Strength and Conditioning for Adolescent Endurance Runners

Abstract

For the adolescent athlete who chooses to specialize in endurance running, strength and conditioning (S&C) activities provide a means of enhancing several important determinants of performance and may reduce the risk of overuse injury. It is recommended that adolescent endurance runners include at least 2 S&C sessions per week that comprise movement skills training, plyometric and sprint training, resistance training, plus exercises designed to target specific tissues that are vulnerable to injury. This article describes how these modalities of training can be integrated into the routine of adolescent endurance runners.

Full text

Strength and Conditioning for Adolescent Endurance Runners

Strength and Conditioning for Adolescent Endurance Runners
ABSTRACT
For the adolescent athlete who chooses to specialize in endurance running, strength and conditioning
(S&C) activities provide a means of enhancing several important determinants of performance and may
reduce the risk of overuse injury. It is recommended that adolescent endurance runners include at least
two S&C sessions per week that comprise of movement skills training, plyometric and sprint training,
resistance training, plus exercises designed to target specific tissues that are vulnerable to injury. This
article describes how these modalities of training can be integrated into the routine of adolescent
endurance runners.
Key words: paediatric, endurance, distance running, youth, concurrent training
INTRODUCTION
Endurance running is a popular choice of sport for young athletes. For example, in 2016-17, cross-
country was the fourth and fifth largest sport by participation for boys and girls respectively in USA
high schools (see www.nfhs.org/ParticipationStatistics), and endurance running represented the second
most popular sport (18.7%) in a survey (n=7794) of Scandanvian 14 year olds (83). A young athlete
should be exposed to a wide range of sports and physical activities during their adolescence, however
the priority should be placed on the development of rudimentary motor skills and muscular strength
(49). Endurance training during early-adolescence (11-14 years old) should form part of an active
healthy lifestyle but should not take precedence over other modalities of sport-training (80). Endurance
sports are typically associated with a high volume of training (80), which places the developing body
of a young athlete under a high level of stress that could leave them susceptible to overtraining
syndrome, illness and overuse injury (54). Therefore, specialization in endurance running should not
occur until late-adolesence, when a young athlete’s body is sufficiently mature and well-conditioned to
cope with the rigours of this type of training. Strength and conditioning (S&C) activities might
contribute towards lowering the risk of injury in athletes (45, 82), therefore providing sport-specific
recommendations for this vulnerable population is important.
Endurance running is primarily limited by cardiovascular and metabolic factors, however there is an
abundance of research showing that strength training (ST) activities (resistance training (RT), explosive
resistance training (ERT) and plyometric training (PT)) can provide performance benefits to middle-
(0.8-3 km) and long-distance (>3 km) runners (16, 29). A plethora of literature also exists that

demonstrates ST activities are also a safe and effective way of enhancing proxy measures of athletic
performance in adolescents of both sexes (10, 41, 46). Specifically, compared to sport-only training,
various forms of ST augment improvements in maximal strength, explosive strength, muscular
endurance, sprint speed, agility test time, tennis serve velocity, kicking velocity, throwing velocity, and
general motor skills (10, 40, 41, 46). However, there are currently no papers which have specifically
summarized the effect of ST modalities on aerobic-related qualities in young athletes. For practitioners
working with young distance runners in particular, it would be useful to establish whether ST activities
offer any benefit to performance-related factors and how such training techniques could be applied in
practice. Therefore, the aims of this article are to briefly review the literature that has investigated the
efficacy of ST on the determinants of endurance running in adolescent runners, and provide guidelines
for best practice to improve performance and minimize the ocurrence of overuse injury.
Figure 1. Primary determinants of endurance running performance and the modalities of training to
improve each. V
̇O2max = maximal oxygen uptake, sV
̇O2max = speed at maximal oxygen uptake.
DETERMINANTS OF ENDURANCE RUNNING PERFORMANCE
Endurance running performance is determined by several key physiological variables, which are
summarized in figure 1. The physiological determinants of performance for adolescents appears to be
similar to those of adult runners (3, 27). A number of investigations have confirmed that maximal

