Optimizing strength training for running and cycling endurance
performance – a review
Running head: “Strength training and endurance performance”
Bent R. Rønnestad1, Iñigo Mujika2,3
1 Lillehammer University College, Section for Sport Science, Lillehammer, Norway
2 Department of Physiology, Faculty of Medicine and Odontology, University of the Basque Country,
Leioa, Basque Country
3 School of Kinesiology and Health Research Center, Faculty of Medicine, Finis Terrae University,
Scand J Med Sci Sports. 2013 Aug 5. doi: 10.1111/sms.12104.
Bent R. Rønnestad
Lillehammer University College
PB. 952, 2604 Lillehammer
E-mail: firstname.lastname@example.org Phone: +47 61288193 Fax: +47 61288200
Here we report on the effect of combining endurance training with heavy or explosive
strength training on endurance performance in endurance-trained runners and cyclists.
Running economy is improved by performing combined endurance training with either heavy
or explosive strength training. However, heavy strength training is recommended for
improving cycling economy. Equivocal findings exist regarding the effects on power output
or velocity at the lactate threshold.Concurrent endurance and heavy strength training can
increase running speed and power output at VO2max (Vmax and Wmax, respectively) or time to
exhaustion at Vmax and Wmax. Combining endurance training with either explosive or heavy
strength training can improve running performance, while there is most compelling evidence
of an additive effect on cycling performance when heavy strength training is used. It is
suggested that the improved endurance performance may relate to delayed activation of less
efficient type II fibres, improved neuromuscular efficiency, conversion of fast-twitch type IIX
fibres into more fatigue resistant type IIA fibres, or improved musculotendinous stiffness.
Key words: Aerobic capacity, concurrent training adaptions, exercise economy, neuromuscular
function, cycling, running
The effects of strength training on endurance athletic performance have long been the subject
of debate among athletes, coaches and sport scientists. Strength training includes both
explosive strength training and heavy strength training that promote different training
adaptations. Heavy strength training can be defined as “all training aiming to increase or
maintain a muscle or a muscle group’s ability to generate maximum force” (Knuttgen &
Kraemer, 1987) and is here equal to training with a load that allows between 1 repetition
maximum (RM) and 15 RM. Explosive strength training is here defined as exercises with
external loading of 0–60% of 1RM and maximal mobilization in the concentric phase (0% of
1RM equals body weight). Performance in most endurance events is mainly determined by
the maximal sustained power production for a given competition distance, and the energy cost
of maintaining a given competition speed. In shorter endurance events and during
accelerations and sprint situations, anaerobic capacity and maximal speed may also contribute
to performance. Strength training contributes to enhance endurance performance by
improving the economy of movement, delaying fatigue, improving anaerobic capacity and
enhancing maximal speed.
Some of the early studies that investigated the effect of combining endurance and strength
training in endurance-trained athletes did not identify any additive effect on endurance
performance (Jensen, 1963; Paavolainen et al., 1991; Tanaka et al., 1993). However, recent
evidence contradicts the findings of those early studies and points towards an additive effect
of combining the endurance and strength training on running and cycling performance
(Tanaka & Swensen, 1998). At the time of this review there was a lack of good studies on
already well-trained endurance athletes, especially in cycling. The purpose of this review is to
provide an updated synopsis on the effect of combining endurance training with heavy or
explosive strength training on endurance performance in endurance-trained runners and
The effects of strength training on factors determining endurance performance
Maximal oxygen consumption
Maximal oxygen consumption (VO2max) has long been associated with success in
endurance sports (Saltin & Åstrand, 1967; Costill et al., 1973; Bassett & Howley, 2000)
and is one of the major characteristics that determine endurance performance (di
Prampero, 2003; Levine, 2008). Importantly, the highest VO2max value does not
necessarily equate to the best endurance performance, but the best endurance
performance typically demands high VO2max values (Saltin & Åstrand, 1967; Costill et
al., 1973; Lucia et al., 1998; Bassett & Howley, 2000; Impellizzeri et al., 2005). In
addition, VO2max sets the upper limit of intensity for prolonged steady-state exercise.
