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Sport Sciences for HealthFounded by the Faculty of ExerciseScience - University of Milan, officialjournal of the Italian Society of Exerciseand Sport Sciences ISSN 1824-7490Volume 10Number 2 Sport Sci Health (2014) 10:61-66DOI 10.1007/s11332-014-0174-0

Uphill sprint vs. intermittent running inyoung soccer players: acute physiologicalresponses

Gianfranco Ibba, Fabio Pizzolato, RoccoDi Michele, Marco Scorcu, GiuseppeAttene, Giorgos Paradisis, Pablo Anon,Karim Chamari, et al.

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ORIGINAL ARTICLE

Uphill sprint vs. intermittent running in young soccer players:acute physiological responses

Gianfranco Ibba • Fabio Pizzolato • Rocco Di Michele • Marco Scorcu •

Giuseppe Attene • Giorgos Paradisis • Pablo Anon • Karim Chamari •

Johnny Padulo

Received: 18 September 2013 / Accepted: 10 February 2014 / Published online: 7 March 2014

� Springer-Verlag Italia 2014

Abstract

Purpose This study aimed to compare the acute effects of

uphill repeated sprinting ‘‘with long recovery’’ (RS) and

uphill intermittent running (IR) training on heart rate (HR)

and blood lactate (BL) responses.

Methods Thirteen young male soccer players randomly

performed in two separate occasions, on a slope (10 %), an

RS and an IR session. RS consisted of three sets of eight

maximal uphill 20-m sprints with long (90 s) recovery

between sprints, and 8 min passive rest between sets,

whereas IR consisted of 24 repetitions of 22-m sub-maxi-

mal (95 % of maximum speed achieved in an incremental

test) uphill runs interspersed by a 15-s downhill walking

recovery, lasting for a total duration of 8 min.

Results The mean HR, expressed as the percentage of

HRMAX, was significantly higher in IR than in RS

(86.1 ± 3.1 vs. 77.0 ± 4.5 %, respectively, p \ 0.05).

Conversely, BL measured after 3 min was significantly

higher in RS (5.9 ± 1.1 mmol L-1) than in IR (2.9 ± 1.2

mmol L-1, p \ 0.05).

Conclusions The differences found between RS and IR

may be attributed to the different work/recovery ratios and

speed characteristics. Therefore, uphill IR seems more

suitable when the target is to tax the aerobic system, while

RS may be more suitable when the focus is on stimulating

the speed without increasing the metabolic demand.

Keywords Exercise � Fitness � Performance � Team

sports � Uphill training

Introduction

Match analysis studies have demonstrated that soccer

requires repetitions of maximal or near-maximal sprints

with recovery periods of different durations [1, 2]. For this

G. Ibba � M. Scorcu

Cagliari Calcio Spa, Cagliari, Italy

G. Ibba

Laboratory of Physiology of Sport, Department of Medical

Sciences, University of Cagliari, Cagliari, Italy

F. Pizzolato

Department of Neurological and Movement Science,

University of Verona, Verona, Italy

R. Di Michele

Department of Biomedical and Neuromotor Sciences,

University of Bologna, Bologna, Italy

G. Attene

Faculty Medicine and Surgery, University of Cagliari,

Cagliari, Italy

G. Paradisis

Faculty of Physical Education and Sport Science,

University of Athens, Athens, Greece

P. Anon

High Performance Sports Graduate Program, Faculty of Social

Science, Lomas de Zamora National University, Buenos Aires,

Argentina

K. Chamari

Athlete Health and Performance Research Centre, ASPETAR,

Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar

J. Padulo (&)

Tunisian Research Laboratory ‘‘Sports Performance

Optimization’’ National Center of Medicine and Science

in Sport, Tunis, Tunisia

e-mail: sportcinetic@gmail.com

123

Sport Sci Health (2014) 10:61–66

DOI 10.1007/s11332-014-0174-0

Author's personal copy

reason, it has been established that the energy cost of

playing team sports is related to the specificity of the game

[3–5]. In this context, soccer has been described as a sport

requiring a high number of changes of activity and direc-

tion during the match [6, 7]. Consequently, patterns of

effort in intermittent shuttle running [8, 9] or repeated

sprint training [10, 11] have been proposed to improve

soccer players’ performance or used for talent selection

[12, 13]. In order to meet the requirements of the perfor-

mance model for soccer, several authors [14, 15] have also

codified training protocols according to the ability of per-

forming repeated sprints (repeated sprint ability, RSA),

because such ability was suggested to be a key factor of

performance in soccer [15].

RSA training [16, 17] in soccer players is aimed at

improving the ability to keep sprinting performance rela-

tively unchanged over a certain time period [18, 19].