oxygen uptake (V
̇O2max) is a significant predictor (r=0.5-0.9) of performance for 1.5 km (1, 3), 3 km (1,
50, 87), 5 km (1, 27) and cross-country (24, 34) in young (10-18 years) groups of runners. The
proportion of V
̇O2max that can be sustained for a given duration (known as ‘fractional utilization’), has
also been shown to significantly correlate with endurance running performance in adolescents (50, 87).
Running economy (RE), defined as the metabolic cost of running a given distance (79), is related to
middle- (3, 87) and long-distance running performance (24, 34), and importantly, is influenced by
neuromuscular related qualities, which can potentially be improved with ST activities (16, 29).
Additionally, speed at V
̇O2max, which is a product of V
̇O2max and RE, correlates well with distance
running performance in adolescents (1, 3, 24, 27).
The contribution of anaerobic factors to endurance running performance in adults is well-established
(20), however the influence of anaerobic determinants on performance in young endurance runners has
not been fully delineated. This is likely due to the unspecific nature of the tests (Wingate test, isokinetic
strength tests, counter-movement jump height) utilized to quantify anaerobic and neuromuscular
capacities in studies that have investigated young distance runners (3, 24, 28). Anaerobic capacity and
neuromuscular capabilities are thought to play a large role in discriminating performance in runners
who are closely matched from an aerobic perspective (22, 67). Mahon and co-authors (50) also showed
that 55 m sprint and counter-movement jump were significant predictors of 3 km time trial in
preadolescent children, although given the age of the participants, this finding could simply be a
reflection of individuals possessing high or low levels of athletic ability across the range of the tests
utilized. Speed at V
̇O2max probably provides the most sport-specific representation of neuromuscular
capabilities in distance runners, however measures of maximal running speed and anaerobic capacity
are also important attributes (65). For an 800 m specialist in particular, near-maximal velocities of
running are reached during the first 200 m of the race (74), which necessitates a high capacity of the
neuromuscular and anaerobic system. Similarly, the quickest finisher at the end of a middle- or long-
distance race often determines the winner (85), thus possessing a higher top speed is potentially crucial
for achieving success in distance running. Regardless of the capacity for anaerobic and neuromuscular
factors to predict endurance performance in adolescents, activities to develop sprint speed and muscular
strength-qualities as part of a well-rounded physical training programme is recommended during
adolescence irrespective of whether sport-specialization has occurred (47, 49).
EFFECT OF STRENGTH TRAINING ON AEROBIC-RELATED PARAMETERS
Based upon the findings of recent reviews (16, 29), it is suggested that supplementing the training of an
endurance runner with ST is likely to provide improvements in RE, time-trial (1.5 km – 10 km)
performance and anaerobic parameters such as maximal sprint speed. Improvements in RE in the
absence of changes in V
̇O2max, speed at V
̇O2max, blood lactate and body composition parameters suggests

