Aerobic endurance training improves soccer performance

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Aerobic endurance training improves soccer
Norwegian University of Science and Technology, Department of Sport Sciences, N-7491 Trondheim, NORWAY

          HELGERUD, J., L. C. ENGEN, U. WISLFF, and J. HOFF. Aerobic endurance training improves soccer performance. Med. Sci.
          Sports Exerc., Vol. 33, No. 11, 2001, pp. 19251931. Purpose: The aim of the present study was to study the effects of aerobic training
          on performance during soccer match and soccer specific tests. Methods: Nineteen male elite junior soccer players, age 18.1  0.8 yr,
          randomly assigned to the training group (N  9) and the control group (N  10) participated in the study. The specific aerobic training
          consisted of interval training, four times 4 min at 90 95% of maximal heart rate, with a 3-min jog in between, twice per week for 8
          wk. Players were monitored by video during two matches, one before and one after training. Results: In the training group: a) maximal
          oxygen uptake (V  O2max) increased from 58.1  4.5 mLkg1min1 to 64.3  3.9 mLkg1min1 (P  0.01); b) lactate threshold
          improved from 47.8  5.3 mLkg1min1 to 55.4  4.1 mLkg1min1 (P  0.01); c) running economy was also improved by 6.7%
          (P  0.05); d) distance covered during a match increased by 20% in the training group (P  0.01); e) number of sprints increased by
          100% (P  0.01); f) number of involvements with the ball increased by 24% (P  0.05); g) the average work intensity during a soccer
          match, measured as percent of maximal heart rate, was enhanced from 82.7  3.4% to 85.6  3.1% (P  0.05); and h) no changes
          were found in maximal vertical jumping height, strength, speed, kicking velocity, kicking precision, or quality of passes after the
          training period. The control group showed no changes in any of the tested parameters. Conclusion: Enhanced aerobic endurance in
          soccer players improved soccer performance by increasing the distance covered, enhancing work intensity, and increasing the number
          of sprints and involvements with the ball during a match. Key Words: V  O2max, LACTATE THRESHOLD, RUNNING ECONOMY,

       occer is one of the most widely played and complex                        tween the top team and a lower placed team in the Norwe-
       sports in the world, where players need technical,                        gian elite division.
       tactical, and physical skills to succeed. However,                           A professional soccer player should ideally be able to
studies to improve soccer performance have often focused                         maintain a high level of intensity throughout the whole
on technique and tactics at the expense of physical resources                    game. Some studies, however, have shown a reduction in
such as endurance, strength, and speed.                                          distance covered, a lower fractional work intensity, reduced
   The average work intensity, measured as percent of max-                       fc, reduced blood sugar levels, and reduced lactate levels in
imal heart rate (fcmax), during a 90-min soccer match is close                   the second half of games compared with the first half (8). In
to the lactate threshold (LT), or 80 90% of fcmax (18).                         determining aerobic endurance, V     O2max is considered the
However, expressing intensity as an average over 90 min                          most important element. Other important determinants are
could result in a substantial loss of specific information.                      LT and running economy (gross oxygen cost of running per
Indeed, soccer matches have periods and situations of high-                      meter (CR)) (17). LT is the highest workload, oxygen con-
intensity activity where accumulation of lactate takes place.                    sumption or heart frequency in dynamic work using large
Therefore, the players need periods of low-intensity activity                    muscle groups, where production and elimination of lactate
to remove lactate from the working muscles.                                      balances (10). In endurance sports, LT might be a better
   A significant correlation between maximal oxygen uptake                                                                                O2max
  O2max) and distance covered during a match was found                           indicator of aerobic endurance performance than V
                                                                                 (9). LT might also change without changes in VO2max, and
(20,22). Moreover, the finding that the rank among the best
                                                                                 a higher LT means, theoretically, that a player could main-
four teams in the Hungarian top soccer division was the
                                          O2max (2) strength-                    tain a higher average intensity in an activity without accu-
same as the rank among their average V
                                O2max and performance. This                      mulation of lactate (10). Costill et al. (6) and Helgerud et al.
ens the correlation between V
                                                                                 (9), among others, have shown between-individual varia-
assumption is also supported by the results of Wislff et al.