There is little evidence that strength training should be the primary training mode to
improve VO2max, and only a trivial effect of concurrent strength and endurance training
on VO2max compared to endurance training alone in trained cyclists (Hickson et al.,
1988; Bishop et al., 1999; Bastiaans et al., 2001; Levin et al., 2009; Rønnestad et al.,
2010a, 2010b; Sunde et al., 2010; Aagaard et al., 2011), long distance runners
(Paavolainen et al., 1999; Johnston et al., 1997; Spurrs et al., 2003; Turner et al., 2003;
Saunders et al., 2006; Mikkola et al., 2007a, 2011; Storen et al., 2008; Taipale et al.,
2010), cross country skiers (Hoff et al., 1999, 2002; Osteras et al., 2002; Mikkola et al.,
2007b; Losnegard et al., 2011; Rønnestad et al., 2012), or triathletes (Millet et al., 2002).
However, the majority of the training interventions investigating the effects of
concurrent training lasted only 8 to 12 weeks. Caution should be used when long-term
effects of concurrent training are considered.
Exercise economy has been defined as the oxygen consumption required at a given absolute
submaximal exercise intensity (Jones & Carter, 2000; Saunders et al., 2004). There is
substantial interindividual variability in exercise economy in both running and cycling despite
a similar VO2max (Conley & Krahenbuhl, 1980; Horowitz et al., 1994). The importance of
exercise economy is underlined by the close relationship with endurance performance in
trained individuals with homogenous VO2max (Costill, 1967; Conley & Krahenbuhl, 1980;
Horowitz et al., 1994). Accordingly, it is likely that any improvement in exercise economy
will be associated with improved long-term endurance performance.
Numerous studies have reported improved running economy after 8-14 weeks of concurrent
heavy strength and endurance training, while no substantial changes were observed in the
control groups (Johnston et al., 1997; Hoff & Helgerud, 2002; Millet et al., 2002; Storen et al.,
2008; Guglielmo et al., 2009; Taipale et al., 2010). Improved running economy is also evident
after 6-12 weeks of combined explosive strength and endurance training in runners
(Paavolainen et al., 1999; Spurrs et al., 2003; Turner et al., 2003; Saunders et al., 2006;
Taipale et al., 2010). Mikkola et al. (2007a) replaced some of the endurance training of young
distance runners with only one session a week of explosive strength training and did not find
changes in running economy. Given that running economy can be improved by 2-3 strength
training sessions per week, it seems a threshold of (explosive) strength training volume and
frequency has to be overcome to achieve improved running economy. When cycling economy
is measured by the same traditional method used in running (i.e. short, 3-5 min, submaximal
bouts of exercise), it appears there is little change after combining heavy strength or explosive
strength training with endurance training (Bastiaans et al., 2001; Rønnestad et al., 2010a,
2010b; Aagaard et al., 2011). However, adding heavy strength training to endurance training
can improve cycling economy after only 8 weeks (Sunde et al. 2010). The reasons for this
discrepancy remain unclear, but the lower performance level of the cyclists in the latter study
may have affected the outcome of strength training. On the other hand, by using a non-
traditional protocol to measure cycling economy during 5-min periods every half hour
throughout 3 hours of submaximal cycling, a superior improvement was observed during the
last hour after a period of concurrent heavy strength and endurance training (Rønnestad et al.
2011). Lowered heart rate at the end of 2 hours of submaximal cycling has also been observed
after 5 weeks of heavy strength training in triathletes (Hausswirth et al., 2010). Thus,
divergent findings are evident on whether performing heavy strength training together with
ordinary endurance training improves cycling economy. This shortcoming may relate in part
to methodological differences between studies. Nevertheless, there are no reports of a
negative effect of heavy strength- and explosive strength training on either cycling or running
The fraction of VO2max which can be sustained during a performance bout (performance VO2)
is associated with the degree of blood lactate accumulation during exercise (Farrell et al.,
1979; LaFontaine et al., 1981; Tanaka & Seals, 2008). Several methods have been devised to
express the relationship between blood lactate concentration ([la-]) and fraction of VO2max
(Bentley et al., 2007; Faude et al., 2009). A common term is lactate threshold, which
describes an estimation of a breakpoint on the [la-] curve as a function of exercise intensity
(Tokmakidis et al., 1998). Lactate threshold expressed as a percentage of VO2max is largely
unaffected by exercise economy and VO2max, which might explain the small correlation
between lactate threshold expressed as % VO2max and time trial cycling performance in
cyclists (Støren et al. 2012). There are numerous ways to determine the power output or speed
at the lactate threshold, resulting in diverse “thresholds” on the [la-] vs. power/speed curve
which all seem to correlate well with long-term endurance performance (Tokmakidis et al.,
1998). Any rightward movement of the [la-] curve results in improved power output/velocity
at the lactate threshold regardless of how the lactate threshold has been determined
(Tokmakidis et al., 1998). A higher velocity/power output at the lactate threshold theoretically
means that an athlete can maintain a higher velocity/power output during extended exercise.
