Downloaded from http://bjsm.bmj.com/ on February 1, 2015 - Published by group.bmj.com
Original article
Effect of plyometric training on sand versus grass on
muscle soreness and jumping and sprinting ability in
soccer players
F M Impellizzeri,1 E Rampinini,1 C Castagna,2 F Martino,3 S Fiorini,3 U Wisloff4,5
ABSTRACT concentric muscular contractions potentiated by
1
Human Performance Objective: The lower impact on the musculoskeletal the stretch reflex.6 The rapid eccentric muscle
Laboratory, Mapei Sport system induced by plyometric exercise on sand compared actions induce muscle damage and, consequently,
Research Center, Castellanza, to a firm surface might be useful to reduce the stress of muscular soreness and a transient decrease in
Varese, Italy; 2 School of Sport
and Exercise Sciences, Faculty intensified training periods or during rehabilitation from strength.10 11 Plyometric training is commonly
of Medicine and Surgery, injury. The aim of this study was to compare the effects performed on firm surfaces (eg grass and wood),
University of Rome Tor Vergata, of plyometric training on sand versus a grass surface on but a more recent study has shown that drop
Rome, Italy; 3 Facoltà di muscle soreness, vertical jump height and sprinting ability. jumps on sand induce less muscle damage when
Medicina e Chirurgia, Corso di compared to a firm surface.12 Indeed, Miyama and
Laurea Specialistica in Scienze e Design: Parallel two-group, randomised, longitudinal
Tecnica dello Sport, Università (pretest2post-test) study. Nosaka12 found a greater reduction in maximal
degli Studi di Firenze, Firenze, Methods: After random allocation, 18 soccer players isometric force following 100 consecutive drop
Italia; 4 Department of completed 4 weeks of plyometric training on grass (grass jumps on a firm compared to sand surface, while
Circulation and Medical Imaging, muscle soreness and creatine kinase concentration
Norwegian University of Science group) and 19 players on sand (sand group). Before and
and Technology, Faculty of after plyometric training, 10 m and 20 m sprint time, were lower on sand. However, jumping on sand
Medicine, Trondheim, Norway; squat jump (SJ), countermovement jump (CMJ), and causes a lower reuse of elastic energy and energy
5
Department of Cardiology, St. eccentric utilization ratio (CMJ/SJ) were determined. loss due to feet slipping during the concentric
Olav’s Hospital, Trondheim, action.12 13 This might induce different training
Norway
Muscle soreness was measured using a Likert scale.
Results: No training surface 6 time interactions were effects compared to training on a firm surface. On
Correspondence to: found for sprint time (p.0.87), whereas a trend was the other hand, the lower stress on the muscu-
Franco M Impellizzeri, found for SJ (p = 0.08), with both groups showing similar loskeletal system may decrease the risk of injuries
Neuromuscular Research and the overall physical strain of training ses-
Laboratory, Schulthess Clinic, improvements (p,0.001). On the other hand, the grass
Lengghalde 2, 8008 Zurich, group improved their CMJ (p = 0.033) and CMJ/SJ sions.14 This may be particularly helpful during the
Switzerland; franco. (p = 0.005) significantly (p,0.001) more than players in preseason training period where a high incidence of
the sand group. In contrast, players in the sand group overuse injuries has frequently been reported in
experienced less muscle soreness than those in the grass soccer players.15 16 This could be a consequence of
Accepted 14 May 2007 factors such as hard surface17 18 and the high
Published Online First group (p,0.001).
training load.19 Furthermore, the lower impact on
25 May 2007 Conclusions: Plyometric training on sand improved both
the musculoskeletal system induced by plyometric
jumping and sprinting ability and induced less muscle
training on sand might be useful during rehabilita-
soreness. A grass surface seems to be superior in
tion programmes. According to Mihama and
enhancing CMJ performance while the sand surface
Nosaka,12 less muscle soreness and muscle damage
showed a greater improvement in SJ. Therefore,
does not necessarily imply that plyometric training
plyometric training on different surfaces may be
on sand is preferable to that on grass. Indeed,
associated with different training-induced effects on some
possible differences in the training effects induced
neuromuscular factors related to the efficiency of the
by sand or firm surfaces should be taken into
stretch-shortening cycle.
account. However, to the best of our knowledge,
no studies have examined the effect of plyometric
training completed on different surfaces.