However, other authors gave more importance to the

intermittent running training because it has been shown

that this training regimen improves aerobic fitness in soccer

players with less solicitation of muscle strength compared

to RSA training [20, 21]. Intermittent training allows to

reproduce high-intensity effort patterns close to the typical

intermittent actions of a soccer game [22]. The actions

performed by soccer players during play (e.g. accelera-

tions, decelerations, changes of direction) require high

muscular work [23] and alteration of the running gait [24].

In order to improve the muscle characteristics required by

the above-mentioned actions, uphill running is frequently

used as a specific training method in runners [25].

In this context, uphill running is a widely used method

particularly because it is performed in field, having there-

fore good ecological validity [26, 27]. Using uphill training

requires to specifically set the slope incline [25] and the

recovery between the sets, given the important effects of

these parameters on the energy cost [28] and muscular

work [28, 29]. Some authors have recommended a 10 %

uphill running as an optimal set to stimulate high muscle

work and therefore induce an increase in muscle strength

[27]. Besides, in uphill running [30] at lower (intermittent

running) or higher speed (maximal sprint) the muscular

work is different during the contact time [26, 31]. There-

fore, the uphill training used in team sports players could

induce different metabolic demands depending on whether

maximal sprinting or intermittent running is performed.

In this regard, little attention has been given to the

physiological effects of uphill running training in soccer

players [32]. Considering the consolidated use of both

intermittent running and repeated sprint training in soccer

players [32], it is of great interest to understand how, in

uphill training (10 %) the metabolic demand differs

between maximal sprint (with long recovery) and inter-

mittent running. Therefore, the aim of this study was to

analyse the heart rate and blood lactate responses during

repeated sprinting and intermittent running performed

uphill by young soccer players.

Materials and methods

Participants

Thirteen male soccer players were recruited from a junior

soccer team. Their (mean ± SD) age, body height, and

body weight were, respectively: 15.85 ± 0.38 years,

1.75 ± 0.05 m and 62.88 ± 4.81 kg. The mean soccer

training experience was 5.75 ± 1.23 years. At the time the

study was carried out, the players were participating in a

national youth league and performed about 8 h of training per

week. All the players performed habitually intermittent and

repeated sprinting training. All the participants were healthy,

without muscular, neurological and tendinous injuries.

The group was homogeneous with regard to the training

status. In the days before the present training sessions, light

training activities were performed, and strenuous endur-

ance and resistance training was avoided. Written consent

to participate was obtained from the participants’ parents/

guardians after being thoroughly informed of the study

design. All experimental procedures were approved by the

University Human Research Ethics Committee, which

followed the ethical standards of the Helsinki Declaration.

Experimental setting

On two separate days, after an incremental testing (INC-T)

session, all the participants performed an uphill repeated

sprinting and an uphill intermittent running training session

in a randomized order. The sessions took place within a

period of 15 days. Data were collected between 4 and 6

p.m. In the uphill training sessions, the average tempera-

ture, relative humidity and wind speed were, 17–19 �C,

56–66 %, and 0.10–0.15 m s-1, respectively. Before each

session, participants were instructed not to eat for at least

3 h before testing and not to drink coffee or beverages

containing caffeine for at least 8 h before the session

started.

In all the sessions, each participant completed a stan-

dardized 10-min warm-up wearing running shoes (Cate-

gory A3), which consisted of running at low speed

followed by 5 min of standardized active stretching exer-

cises. For the INC-T session, the warm-up also included

familiarization with the treadmill [33]. During the INC-T,

the heart rate (HR) was recorded by a Polar heart rate

monitor (Sport Tester; Polar Electro, Kempele, Finland)

which was fastened around the chest for continuous HR

recordings.

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In the INC-T session, maximum heart rate (HRMAX) was

determined using an incremental running test performed on

a motorized treadmill (Run Race Technogym� Run 500,

Gambettola, Italy) at a slope of 1 % [34–36]. The treadmill

speed was calibrated before each test, according to the

instructions of the manufacturer, and regularly checked

after the tests, in agreement with other studies [34–37].

After 3 min at 8 km h-1, the velocity was increased by

1 km h-1 every minute so that exhaustion was reached in

8 to 12 min for all subjects.

One week after the INC-T, outdoor sessions were per-

formed with 4 days of recovery in-between. All the sprints

were monitored with a photocell system (Brower Timing

System, Salt Lake City, UT, USA; accuracy of 0.01 s). The

test slopes were determined using a calibrated digital slope

indicator (R&B Manufacturing, Riverside, MO). Accord-

ing to manufacturer specifications, the digital level is

accurate within 0.1�. Training sessions were completed in

random order.