(24), demonstrating a significant difference in V  O2max be-                     tions in CR. The causes of variability are not well under-
                                                                                 stood, but it seems likely that anatomical traits, mechanical/
                                                                                 neuromuscular skills, and storage of elastic energy are
0195-9131/01/3311-1925/$3.00/0                                                   important factors (17). Better CR among well-trained run-
MEDICINE & SCIENCE IN SPORTS & EXERCISE                                         ners compared with recreational runners are documented
Copyright  2001 by the American College of Sports Medicine                      (9,10). CR is normally expressed as oxygen consumption
Submitted for publication October 2000.                                          (V O2) at a standardized workload or V      O2 per meter when
Accepted for publication February 2001.                                          running (7,9). Hoff et al. (13) have shown that aerobic
TABLE 1. Physical and physiological characteristics of players ( SD).
                                              Height                                           [Hb]                                                     FEV1/VC
      N               Age (yr)                 (cm)                 Mass (kg)                (gdL1)                   Hct (%)     VC (L)                 (%)
      19             18.1 (0.8)             181.3 (5.6)             72.2 (11.1)             14.3 (1.1)             43.7 (1.6)    5.14 (0.88)           88.5 (3.2)
[Hb], hemoglobin concentration in blood; Hct, hematocrit; VC, vital capacity; FEV1, forced expiratory volume in 1 s.

performance can be increased by improving CR with a                                           organized purely as part of these playing sessions. No extra
strength training regimen, without affecting V    O2max or LT.                                strength training was performed. When the TG carried out
   Several studies describe the physiological, tactical, and                                  interval training, the CG performed extra technical training
technical parameters during a soccer match, which charac-                                     such as heading drills, practicing free kicks, and exercises
terize players at different levels (4,24). Cross-sectional stud-                              related to receiving the ball and changing direction.
ies show a correlation between V     O2max and these selected                                    Measurements. All players within a given team were
parameters (20,22); however, the basic question is whether                                    tested on the same day, and the tests were performed in the
this is a cause-and-effect phenomenon. Intervention studies                                   same order. When entering the laboratory, hemoglobin
concerning the effect of improving aerobic endurance on                                       (Hb), hematocrit (Hct), and lung function were measured for
soccer performance have not, to date, been reported.                                          normative data comparisons. For Hb and Hct determination,
   This study was carried out to evaluate the effects of a                                    blood was drawn from a fingertip and analyzed immediately
training protocol, aimed to improve aerobic endurance, on                                     using the Refletron (Boehringer Mannheim, Frankfurt, Ger-
soccer performance. The hypothesis was that increased aer-                                    many) and Ames microspin (Bayer Diagnostic, Munich,
obic endurance can improve distance covered, work inten-                                      Germany) devices, respectively. Vital capacity (VC) and
sity, number of sprints, and number of involvements with                                      forced expiratory volume in 1 s (FEV1) were determined
the ball during a soccer match.                                                               using a flow screen (Hoechberg, Germany). After these
                                                                                              preliminary tests, subjects completed a 20-min warm-up at
                                                                                              approximately 50  60% of V      O2max. Vertical jump height
                                                                                              was determined using a force platform with software specifi-
   Two Norwegian junior men elite teams, Nardo and                                            cally developed for the platform (BioWare, Kistler Instrumente
Strindheim, took part in the study. The subjects had been                                     AG, Winterthur, Switzerland). Jumping height was determined
playing soccer for more than 8 yr. Both teams had been                                        as the center of mass displacement calculated from force de-
among the most successful teams in Norway for the last 5 yr.                                  velopment and measured body mass. Strength testing consisted
Six of the players tested were members of the Norwegian                                       of one repetition maximum of bench press and of squats (90
national junior team. Players within each team were ran-                                      angle of the knee joints) repetition performed with a competi-
domly assigned into either a training group (TG, N  9) or                                     tion standard Olympic style bar and weights (T-100G, Eleiko
a control group (CG, N  10), so that each team had                                            Sport, Halmstad, Sweden).
members in both groups. In repeated determination of                                             A 40-m sprint test, a technical test, and a test of maximal
V O2max on the same subject, the standard deviation is 3%,                                    kicking velocity followed the strength tests. The time for the
including both biological and methodological variables (3).                                   first test was measured using photocells (Brower Timing
The actual number of subjects in the present study thus                                       Systems, South Draper, UT) at the start, at 10 m, and at
permitted detection of a 4.5% difference between groups (P                                    40 m. Each subject had two trials separated by 5 min of rest.