Numerous studies report a high relationship between long-term performance and
velocity/power output at the lactate threshold in both cycling and running, and the latter is
useful for predicting endurance performance in both runners and cyclists (e.g. Farrell et al.,
1979; Coyle et al., 1988, 1991; Grant et al., 1997; Bishop et al., 1998; Lucia et al., 1998;
Impellizzeri et al., 2005; Slattery et al., 2006).
Since the majority of studies reported improved running economy in response to a period of
concurrent strength and endurance training in endurance-trained individuals, it would be
reasonable to expect an improvement in the exercise velocity or intensity associated with the
lactate threshold. This expectation is based on the assumption that the main determinants of
the lactate threshold velocity are VO2max and exercise economy (di Prampero et al., 1986), and
that VO2max is not compromised while concurrently performing strength and endurance
training. However, the endurance training literature comprises equivocal findings: some
studies report little change in the lactate threshold of runners (Paavolainen et al., 1999; Hoff
& Helgerud, 2002; Støren et al., 2008; Mikkola et al., 2011), while others observed
substantial improvements in velocity at the lactate threshold (Mikkola et al., 2007a, 2011;
Guglielmo et al., 2009; Taipale et al., 2013). Some studies report improved power output at a
certain [la-] (Koninckx et al., 2010; Rønnestad et al., 2010a, 2010b), while others report no
additional effect of performing strength training (Bishop et al., 1999; Sunde et al., 2010;
Aagaard et al., 2011). Importantly, none of the studies on long-distance runners and cyclists
report a negative effect of strength training on velocity or power output at the lactate
Other factors important for endurance performance
The key performance and physiological measures of VO2max, lactate threshold and
exercise economy explain >70% of the between-subject variance in long-duration
endurance performances (di Prampero et al. 1986).Other factors contribute to endurance
performance including running speed and power output at VO2max (Vmax and Wmax,
respectively) predict endurance performance in endurance-trained runners and cyclists,
respectively (Morgan et al., 1989; Noakes et al., 1990; Hawley & Noakes, 1992;
Yoshida et al., 1993; Billat & Koralsztein, 1996; Bentley et al., 1998; Lucia et al., 1998;
Balmer et al., 2000; Stratton et al., 2009). Both Wmax and Vmax distinguish the endurance
performance in well-trained cyclists and long distance runners, making them a useful
marker of endurance performance (Noakes et al., 1990; Lucia et al., 1998). Wmax and
Vmax are influenced by VO2max and exercise economy, but also incorporate anaerobic
capacity and neuromuscular characteristics (Jones & Carter, 2000). Anaerobic power
and neuromuscular characteristics are also involved in long-duration endurance
performance, especially when athletes are matched for aerobic capacity(Bulbulian et al.
1986; Houmar et al., 1991; Paavolainen et al., 1999b; Baumann et al., 2012).
Concurrent endurance and heavy strength training can increase Wmax/Vmax or time to
exhaustion at Wmax/Vmax (Hickson et al., 1988; Millet et al., 2002; Støren et al., 2008;
Sunde et al., 2010; Rønnestad et al., 2010a, 2010b; Taipale et al., 2010, 2013; Mikkola et
al., 2011). However, this positive effect in cyclists was not observed by using explosive
strength training (Bastiaans et al., 2001) nor after short-term (6 weeks) strength training
(Levin et al. 2009).