Intermittent running

After the standardized warm-up, the participants performed

intermittent running training (IR), consisting of 24 repeti-

tions of 22-m uphill (10 % slope) submaximal sprints, each

to be covered in a required time of 5 s (15.84 km h-1

corresponding to 95 % of the average maximum speed

achieved in INC-T). All the sprints were interspersed by

15 s of downhill walking recovery (5.28 km h-1 corre-

sponding to 32 % of the average maximum speed achieved

in INC-T) and had the same exercise-to-rest ratio (1:3)

[38]. The total session duration was 8 min. In each sprint,

the participants assumed the starting position and waited

for the start signal.

Repeated sprinting

All participants, after the standardized warm-up, performed

a repeated sprinting (RS) session, constituted by three sets

of eight uphill (10 % slope) 20-m fast sprints with long

recovery (90 s) between the sprints with the same exercise-

to-rest ratio (1:25) [38], and 8 min passive rest between the

sets. The mean sprinting time was 3.68 ± 0.39 s.

During both the sessions, HR was continuously mea-

sured with the Sport Tester monitor using a 1-s sampling

period. For the RS, the average HR of the three sets,

including the values recorded during the recovery periods

between sprints and excluding the values recorded during

the recovery periods between sets, was computed and used

for the further analyses. For the IR, the average HR value

of the entire 8-min period was considered. Blood lactate

(BL) concentration was measured 3 min after the last sprint

of each set in the RS session [39], and 3 min after the end

of the 8-min bout in the IR session [39]. The measures were

carried out by taking 5-lL blood samples from the fingertip

and analysing them using a Lactate Pro LT-1710t (ArkRay

Inc, Kyoto, Japan). For BL, the average of the three values

collected in the RS session was considered for the further

analysis.

Statistical analyses

All the data are reported as the mean ± standard deviation

(SD). After verifying the normality of the distribution, the

mean BL and HR values, respectively measured in the IR

and RS, were compared with Student’s t tests for paired

data using SPSS 15.0 (IBM Corp., Somers, NY, USA).

Significance was set at p B 0.05.

Results

The maximum velocity achieved in the incremental run-

ning test was 16.6 ± 1.2 km h-1. HRMAX was 188 ± 7

beats min-1. All the athletes showed a lower HR in the RS

(145 ± 6 beats min-1) when compared to IR (162 ± 8

beats min-1). The mean HR, expressed as the percentage

of HRMAX, was significantly higher in IR than in RS

(86.1 ± 3.1 vs. 77.0 ± 4.5 %, p \ 0.05), with differences

ranging from 2 to 14 % (Fig. 1a). On the contrary, BL was

significantly higher in RS (5.9 ± 1.1 mmol L-1) than in IR

(2.9 ± 1.2 mmol L21, p \ 0.05), with individual differ-

ences ranging from 0.3 to 4.6 mmol L-1 (Fig. 1b).

Discussion

The present study is the first to compare acute physiolog-

ical effects of two uphill training methods in young soccer

players. The results showed a significantly higher HR

(9.1 % difference when expressed as percentage (%) of

HRMAX), in intermittent running (IR) compared to repeated

sprints (RS), while the mean BL was more than twice

higher in RS. To the best of our knowledge, no research has

analysed the physiological responses to intermittent and

sprint running training performed uphill. IR is a common

training method in many team sports [32], and is performed

with several protocols and different modalities of volume,

intensity, and work:rest ratio [40]. For this reason, the

metabolic responses [41] to an IR session are strictly

dependent on the protocol used.

Uphill running is a popular method to develop the

acceleration phase of sprinting and specific strength of the

hip extensor muscles [27, 42, 43]. Moreover, many authors

investigated the effects of uphill running on the running

gait. Paradisis et al. [27], for instance, using combined

Sport Sci Health (2014) 10:61–66 63

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uphill and downhill sprint running showed an increased

maximum running speed (3.5 %) and step frequency

(3.4 %), while flight time (4.3 %) and contact time (3.3 %)

decreased. Another study of the same group [43] reported

similar results, and concluded that uphill and downhill

training are both more effective in improving maximal

running speed, compared to a horizontal sprint training

method. These changes were possible due to the decrease

of negative work [44] and shorter contact time, in contrast

[45–48] with the uphill training which involves a greater

positive work (12.2 %) and increased contact time (2.4 %)

[27, 29, 43]. Other studies focused on the kinetics and

kinematic analysis when running at different slopes [35], or

combining different slopes with different constant speed

runs [49] and lower limb muscle activity patterns [40, 50].

However, little attention has been given to the effects of

uphill training on the physiological demand in soccer

players.

