal 14
week training period. Despite some detraining of strength that
occurred during this period of reduced strength training and
increased endurance training volume and intensity, overall
strength and power improvements from strength training were
maintained above pre-training values. Improvements in vVO
2max
continued further in both MAX and EXP, while improvements in
RE, continued further only in MAX. We conclude that maximal
or explosive strength training performed concurrently with
endurance training is more eff ective in improving strength and
neuromuscular performance and in enhancing vVO
2MAX and RE
in recreational endurance runners than concurrent circuit and
endurance training.
Affi liations
1 Department of Biology of Physical Activity, University of Jyv ä skyl ä , Finland
2 KIHU, Research Institute for Olympic Sports, Jyv ä skyl ä , Finland
3 UCT / MRC Research Unit for Exercise Science and Sports Medicine,
Department of Human Biology, University of Cape Town, South Africa
4 Department of Kinesiology, University of Connecticut, Storrs, United States
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