that the underlying mechanisms predominantly relate to alterations in intra-muscular co-ordination and
increases in stiffness (16). Specifically, ST brings about increases in motor unit recruitment, firing
frequency and musculotendinous stiffness, which are thought to optimize the length-tension and force-
velocity relationships of active skeletal muscle, thus reducing the metabolic cost of running (36). It is
clear that the inclusion of ST also does not adversely affect V
̇O2max, blood lactate markers or body
composition (16). Concurrently, RE showed improvements of 2-8% with ST compared to a running-
only control group following a 6-14 week intervention that includes 2-3 ST sessions per week (16).
Efficacy in Adolescent Runners
Three studies have investigated the effect of ST specifically in young (<18 years) middle- or long-
distance runners and these are summarized in table 1. A recent study by Blagrove et al. (17) found that
two weekly sessions of ST (mainly PT and RT) added to the programme of post-pubertal adolescent
distance runners (17 years) for ten weeks was ‘possibly beneficial’ for RE (effect size: 0.31-0.51) and
‘highly likley beneficial’ for maximal sprint speed. However, only the maximal speed improvement
reached statistical significance (p<0.05) compared to the change observed in the control group. Mikkola
et al. (58) took a group of trained male and female distance runners (mean: 17 years, V
̇O2max: 62.5
mL.kg-1.min-1) and following eight weeks of ERT, PT and sprint training, noted a difference (-2.7%) in
RE at 14 km.h-1 and improvements in anaerobic capabilities (speed during the maximal anaerobic
running test and 30 m sprint) compared to a running-only group. It is noteworthy that both of these
investigations (17, 58) included sprints (3-10 x 30-150 m) as part of the intervention, which provides a
highly specific overload to the neuromuscular system in endurance runners. Interestingly, participants
in the ST intervention groups in these studies reduced their weekly running volume to accommodate
the additional S&C activities. Total time spent training was however very similar between intervention
and control groups.
Bluett and associates (18) found that ten weeks of concurrent aerobic and ST provided little strength
advantage and no change in 3 km time trial performance in 10-13 year old competitive runners
compared to running only. This study utilized mainly single joint machine-based RT and did not
measure any physiological parameters, which may explain the lack of effect observed. The authors
speculated that excessive fatigue resulting from the concurrent training regimen may have compromised
both strength and endurance adaptations (18). Interestingly, the blunting of strength adaptation which
is often observed in adult performers when both strength- and endurance-training are included in the
same training session (90) appears not to occur in children (53) and adolescents (75, 76). As the
interference phenomeon is mediated by training volume and recovery from sessions (5), it seems likely
that the volumes of each training modality included in the aforementioned studies were insufficient to
negatively impact upon strength-related adaptation. Indeed, in elite youth soccer players (17 years) who

utilize higher workloads compared to younger performers, larger improvements were evident in
strength and sprint performance after five weeks when ST was performed after sport-specific endurance
training on two days per week, compared to a group who adopted a ST followed by endurance training
sequence (33).

Authors
Participants
n (I/C), sex, age
Study
duration
Running volume
ST
frequency
ST prescription
Main strength
outcomes
Main running-related
outcomes
Blagrove
et al. (18)
18 (9/9), both,
17.2 years
10
I: 151 min.wk-1
C: 213 min.wk-1
2 per
week
PT (3-4 x 6-8/15 m): box
jumps, A-skips, hurdle
jumps
RT (2-3 x 6-8 reps): back
squat, RDL, rack pull,
deadlift, step-ups, leg
press, calf raise
MVC (15.4%,
ES=0.86, p<0.05),
vGRFjump (6.1%,
ES=0.93)
CMJ, little
difference
compared to C
RE@ sLTP (3.2%,
ES=0.31), sLTP -1 km.h-1
(3.7%, ES=0.47), sLTP -2
km.h-1 (3.6%, ES=0.51)
20 m sprint (3.6%, ES=0.32,
p<0.05)
Bluett et
al (19)
12 (6/6), both,
10-13 years
10
Both groups: 2 x
runs per week
(1x25-30 min
continuous,
1xintervals)
2 per
week
RT (3-4 sets x 10-12
reps): leg curl, leg
extension, leg press,
upper limb/trunk
exercises
Increase (12.2-
24%) loads lifted
during ST but no
change in peak
torque pre-post I
3 km TT no change in either
group
Mikkola
et al (59)
25 (13/12), both,
17.3 years
8
I: 8.8 h.wk-1
(19% running
replaced with
ST),
C: 8.5 h.wk-1
3 per
week
PT: alternative jumps, calf
jumps, squat jumps,
hurdle jumps
ERT (2-3 x 6-10 reps):
half-squats, knee
extension, knee flexion,
leg press, calf raise
MVC (8%), 1RM
(4%), RFD (31%)
on leg press; all
p<0.05.
CMJ and 5-bounds
little difference
compared to C
RE@14 km.h-1 (2.7%,
ES=0.32, p<0.05),
@10,12,13 km.h-1, NS
BL@12 km.h-1 (12%,
p<0.05), @14 km.h-1 (11%,
p<0.05)
sMART (3.0%, p<0.01), s30
m sprint (1.1%, p<0.01)
C=control, I=intervention, ST=strength training, wk=week, PT=plyometric training, RT=resistance training, RDL=Romanian deadlift, MVC=maximum
voluntary contraction, ES=effect size, vGRFjump=vertical ground reaction force during squat jump, CMJ=counter-movement jump, RE=running economy,
sLTP=speed at lactate turnpoint, TT=time trial, ERT=explosive resistance training, 1RM=one repetition maximum, RFD=rate of force development, NS=not
statistically significant, BL=blood lactate
Table 1. Summary of studies (n=3) that have investigated the effects of a strength training intervention on adolescent endurance runners.