The early studies of Astrand et al. [40] and Christensen

et al. [50] described the metabolic responses at different

intensities and work:rest ratios. Little information exists

concerning very short intermittent training (5 ? 15) at sub-

maximal intensities performed by young soccer players.

The majority of studies did focus on different relationships

between work and recovery: 15 ? 15, 30 ? 30; 60 ? 60,

240 ? 240; with 100–120 % VO2max intensity in different

sports and training methods [40]. In this study, the inter-

mittent protocol was performed at a running speed of

15.84 km h-1 (4.4 m s-1), which corresponds to 95 % of

the mean maximum speed obtained in the incremental test

(16.6 ± 1.2 km h-1). The distance covered in the two

training sessions was very similar, that is, 528 m in IR and

480 m in RS. In IR the mean blood lactate concentration

was 2.9 ± 1.2 mmol L-1, resulting similar to that reported

in other studies with intermittent short runs and active

recovery. Astrand et al. [40] observed that when a heavy

constant workload (350 W) was divided into short periods

of work and long periods of rest (30 and 90 s, respectively),

the load became sub-maximal from a metabolic point of

view, was tolerated for 1 h, and resulted in a final BL

concentration of 2.2 mmol L-1. Christensen et al. [50]

showed that the work ratios 1:2 and 1:4 resulted in a low BL

concentration that did not exceed 2 mmol L-1 along with

no severe fatigue perceived by the subjects. Moreover,

Christensen et al. [50] analysed two subjects performing

continuous running and various modalities of intermittent

runs in level treadmill at 20 km h-1. With short-duration

intermittent runs (5–10 s) at work:rest ratios of 1:1, 1:2 and

1:3, the subjects showed low BL (*2.5 mmol L-1) and

heart rate values.

This low concentration of lactate during IR can be

explained by the myoglobin functions as an oxygen store

with a buffering effect during short spells of heavy work. In

fact, during brief work intervals, the oxygen stored in

myoglobin can supply until half of energy requirement and

myoglobin stores reload during rest/recovery. A further

explanation is the increase in adenosine triphosphate, cre-

atine phosphate and citrate levels during rest periods,

delaying glycolysis and decreasing glycogen depletion, and

allowing the utilization of creatine phosphate and oxygen

bound to myoglobin [22]. Conversely, in RS, the higher BL

was probably due to the effect of the high sprinting velocity

that required different energy sources [30, 51]. In fact, in

RS, the sprinting time was lower than 4 s [40]. For such

short sprints with relatively long recovery periods, the

principal source of energy is the ATP/PCr metabolic path-

way, but there is also a significant contribution of the gly-

colytic pathway, explaining the higher BL observed in RS

Fig. 1 Individual heart rate (HR, a), and blood lactate concentration

(BL, b) responses in the repeated sprint training (RS), and in the

intermittent running training (IR). The thick dashed line represents the

mean

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compared to IR, in which the glycolytic mechanism was

less involved due to the lower exercise intensity. During IR,

the HR was higher than what was shown in previous studies

for horizontal treadmill or cycle ergometer simulations

sessions [52]. These differences may be due to well-

described increased oxygen uptake during uphill running

compared to horizontal running [22]. The mean HR values

(86.1 ± 3.1 % HRMAX) were similar to those reported

previously in the literature for a soccer game in adults [6].

Indeed, the average exercise intensity, during a soccer game

is usually between 80 and 90 % of HRMAX [14], with mean

HR absolute values around 165 beats min-1, corresponding

to a relative metabolic load of about 75 % of the maximum

oxygen uptake [53]. The acute effects of uphill IR in the

present study are also similar to various endurance training

methods used for soccer players. Indeed, Brandes et al. [53]

showed similar physiological responses during small-sided

games (2 vs. 2, 3 vs. 3, 4 vs. 4) in elite young soccer players.

The mean HR response of the 4 vs. 4 format was around

90 % of HRMAX and the mean BL concentration was

4.4 mmol L-1. Conversely, in RS, the HR was lower

because the time of recovery was very large, thus allowing

the athletes a complete recovery, differently from what

happened in IR.

Practical application

In conclusion, IR performed uphill (10 % slope) at sub-

maximal intensity seems a useful training tool when the

goal is to stimulate HR while RS may be a more suitable

form of training when the focus is on stimulating glycolysis

and high-intensity muscle work.

Acknowledgments This study was not supported by any sources of

funding.

Conflict of interest Gianfranco Ibba, Fabio Pizzolato, Rocco Di

Michele, Marco Scorcu, Giuseppe Attene, Giorgos Paradisis, Pablo

Anon, Karim Chamari and Johnny Padulo declare they have no

conflict of interest.

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