 0.05, power  0.90). Each subject reviewed and signed                                         When ready to sprint, the subjects decided themselves when
consent forms approved by the Human Research Review                                           to start the sprint test from a static position, with the time
Committee before the study. The subjects were only in-                                        being recorded when the subjects intercepted the photocell
formed how to perform the physical and physiological tests;                                   beam. The technical test was performed using 10 Select
no information was given about the video analysis during                                      senior balls with an air pressure of 0.8 bar. The balls were
the games. The head coaches spent equal time with their                                       placed 16 m from a goal, which was in turn divided into five
subjects in the TG and the CG. The athletes were truly unaware                                zones. If the ball was kicked into the 50-cm-wide center
of the tested hypothesis. The physical and physiological char-                                zone it was worth 3 points, 2 points if it was placed into an
acteristics of the subjects are presented in Table 1.                                         inner zone 25 cm each side of the center zone, and 1 point
   Training protocol. The aerobic training intervention                                       if placed into an outer zone reaching an additional 25 cm out
consisted of interval training, consisting of four times 4 min                                from the inner second zone. The subject was given 1 min to
each of running at an exercise intensity of 90 95% of fcmax                                  use his "preferential foot" to get the highest score possible.
for each player, separated by periods of 3 min jogging at                                     The technical test was repeated immediately after the
50  60% of fcmax. The interval training was administered as                                  V O2max test to verify fatiguing effect on technical skills.
an extension of the regular training, twice per week over an                                  Measurement of maximal kicking velocity was performed
8-wk period in the beginning of the season. A regular week                                    using a Panasonic (Tokyo, Japan) Wv-F350 E video camera
of training consisted of four times 1.5 h of practice and one                                 recorded at 50 Hz. The subject was free to decide the length
game. Technical, tactical, strength, and sprint training were                                 of the in-run. A centimeter scale was mounted on the wall
performed. About 1 h of each practice was organized as                                        parallel to the direction of the shot, giving the opportunity to
playing sessions in both teams. Endurance training was                                        calculate the speed of the ball as a fraction of the distance
1926       Official Journal of the American College of Sports Medicine                                                            
covered on the video picture. Each player was given two           on the basis of percent fcmax:  70%, 70  85%, 8590%,
trials. The best trial was used in the data handling.             90 95%, and  95%. Time spent in different intensity
   Following the strength, sprint, and technical tests, LT and    zones was calculated. Because of injuries, data were col-
V O2max were determined during treadmill running at 3            lected on eight subjects in both groups. All games were
inclination. The protocol used for measuring LT and               played on a high-quality indoor field consisting of artificial
V O2max has been described previously (10). Briefly, LT           curled nylon grass filled with sand. Video recordings were
determination began with a 10-min warm-up at 50  60% of          made using a single Panasonic M2 video camera 5 m from
V O2max, followed by measurement of baseline blood lactate        the sideline, 10 m higher than the field. A Videomedia
concentration ([la]b). LT was taken as the power output,          (Panasonic) VLC 32 editing table made slow motion and
V O2, or fc that gave a [la]b of 1.5 mmolL1 above                frame-by-frame analyses possible. A Wacom Digitizer SD-
baseline using 5-min work bouts during a continuous,              421-E digital board (Wacom Co., Ltd, Saitama, Japan) and
graded protocol. Subjects performed 5-min exercise stages         a marking pen, with specially designed software (Arntzen
progressing in intensity between 60 and 95% of V        O2max.    Engineering, Trondheim, Norway) for PC was used to fol-
Running speed was increased by 1 kmh at each stage,              low movements and to determine distances covered during
after a 20-s pause for blood sampling from a fingertip. The       the game. The following parameters were measured from
above-described protocol for LT was derived from a previ-         the video recordings:
ous study (10). Values for running speed, V  O2, fc, and [la]b
                                                                  Distance covered by a player.
were recorded during a series of running sessions. Each test
                                                                  Number of passes, defined as a trial to reach a team player
was performed at constant speed over a period of 20 min,
                                                                    with the ball.
and on separate days. The highest exercise intensity during
                                                                  Number of involvements with the ball, defined as all situ-
the constant speed tests, where the [la]b increased  1
                                                                    ations where the player is in physical contact with the ball
mmolL1 during the last 15 min, was then defined as LT.