Another related factor important for endurance performance is the ability to generate
high power output over a short period of time to get a good position at the start of a race,
close a gap, make a critical pass, break away from the pack, or win a final sprint. Peak
power output is markedly affected by muscle cross-sectional area (Izquierdo et al. 2004)
- increased cross-sectional area of the quadriceps muscle was associated with increased
peak power output after combined heavy strength training and endurance training in
well-trained cyclists (Rønnestad et al. 2010a). Similarly, anaerobic running power can
increase substantially after a period of added explosive strength training (Paavolainen et
al., 1999; Mikkola et al., 2007a).
The traditional way of measuring cycling performance is time trialling lasting between 30 and
60 minutes. However the effects of strength training are contradictory with studies variously
showing either improvements (Hickson et al., 1988; Koninckx et al., 2010; Rønnestad et al.,
2010b; Aagaard et al., 2011) or a trivial effect (Bishop et al., 1999; Bastiaans et al., 2001;
Levin et al., 2009). When positive effects are reported, heavy strength training is performed
with multiple leg exercises. In contrast studies failing to show much improvement were
typically short-term in duration, with a low volume of strength training or using explosive
strength training. In contrast, adding both explosive and heavy strength training to endurance
training can improve running performance, while no change was observed in the control
groups performing endurance training only (Paavolainen et al., 1999; Spurrs et al., 2003;
Støren et al., 2008).
Combining heavy strength training and regular endurance training increased mean power
output production during a final 5-min all-out sprint after 3 hours of submaximal cycling by 7
%, while no changes occurred in the endurance training group (Rønnestad et al., 2011).
Not all studies, however, have reported that concurrent training results in superior endurance
performance, especially in males (Kraemer et al., 2004, Barnes et al. 2013). Nevertheless,
there are no reports of negative impacts of concurrent training on endurance performance.
A likely mechanism for improved performance after combined strength and endurance
training is (altered) muscle fibre type recruitment pattern. When measuring cycling
economy the traditional way, by measuring oxygen consumption during a short period of
time at steady state exercise intensities below the lactate threshold, mainly type I fibres
that are activated. In this setting may the effect of increasing the maximum strength of
type I fibres and postponing the activation of the less economical type II fibres be trivial
or small. This effect might explain why the literature seems is equivocal on
improvements in cycling economy in well-trained cyclists measured the traditional way.
Altered muscle fibre recruitment may also explain why improvement of cycling
economy in well-trained cyclists after a period of concurrent training is detected first
after about two hours of submaximal cycling (Rønnestad et al., 2011) It is likely that
after prolonged cycling will some of the type I fibres be exhausted and the less
economical type II fibres gradually increases their contribution to the exercise. It might
be suggested that the strength training increases the maximum strength of type I fibres
and postpones their time to exhaustion and thereby delaying the activation of type II
fibres. Strength training increases maximal force, and therefore peak force or muscle-
fibre tension developed in each movement cycle at the same absolute exercise intensity
decreases to a lower percentage of the maximal values. A cross-sectional study of
cyclists with similar VO2max and Wmax, reported lower EMG activity in the cyclists with
higher compared with lower maximal strength (Bieuzen et al. 2007).
Another potentially contributing factor to improved endurance performance is an
increased proportion of type IIA fibres and reduced proportion of type IIX fibres. A 16
week study in top-level cyclists combining heavy strength training and endurance
training in top-level cyclists examined the proportional redistribution in type II muscle
fibres (Aagaard et al., 2011). The increase in the more fatigue resistant, yet high
capability of power output, type IIA fibres may contribute to improved endurance
performance. However, there have also been reported no changes in fibre composition in
endurance athletes after a period of concurrent strength and endurance training (Bishop
et al., 1999). The different findings might be related to differences in initial percentages
of type IIX fibres (Bishop et al., 1999).