Research investigating the impact of ST techniques on performance-related measures in young athletes
has tended to use participants from field-based sports, martial arts, court sports, aquatic sports,
gymnastics and strength-based sports (40, 46). A number of studies using adolescent participants from
other sports that require high-levels of aerobic fitness have observed superior improvements in Yo-Yo
test (44, 51, 72, 91) and middle-distance time-trial performance (70, 73) after various modalities of ST
were added (6-12 weeks) to a sports-specific training programme, compared to only practicing the sport.
Taken together, it appears that the addition of 2-3 ST sessions to the weekly routine of adolescent
endurance runners provides a small but potentially meaningful benefit to RE and maximal sprint speed
following an 8-10 week intervention. Evidence for improvements in performance exists for adult
runners (16), however there is currently a lack of research in younger endurance runners. Benefits are
likely to be larger for interventions of a longer duration (29) and for ST programmes that are supervised
by qualified practitioners (16). Although the majority of studies in adults supplement a runners training
with ST, there also appears to be no disadvantage to reducing weekly running volume to accommodate
the addition of two weekly ST sessions.
PRACTICAL RECOMMENDATIONS
Timing of Specialization and Long-Term Athlete Development
Adolescence represents an important period of development in young athletes where significant
alterations in hormonal status causes rapid physical growth (52). Contemporary views of long-term
youth development suggest adolescents should avoid training routines that focus on intensive training
in a single sport (for >8 months per year), or a total weekly training volume (in hours) that exceeds the
athletes age in years, until late-adolescence (47, 49, 63). Evidence from several endurance sports shows
elite senior athletes tend to specialize at a later age, and participate in a diverse range of sports during
their earlier years (26, 60). Recent work has also shown that very few middle-distance runners ranked
in the UK top 20 in the under-13 and under-15 age-groups experience success as senior runners (43).
Young athletes who adopt an early-diversification, late-specialization approach to their development
have fewer injuries, are at less risk of overtraining, and play sports longer than those who specialize in
one sport before puberty (21, 30).
The youth athlete development model suggests a wide range of physical activities and training
modalities should be utilized during adolescence, however movement skills training (MST) and
development of strength qualities should be prioritized (47, 49). The emphasis on ST activities
throughout an athletes development is thought to maximize adaptations to inter- and intra-muscular
coordination, during a period when neuroplasticity is high (64). Improvements in muscular strength and
motor control during this period have also been shown to improve physical performance (10, 46) and

lower the risk of sustaining an injury (62, 82). It is recommended that endurance training (and metabolic
conditioning) is not emphasised, relative to other biomotor abilities, until late-adolescence (49), as
typically this type of training is associated with high volumes of work, which may lead to injury or
overtraining (54). Moreover, pre-pubertal children have tended to show smaller changes (<10%) in
aerobic measures following endurance training interventions compared to post-pubertal adolescents and
adults (54, 56). A recent study also showed that pre-pubertal boys (11 years) were metabolically
comparable to well-trained endurance athletes and experienced less fatigue during high-intensity
exercise compared to untrained adults (14). It was suggested that pre-pubertal children avoid specific
training to develop aerobic metabolic qualities and shift priority during post-pubertal years once
movement technique and mechanical competency have been developed (14). Due to the risks associated
with early-specialization, it is recommended that adolescent athletes younger than 15 years old do not
solely specialize in endurance running, but should participate in a wide range of sports and physical
activities, including ST.
Organization of the Training Microcycle
Prior to specialization in a sport of a young athletes choice, physical training should be semi-structured
and not emphasize peaking for competitions (26, 63). Conversely, an adolescent endurance runner will
typically run 45 to 55 miles weekly in preparation for a race (80), which when combined with academic
and social commitments, can place a high level of physical and psychological stress on a young athlete
(54). This necessitates a well-organized approach to training that caters to the needs of individual
athletes and ensures sufficient periods of recovery between bouts of training.
Two seven-day microcycle designs are shown in Table 2a and 2b to illustrate how an adolescent
endurance runner could incorporate S&C activities into their routine. Adolescent distance runners
typically perform 2-3 high-intensity running sessions per week (15), and these should form the priority
sessions in the programme (Table 2a and 2b; Tuesday, Thursday and Saturday). Similarly, a minimum
of two ST sessions per week are suggested for adolescents (11, 48) and endurance runners (16). RT
sessions should ideally take place at least three hours after a running session (6) and at least 24 hours
recovery should follow after ST before an intensive running session (31). A novel approach to
organizing S&C activities around training and lifestyle commitments with young runners is to
incorporate shorter periods of activity (‘training units’) as part of running sessions wherever possible
(see Table 2b). This type of programming is useful for young runners who perhaps cannot access a
specialist S&C facility, and therefore perform a largely home-based routine, or are unable to commit to
two full S&C sessions per week. Each training unit takes 10-20 min to complete, thus making it easy to
integrate some purposeful S&C prior to or after running sessions. It is important to note that studies in