                                                                    or in direct pressure on an opponent in possession of the
The values from the constant speed tests were then com-
pared with values from the graded tests. From the results of
                                                                  Number of sprints, sprinting for at least 2 s.
these studies, it was concluded that LT, using the graded
protocol, was reached at a V  O2 that gave on average [la]b          Similar parameters for soccer performance have been
1.5 mmolL        (ranging from 1.31.7 mmolL1) higher           used in earlier studies (4,25). Before the match analyses
than those found immediately after the warm-up period.            were carried out, a thorough reliability testing of the meth-
   After measuring LT, treadmill speed was increased to a         ods for video analyses was performed. The coefficient of
level that brought the subject to V  O2max and to exhaustion      reliability was 0.922 for the number of sprints, 0.970 for the
after about 3 min. CR was calculated at LT, the maximal           number of involvements with the ball, 0.998 for passes, and
exercise intensity at which it has been shown that a reliable     0.898 for distance covered during the match (unpublished
relationship exists between intensity and V O2 (9). The high-     results).
est fc during the last minute was taken as fcmax, measured by        Statistical analysis. All the results are reported as
short-range radio telemetry (Polar Sporttester, Polar Electro,    means  standard deviation (SD). An ANOVA analysis for
Finland). V O2, maximal minute ventilation (V   E), respiratory   repeated measurement was used to determine differences
exchange ratio (R), and breathing frequency were measured         among tests and between groups. Changes from pre- to
during each exercise stage using an Ergo Oxyscreen (Jaeger        posttraining in V O2max, LT, or CR given in percent is cal-
EOS sprint, Germany). Unhemolyzed blood lactate [la]b             culated on the basis of the unit mLkg0.75min1. Results
was determined using a YSI Model 1500 Sport Lactate               were accepted as significant at P  0.05. Group size and
Analyzer (Yellow Springs Instrument Co., Yellow Springs,          statistical power were estimated using nQuery Advisor soft-
OH).                                                              ware (Version 3.0, Statistical Solutions Ltd., Cork, Ireland).
   V O2max expressed as mLkg1min1 implies linearity
between oxygen uptake and body mass, which is not the
                              O2max as mLkg1min1, light         RESULTS
case (5). When expressing V
individuals are overestimated in terms of work capacity              During the training period, three subjects in the TG
(e.g., endurance athletes) and heavy individuals are under-       dropped out because of illness and injuries not related to the
estimated. The opposite is true when evaluating oxygen cost       training protocol. During the soccer matches, it was not
of running at submaximal workloads. Consequently, Wis-            possible to take heart frequency measurements from two
lff et al. (24), Helgerud (9), and Bergh et al. (5) have         subjects in the CG, and three subjects in the CG were unable
concluded that when comparisons among people of different         to play in the soccer matches. There were no differences
body mass are made for running, oxygen uptake should be           between the groups in terms of V     O2max before training,
expressed as mLkg0.75min1.                                      although the TG showed an increase in V    O2max of 10.8% (P
   Video analysis. Players were monitored by a video               0.05) after the training period (Table 2).
system during two regular games, played on a neutral field,          In the TG, LT and CR were improved by 16% (P  0.05)
before and after the training period. During games, fc was        and 6.7% (P  0.05), respectively. LT was not statistically
measured using a heart rate monitor (Polar Sporttester). The      changed expressed as percent V   O2max, but in terms of run-
fc measurements were divided into different intensity zones       ning speed at LT (Th) it increased from 11.1 kmh1 to 13.5
SOCCER PERFORMANCE                                                                Medicine & Science in Sports & Exercise   1927
TABLE 2. Results from physiological tests ( SD).
                                                                        TG (N  9)                                                            CG (N  10)
                                                      Pretraining                       Posttraining                        Pretraining                    Posttraining
           Lmin1                                      4.25 (1.9)                        4.59 (1.4)*                         4.06 (0.95)                     4.11 (0.99)
           mLkg1min1                                58.1 (4.5)                        64.3 (3.9)*                         58.4 (4.3)                      59.5 (4.4)
           mLkg0.75min1                            169.9 (9.6)                       188.3 (10.6)*                       169.2 (9.7)                     170.3 (9.8)
            Lmin1                                     3.5 (0.4)                         3.96 (0.3)*                         3.5 (0.4)                       3.46 (0.4)
            mLkg1min1                               47.8 (5.3)                        55.4 (4.1)*                         49.5 (3.3)                      50.0 (4.1)
            mLkg0.75min1                           139.9 (15.5)                      162.3 (12.2)*                       143.7 (15.2)                    143.2 (10.9)
            %V  O2max                                 82.4 (3.1)                        86.3 (2.1)                          86.2 (3.7)                      84.2 (2.8)
            % fcmax                                   87.4 (2.3)                        87.6 (2.4)                          89.2 (3.1)                      88.7 (4.2)
            LT (kmh1)                                11.1 (0.7)                        13.5 (0.4)*                         11.7 (0.4)                      11.5 (0.2)
         Running economy
           mLkg0.75m1                                0.75 (0.05)                        0.70 (0.04)*                        0.75 (0.04)                    0.74 (0.04)
           fcmax (beatsmin1)                        202 (5.5)                         203 (5.7)                            202 (6.3)                      202 (6.3)
           [la]b (mmolL1)                            8.1 (1.5)                          8.5 (1.9)                           7.8 (1.4)                      7.9 (1.5)
           R                                           1.17 (0.1)                         1.18 (0.1)                          1.18 (0.1)                     1.18 (0.1)
LT, running velocity at LT (3 inclination); [la]b (mmolL1), blood lactate concentration after V
                                                                                                  O2max testing; R, respiratory exchange ratio.