According to the size principle of motor unit recruitment (Henneman et al., 1965), the
following mechanism may be hypothesized: a reduced reliance on the less efficient type
II muscle fibres and thus improved exercise economy; slower emptying of glycogen
stores; reduced overall muscle fatigue; and a potentially increased capacity for high-
intensity performance following prolonged exercise or an increased ability by the athlete
to exercise longer until exhaustion (Hickson et al., 1988; Coyle et al., 1992; Horowitz et
al., 1994). A 12 week program of heavy strength training resulted in higher
phosphocreatine and glycogen content and lower [la-] at the end of 30 min cycling at
72% of VO2max, despite no change in VO2max (Goreham et al. 1999). The performed
strength training program was almost identical to the strength training performed in the
studies reporting a superior effect of concurrent training in long-term endurance
performance, despite the observation of no change in the traditional way of measuring
cycling economy (Aagaard et al., 2011; Rønnestad et al., 2011). The studies in which no
additive performance effect of concurrent training in cyclists was found performed either
explosive strength training with low external load (Bastiaans et al., 2001), low volume of
heavy strength training (Bishop et al. 1999), or lasted for a short duration (Levin et al.,
2009). Thus, it seems that differences in a strength training program can explain the
different findings. Explosive strength training and low-volume heavy strength training
can induce inferior strength- and hypertrophic responses compared to higher volume of
heavy strength (Rønnestad et al. 2007; Holm et al., 2008). Unfortunately, no
performance measurements were obtained in the study of Goreham et al. (1999), but the
improved aerobic metabolism and conservation of limited glycogen stores are important
for long-term endurance performance. Interestingly, they did not observe any change in
Another putative mechanism explaining improvement in endurance-related
measurements after concurrent training is increased maximum force, and/or increased
rate of force development (RFD) facilitating better blood flow to exercising muscles
(Hoff et al., 1999, 2002; Støren et al., 2008; Sunde et al., 2010; Aagaard et al., 2011).
Increases in RFD is often caused by increased neural activation and both heavy strength
training with maximal velocity in the concentric phase of the lift and explosive strength
training can increase neural activation (Mikkola et al. 2011). Superior improvement in
maximum force and RFD was accompanied by superior improvement in exercise
economy (Heggelund et al., 2013). Improvement in maximum force and/or RFD might
lower the relative exercise intensity and induce less constriction of the blood flow.
Alternatively, improved RFD may reduce time to reach the desired force in each
movement cycle. A shorter contraction time or shorter time with relative high force
production in working muscles may increase blood flow to the muscles by reducing time
where blood flow is restricted. Whether blood flow is enhanced after a period of
concurrent training has not been thoroughly investigated, but in theory an increase in
blood flow will increase delivery of O2 and substrates to the working muscles-
contributing to enhanced endurance performance (but not necessarily improved exercise
economy).On the other hand, a recent study on moderately trained cyclists by Barrett-
O`Keefe et al. (2012), showed that 8 weeks of heavy strength training improved work
economy at a cadence of 60 rpm, reduced muscular blood flow, while maintaining
muscular arterial-venous oxygen difference. The latter indicates that improvement in
muscular efficiency is an important mechanism behind improved work economy and
improved endurance performance.
Magnetic resonance imaging indicates that increased maximum strength reduces the
amount of activated muscle mass to generate the same absolute submaximal power
(Ploutz et al., 1994). If less muscle mass generates the same power after increased
maximum strength, metabolic strain is concentrated on fewer fibres and obviates the
effect of increased maximum strength. In the opposite direction, activated muscle fibres
might exercise at the same relative intensity due to the increase in maximum strength. If
that is the case, then the strength training would presumably not affect exercise economy
directly, measured as oxygen consumption, but potentially increase the endurance
performance via increasing the quantity of fresh muscle mass available when the final
sprint is approaching. In a time-trial setting, where the objective is to cover a certain
distance as fast as possible, this adaptation could theoretically result in superior
performance, due to increased power output per unit muscle mass.
One of the distinct differences between cycling and running is the stretch-shortening
cycle in running, while the leg movements in cycling are mainly composed of concentric
muscle actions. Thus, cyclists are not able to store energy during an eccentric phase and
utilize it in the subsequent concentric phase to the same extent as runners. It is estimated
that storage and return of elastic energy during running approximates about half of the
mechanical work performed during the eccentric phase of a running stride (Cavagna et
al., 1964).In accordance with the latter assertion, stiffness of the musculoskeletal system
in the lower-body is associated with enhanced running economy in a wide range of
runners (Craib et al., 1996; Jones, 2002; Trehearn & Buresh, 2009). Muscle-tendon
system is able to increase its stiffness through both explosive strength training (Foure et
al., 2011) and heavy strength training (Kubo et al., 2001, 2002). Furthermore, stiffness
increases in the muscle-tendon system of the lower-body after adding both heavy
strength training (Millet et al., 2002) and explosive strength training (Spurrs et al., 2003)
to the ongoing endurance training. Importantly, it is likely that there may be an
individual optimal stiffness in the muscle-tendon system. There are apparent advantages
of stiff tendons in some cases and compliant tendons in other cases (Fletcher et al.,
2010). Improved utilization of elastic energy in the muscle-tendon system in the lower-
body would reduce the demand of ATP production even at low submaximal running
intensities, thus improving running economy as observed in the majority of the presented
studies. This mechanism is unlikely to be equally important when cycling, due to the
lack of pronounced eccentric phase from which the elastic energy can be utilized.