adolescent distance runners (17, 58) have shown that including weekly ST sessions are more effective
than increasing running volume, at least in the short-term (8-10 weeks).
Assuming runners are of a non-strength trained status, it appears that a variety of ST modalities can be
used to achieve similar outcomes. However to maximize long-term adaptations in young athletes, it is
suggested that a periodized approach is adopted with fundamental skills training and RT prioritized
initially (9, 25, 47). Figure 2 provides an overview of the session design and characteristics of specific
training units recommended for adolescent distance runners. A similar session design framework has
also been employed successfully in other investigations that used distance runners embarking upon a
ST programme for the first time (9, 17, 58).
Figure 2. Recommended structure of a strength and conditioning session for adolescent endurance
runners. Characteristics and example exercise prescription for individual training units are also shown.
Prescription is sets x repetitions (unless stated).

Day
Mon
Tues
Wed
Thurs
Fri
Sat
Sun
Session
(am) Easy 30 min
run
(pm) S&C session
Interval training
session
(am) Cycle or
swim 30 min
(pm) S&C session
Tempo run* (20-
30 min)
Rest
Race or interval
training session
Easy 45 min run
S&C = strength and conditioning. * Continuous fast run performed at approximately 10 km race-pace (speed at lactate turn-point)
Table 2a. Example of a seven day microcycle for an adolescent endurance runner.
Day
Mon
Tues
Wed
Thurs
Fri
Sat
Sun
Session
Easy 30 min run +
PT and RT
MST + Interval
training session
Cycle or swim 30
min + RT and SC
PT + Tempo run
(20-30 min)
Rest
Race or interval
training session +
SC
Easy 45 min run +
MST
PT = plyometric training, RT = resistance training, MST = movement skills training, SC = specific conditioning
Table 2b. Example of a seven day microcycle for an adolescent endurance runner with strength and conditioning activities organised as training units before
or after running sessions. Training units should last 10-20 min with the focus on movement quality rather than inducing high levels of fatigue.