* P  0.05.

kmh1 (P  0.05). CR was constant within the range                                              DISCUSSION
60 95% V   O2max.
                                                                                                  The protocol used to improve the aerobic endurance in
   Results from video analyses during games are given in                                                               O2max by 10.8% in the TG. No sig-
                                                                                               this study increased V
Table 3. The TG increased the distance covered during a
                                                                                               nificant changes took place in the CG after the same period
game by 20% (P  0.01). The average increase in the                                                                             O2max from endurance train-
                                                                                               of time. This improvement in V
number of sprints per player during a match for the TG was
                                                                                               ing was in accordance with previous studies (21). Given the
100% (P  0.001), and the number of involvements with the                                                                                          O2max (3),
                                                                                               standard deviation in repeated determination of V
ball increased by 24.1% (P  0.05). The number of passes
                                                                                               the number of subjects studied permitted detection of a 4.5%
and the distribution between successful and not successful                                     difference between groups (P  0.05, power  0.90). The
passes did not change.                                                                         average V  O2max after training for the TG in the present
   Table 4 reflects the work intensity reported as average                                     study is above what is often reported for soccer players.
heart rate in percent of fcmax, during the first and the second                                Other studies have shown that the average V        O2max for
halves, as well as during the whole game. From before to                                       international level male soccer players ranges from 55 68
after training the TG increased the average percent of fcmax                                   mLkg1min1, with individual values higher than 70
in the game during the second half and during the whole                                        mLkg1min1 (18,24). These values are similar to those
game (P  0.05) (Table 4).                                                                      found in other team sports, but substantially lower than elite
   Figure 1 shows the time spent in the different intensity                                    performers in endurance sports, where values close to 90
zones (see Methods) in the first and second halves, before                                     mLkg1min1 have commonly been found. The fact that
and after training. Figure 1 also shows time spent at differ-                                  no changes occurred in the V   O2max of the control group is
ent intensities during the game after training. The TG had a                                   probably because of the lack of high-intensity endurance
significantly smaller decline in average percent of fcmax in                                   training during regular soccer practice.
the second half, at posttraining (P  0.05), and spent 19 min                                      The TG showed an improvement in LT in absolute terms
longer in the high-intensity zone ( 90% of fcmax) compared                                     but not relative to V O2max. In studies using the present LT
with the CG at the posttraining game (P  0.05). No                                             procedure, well-trained long-distance runners have LT at
changes were found in either group in the tests involving                                      about 85% V    O2max (9,10). This is in line with the present
speed, strength, jumping height, kicking velocity, and tech-                                   results for soccer players. Another LT protocol derived from
nical test (passing precision) (Table 5).                                                      fixed blood lactate values (e.g., 2 or 4 mmolL1) would

TABLE 3. Video analyses from soccer matches at pretest and posttest, as average numbers per player and match ( SD).
                                                                            TG (N  9)                                                         CG (N  10)
                                                          Pretraining                       Posttraining                       Pretraining                  Posttraining
        No. of sprints                                     6.2 (2.2)                        12.4 (4.3)**                        6.4 (2.4)                     7.5 (2.7)
        No. of involvements with ball                     47.4 (5.5)                        58.8 (6.9)*                        50.1 (6.1)                    52.4 (6.7)
        No. of passes                                     28.5 (3.5)                        30.7 (3.9)                         24.8 (3.1)                    26.9 (3.9)
          Successful passes                               19.4 (2.1)                        23.5 (2.7)                         16.6 (2.0)                    18.7 (2.3)
          Unsuccessful passes                              9.1 (1.9)                         7.2 (1.4)                          8.2 (1.7)                     8.2 (1.8)
        Distance covered (m)                            8619 (1237)                     10,335 (1608)**                      9076 (1512)                   9137 (1565)
* P  0.05; ** P  0.01.