Potential negative outcomes
A potential counterproductive outcome of strength training is that muscle hypertrophy
could have a negative impact on weight-bearing endurance events. An increase in
myofiber cross-sectional area could reduce capillary to muscle fibre cross-sectional area
ratio, thus increasing diffusion distance. In this respect, it is worth mentioning that 8-16
weeks of supplemental strength training failed to increase total body mass nor
compromise the development of VO2max in endurance athletes including cyclists (Bishop
et al., 1999; Bastiaans et al., 2001; Levin et al., 2009; Rønnestad et al., 20010a, 2010b;
Sunde et al., 2010; Aagaard et al., 2011), runners (Johnston et al., 1997; Paavolainen et
al., 1999; Spurrs et al., 2003; Turner et al., 2003; Saunders et al., 2006; Mikkola et al.,
2007a, 2011; Storen et al., 2008;), duathletes and triathletes (Hickson et al., 1988; Millet
et al., 2002) and cross-country skiers (Hoff et al., 1999, 2002; Osteras et al., 2002;
Mikkola et al., 2007b; Losnegard et al., 2011; Rønnestad et al., 2012).
Even though strength training can be added to endurance training without a concomitant
increase in total body mass, there seems to be a small, ~3-6%, increase in measurements
of muscle hypertrophy of the main target muscles (Rønnestad et al., 2010a, 2012;
Taipale et al., 2010; Losnegard et al., 2011; Aagaard et al., 2011). An impaired
hypertrophic response to strength training is likely explained by recent developments
within molecular sports science. Endurance exercise may negatively affect intracellular
pathways important for myofibrillar protein synthesis (reviewed in Hawley 2009).
Activation of adenosine monophosphate-activated protein kinase (AMPK) by endurance
exercise may inhibit mammalian target of rapamycin (mTOR) signalling and suppress
strength exercise-induced myofibrillar protein synthesis (Nader, 2006; Hawley, 2009).
Consequently, acute intracellular signalling response to concurrent strength and
endurance training does not promote ideal activation of pathways responsible for muscle
hypertrophy (Coffey et al., 2009). Observations of disparate mRNA response to
concurrent strength and endurance training underline the importance of local factors in
explaining compromised strength training adaptations to a large volume of concurrent
training (Coffey et al., 2009).
The observed impaired or absence of whole muscle or muscle fibre hypertrophy after
combining strength training with large volumes of endurance training (Hickson et al.,
1988; Bishop et al., 1999; Rønnestad et al. 2010a, 2012, 2012b; Losnegard et al., 2011;
Aagaard et al. 2011) greatly reduces the risk of impaired capillary to muscle fibre ratio.
In untrained subjects, strength training alone can increase some aspects of the capillaries
perfusing skeletal muscle fibres (Hather et al., 1991; McCall et al., 1996; Green et al.,
1999). In moderate trained students an increase in capillary to fibre ratio has been
observed after concurrent strength and endurance training, while no change was evident
after strength or endurance training alone (Bell et al., 2000). The only study performed
on top-level endurance athletes did not observe a negative effect after 16 weeks of
concurrent heavy strength training and endurance training on muscle capillarization
(Aagaard et al., 2011). In addition, after a period of concurrent strength and endurance
training there is no impairment of the oxidative enzyme activity in endurance-trained
athletes (Hickson et al., 1988; Bishop et al., 1999; Bell et al., 2000). Thus, with regard to
muscle vascularization and oxidative potential, there seems to be no indications of
negative effect of strength training.