Movement Skills Training
The inclusion of MST in the routine of adolescent distance runners is recommended, and is likely to
reduce long-term injury risk (45, 62, 82). This form of conditioning is ideal to include as part of a
movement preparation warm-up routine prior to running and ST sessions, or as an independent training
unit (82). MST should include activities to enhance both general (fundamental) and specific (running-
related) movement skill and control, balance and dynamic stability, and low-level resistance training
targeting specific muscle groups, such as the gluteals (37).
Plyometrics and Sprint Training
Low intensity plyometric-based exercise that aim to develop ankle stiffness, such as skipping, low-box
re-bound jumps, mini hurdle jumps and short range hopping tasks, offer a potent stimulus to the
neuromuscular system and have independently been shown to enhance RE and time trial performance
(12, 68, 71, 81, 86). It is suggested that 30-60 foot contacts per session are utilized initially with
adolescent distance runners (17). Sprint training has also been used in several investigations showing
enhancements in maximal speed and performance-related factors (17, 58, 59, 66). Three to five sets of
short distance (30-60 m) technical and maximal sprints performed 2-3 times per week is likely to provide
benefits to adolescent endurance runners.
Resistance Training
Resistance training, which should include both ERT and heavy RT, increases motor unit recruitment
and firing frequency, thus enhances a runners ability to appropriately control and express force during
ground contact. Although changes in fat-free mass appear to be minimal following a ST intervention in
distance runners (16), a targeted RT programme, that aims to increase muscle mass specifically around
the proximal region of the lower limb may enhance biomechanical and physiological factors, which
positively influence RE (36). Exercises, such as squats, deadlifts, step-ups and lunge patterns, which
possess similar kinematic characteristics to running gait, are likely to provide the greatest transfer (8)
and have been utilized in several previous investigations (9, 17, 58). Loaded jump squats, medicine ball
throwing and weightlifting are examples of suitable ERT activities that can also be utilized (8, 9, 59).
Upper limb exercises such as press-ups, rowing exercises and overhead presses, should also be
incorporated to offset the vertical angular momentum created by the lower limbs and aid in controlling
excessive rotation forces (42, 69, 77). One to three sets of each exercise performed in a moderate
repetition range (8-12 repetitions) is likely to provide non-strength trained individuals with a stimulus
sufficient to drive neuromuscular adaptation whilst developing skill in each exercise (9, 17, 59). Higher
loads (≥80% one repetition maximum) and lower repetition ranges (3-8 repetitions) are likely to be

required to provide further overload in strength-trained adolescents, with volume of work moderated
via an increase in sets.
Specific Conditioning
Many young endurance runners are motivated to include S&C activities to reduce injury risk more so
than improve their performance (15). Youth endurance athletes have been identified as a high-risk group
due to the rigorous training that they undertake during a critical period of their physical and emotional
development (54, 80). Indeed, injury incidence rate has been reported to be higher in adolescent elite
endurance runners compared to other endurance sports (88). Moreover, female adolescent runners tend
to display higher rates of low bone mineral density and bone stress injuries compared to young female
athletes in other sports (78). Overuse injuries occur over multiple running sessions when structure
specific cumulative load exceeds capacity (13). MST, PT and resistance-based exercises are likely to
contribute towards lowering risk of injury via enhancements in motor control and increased bone
mineral density and tissue resilience (45, 62, 89). Exercises designed to expose specific muscles or
tissues to a high magnitude of load are also likely to provide benefits to tendon stiffness (35) and
tolerance to repetitive stress (7, 19, 61, 84, 89). It is recommended that such exercises are positioned in
final part of a session or performed separately, as pre-fatiguing muscles in isolation is likely to be
detrimental to performance in multi-joint tasks (4). Specifically for distance runners, targeted
conditioning exercises should focus on the specific structures which are vulnerable to injury, or the
muscles that contribute towards controlling the positioning of joints within the lower limb, such as: the
intrinsic joints of the feet, the calf-Achilles complex, gluteal and hamstring muscles (2, 32, 38, 55, 57,
61). In addition, specific exercises that target proximal musculature around the lumbopelvic-hip
complex (‘core stability’) are likely to offset the risk of several types of common overuse injuries in
runners (23). Specifically, exercises which facilitate greater strength and control of the hip abductors
and external rotators are likely to provide benefits (23, 39).
CONCLUSION
Endurance running performance is constrained by several important physiological variables, however
anaerobic and neuromuscular factors have also been recognized as being important. For the young
athlete, participating in a broad range of sporting and physical pursuits is recommended during early-
adolescence. Age-appropriate S&C should form an integral part of a well-rounded approach to the long-
term physical development of all young sports performers. Participating in endurance running events
can certainly form part of a programme of activities during adolescence, however it is suggested young
athletes should not solely specialize in endurance running until late-adolescence. For the young

endurance runner, adding ST sessions twice per week that includes RT, PT and sprinting, is likely to
provide benefits to RE and maximal sprint speed that translate to improved performance. Moreover,
these activities, plus MST and specific strengthening of tissues vulnerable to injury, are important for
lowering the risk of overuse injury.

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