1928       Official Journal of the American College of Sports Medicine                                                                   
TABLE 4. Average heart frequency during match (% fcmax) ( SD).                 pected on the basis of their more extensive running during
                                              Second                           practice compared with the CG. More running practice has
                           First Half          Half                 Total
                                                                               been shown to affect CR (9). A question remains, however,
    Pretraining                                                                whether or not the "soccer specific" work economy of the
      CG (N  8)            83.0 (3.0)        80.0 (2.0)          81.7 (3.3)
      TG (N  9)            84.0 (4.0)        81.2 (2.1)          82.7 (3.4)    players was improved. This means the oxygen cost of carrying
    Posttraining                                                               and trapping the ball, and starting, stopping, and changing
      CG (N  8)            84.2 (3.0)        81.1 (4.2)          82.6 (4.1)    direction. This was not addressed in this study. CR in the
      TG (N  9)            86.3 (3.2)        85.0 (3.0)*         85.6 (3.1)*   present study was higher than that reported earlier (9,10). The
* P  0.05.                                                                     reason for this is probably that these studies have used hori-
                                                                               zontal or 1 inclination treadmill during running, whereas the
give the same change in scores from before to after training,                  present study was carried out on 3 inclination. This gives
which was the focus of this study. The training protocol                       higher V  O2 at the same speed resulting in higher CR (lower
used in this study was not specifically designed to improve                    economy). The CR was constant within the running velocities
LT. Such a training regimen would normally imply the                           just below and higher than LT, and this is consistent with data
utilization of work intensity of between 85 and 90% of fcmax                   obtained by Di Prampero et al. (7) and Helgerud (9).
(17). Improvements in V    O2max are, however, normally fol-                      In this study, the work intensity during soccer matches
lowed by improved LT. The improvement in LT is therefore                       was studied through an analysis of fc during matches. At
a result of the change in V  O2max and CR. The TG spent 19                     pretraining, there were no differences between the TG and
min more than the CG in the high-intensity zone ( 90% of                       the CG. However, the TG improved their average intensity
fcmax). This is probably because of increased V   O2max in the                 at posttraining. In practical terms, as the results presented in
TG, since the fractional utilization of VO2max has been                        Table 3 show, this means that a player from the CG, having
shown to be partly dependent on the state of training (9).                     a fcmax of 200 beatsmin1, at posttraining would have an
The ability to perform for longer periods of time at the same                  average fc of 165 beatsmin1, whereas a player from the
relative exercise intensity is, however, more a function of                    TG, with the same fcmax, would have an average intensity of
efficiency in usage of glycogen. Thus, the amount of gly-                      171 beatsmin1. The time spent in the different intensity
cogen and the training status of the muscles involved in the                   zones in this experiment correspond with the findings from
exercise are decisive for the maintenance of a specific relative               Rhode and Espersen (19). Improved work intensity as a
work intensity. Endurance training in soccer, more than a                      result of the intervention seems logical, as the average distance
training regimen aimed to improve LT only, should thus em-                     covered during a game for the TG increased by 1716 m and the
phasize improvement in V    O2max and, in turn, improve LT.                    average number of sprints per player increased from 6 to 12.
   CR was also improved by 6.7% in the TG as a result of the                   These results support the findings from Smaros (20) showing
training protocol. Improved CR would, however, be ex-                          that the players with the highest V    O2max had the highest

                                                                                             FIGURE 1--Upper panels show time spent in the dif-
                                                                                             ferent intensity zones in first and second halves before
                                                                                             training. Intensities are expressed in relation to max-
                                                                                             imal heart rate. Middle panels show the corresponding
                                                                                             values after training. Lower panel shows time spent at
                                                                                             different intensities during the game after training.
                                                                                             Values are mean  SD. Significantly different from
                                                                                             training group, *P < 0.05; **P < 0.01; ***P < 0.001.

SOCCER PERFORMANCE                                                                              Medicine & Science in Sports & Exercise       1929
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    BC BASEBALL UMPIRES ASSOCIATION LEVEL 3 EXAM 2013 READ THE INSTRUCTIONS BEFORE PROCEEDING! Many times during a game we deal with plays that involve more than one rule or interpretation. In this exam the 1st 20 questions will be True/False and for the remainder you …

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