To increase the probability of improved endurance performance subsequent to a strength
training period, the strength training exercises should involve similar muscle groups and
imitate the sports specific movements. This advice is underpinned by adaptations in the
neural system (like optimal activation of the involved muscles) as well as structural
adaptations (like optimising the number of active cross-bridges in that particular range of
motion). An intended rather than the actual velocity appears to determine the velocity-
specific training response (Behm & Sale, 1993; Heggelund et al., 2013). This scenario
means that even though the actual movement velocity is quite low, RFD might be
increased if the athlete focuses on performing the concentric phase of the lift as quick as
possible. Superior adaptations in maximal strength and RFD are achievable after 8
weeks of heavy strength training with maximal velocity in the concentric phase
compared to moderate velocity in the concentric phase (Heggelund et al., 2013). This
superiority was accompanied by superior improvement in exercise economy during
single leg knee-extension in untrained to moderate trained persons. Athletes are advised
to build up maximal strength in the important muscles during the preparatory period.
Two strength training sessions per week, designed as a ‘‘daily undulating periodized
program’’ is typically enough to achieve a sufficient increase in strength during a 12-
week period. Athletes are advised to perform between 4RM and 10RM and 2-3 sets with
approximately 2-3 min of rest between sets. Before endurance athletes start lifting heavy
loads they must ensure that they have first developed a proper lifting technique with
lighter loads. Note that in the beginning of a strength training period, it is common to get
“heavy” and “sore” legs in the first days after the strength training session. Therefore, it
is important to commence at low level with the concurrent endurance training during the
first two to three weeks of a strength-training program. One approach to overcome this
initial strength training adaptation phase is to conduct it just after the end of a
competition season, when endurance training has a lower priority. During the
competitive season or in training periods development of strength is not prioritized,
approximately one strength training session per week (low volume) with high intensity
seems to maintain the previous strength training adaptations (Rønnestad et al., 2010b;
Both explosive and maximal strength training have positive influences on endurance
running performance and/or running economy in endurance athletes (e.g. Paavolainen et
al., 1999; Millet et al., 2002; Spurrs et al., 2003; Støren et al., 2008). Recently, the
enhancing effects of combining endurance training with either heavy or explosive
strength training on running performance have been investigated. The studies that report
a difference in adaptations after heavy or explosive strength training point towards more
favorable adaptations as a result of heavy strength training (Guglielmo et al., 2009;
Mikkola et al., 2011, Barnes et al. 2013).
Recent research on highly trained athletes indicates that strength training can be
successfully prescribed to enhance endurance performance (Table I). For cycling
performance, heavy strength training with maximal velocity during the concentric phase
is preferred, while both heavy strength training with maximal velocity during the
concentric phase and explosive strength training have additive effects on running
performance. The primary explanation for improved endurance performance is most
likely adaptations within the strength trained muscle including postponed activation of
less efficient type II fibres, improved neuromuscular efficiency, conversion of fast-
twitch type IIX fibres into more fatigue resistant type IIA fibres, and improved
musculotendinous stiffness. Importantly, no negative effects of adding strength training
to an endurance training program have been reported.
The effects of strength training on endurance athletic performance have been the subject
of a long debate among athletes, coaches and sport scientists. Incorporation of strength
training in endurance athletes’ preparation has gradually received more attention during
the last two decades with studies showing divergent findings. Some of this discrepancy
seems to be related to the mode of strength training. In general a coach and athlete can
employ with confidence concurrent endurance and strength training to improve athletic
endurance performance. To optimize the effect of added strength training to cycling
performance, athletes should undertake heavy strength training with maximal velocity
during the concentric phase should be the training mode to recommend (instead of
explosive strength training), while both explosive- and heavy strength training with
maximal velocity during the concentric phase appear to have an additive effect on
The authors gratefully acknowledge the editorial comments and suggestions made by Prof.
David Pyne (Physiology, Australian Institute of Sport) in the preparation of this manuscript. No
sources of funding were used to assist in the preparation of this article. The authors have no
conflicts of interest that are directly relevant to the content of this article.
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Table I. Effects of heavy and explosive strength training on endurance performance.
benefit Potential negative
Improved VO2max No Increased body
economy Yes Compromised
relative VO2max No
capacity Yes Increased diffusion
threshold Yes Reduced
Reduced or delayed
fatigue Yes Reduced oxidative
enzyme activity No
Improved rate of
force development Yes