Soccer is a high-intensity, intermittent activity
Therefore, the aim of this study was to compare
during which players are required to repeatedly
the effects of plyometric training on muscle
perform striding, turning, sprinting and jumping,
soreness, vertical jump height and sprinting ability
which place considerable demands on the neuro-
when performed on either a sand or grass surface.
muscular system.1 2 Therefore, the ability of the
lower limb muscles to produce power is an
important fitness component for soccer players.3 METHODS
Plyometric training has been shown to be an Study design and randomisation
effective method for the improvement of both A parallel two-group, randomised, longitudinal
sprinting and jumping ability4–6 and it has also been (pretest2post-test) design was used. After baseline
reported to improve running economy,7 joint measurements, subjects were randomly allocated
stability and reduce the severity of knee injuries.8 9 to two intervention groups: plyometric training on
For these reasons, soccer training commonly sand (sand group) and plyometric training on grass
includes this form of muscular power training. (grass group). Balanced restricted randomization
Plyometric training typically consists of stretch- was obtained using blocks (block sizes of 4 and 6)
shortening cycle exercises characterized by multi- with allocation ratio of one-to-one.20 As the
joint actions, rapid eccentric phases and explosive independent variable was training surface, no
42 Br J Sports Med 2008;42:42–46. doi:10.1136/bjsm.2007.038497
, Downloaded from http://bjsm.bmj.com/ on February 1, 2015 - Published by group.bmj.com
Original article
control group was used. Baseline measurements were completed avoid an influence of the upper limbs on jump performance.
1 week before the commencement of the training period, while Players performed the SJ starting from a standing position,
postintervention measurements were carried out 4 weeks after bending the knees to 90u, stopping for 3 s, and then jumping as
the end of the experimental training period. This tapering high as possible trying to avoid any knee or trunk counter-
duration (4 weeks) was necessary and corresponded to the movement. CMJs were performed starting from a standing
recovery period needed to maximize and highlight the training- position after which players were asked to jump as high as
induced changes after 4 weeks of high-intensity plyometric possible with a rapid, preparatory downward eccentric action.
training.21 Furthermore, in the current study we adopted the Jump height was estimated from flight time calculated as the
training programme used by Luebbers et al.21 to ensure time between take-off and subsequent landing.22 The eccentric
improvement in jumping ability, with the slight modification utilization ratio was calculated as CMJ/SJ.23 The best result for
that set 6 repetitions instead of set 6 distance was used. each jump type was used for the analysis.
Participants Sprinting tests
Forty-four amateur soccer players (mean (SD) body mass 74 kg The 10 m and 20 m sprint tests were performed 30 min after
(7), height 178 cm (7) and age 25 years (4)) were involved in the the jump test session and following a further warm-up
study. Written informed consent was obtained after verbal and consisting of low-intensity running and striding. Two trials of
written explanation of the experimental procedures. The study each test, with a full recovery between sprints, were completed.
was approved by an independent institutional review board Sprint time was recorded with two telemetric photocells
according to the guidelines and recommendations for European (Microgate, Bolzano, Italy) placed at the start and at the finish
ethics committees. All subjects were familiarized with all lines of the two sprint distances. The best sprint time for each
testing procedures prior to the commencement of the study distance was used for the analysis.
and had already had experience of plyometric training.
Muscle soreness
Plyometric training programme Muscle soreness was assessed each day of the training period
As the preseason training period lasted 4 weeks, we employed a and before the post-test testing session using an Italian version
4-week plyometric training programme similar to that used by of the 7-point Likert scale of muscle soreness24(table 2). A mean
Luebbers et al.21 that has been shown to be effective in value for the training period for each training group was
enhancing lower limb muscular anaerobic power (table 1). calculated.
Training was completed on a grass pitch or on a 0.2 m-deep dry
sand surface. The characteristics of the sand (ie grain diameter) Statistical analysis
resulted in a harder sand surface compared to beach sand. The Data are presented as mean (SD). We tested the null hypothesis
plyometric training sessions were completed 3 times a week in of no difference between groups in all baseline measures using
addition to the usual training consisting of generic and specific multiple unpaired Student t tests. A two-way mixed analysis of
aerobic interval training and technical-tactical training. variance (ANOVA) was used on each continuous dependent
Participants were asked to exert a maximal intensity during variable. The independent variables included one between
all the training sessions. Recovery time between repetitions and subjects factor, plyometric training surface, with two levels
sets were 15–30 s and 1–2 min, respectively. During the 4-week (grass and sand), and one within subject factor, time, with two
recovery period corresponding to the start of the competitive levels (pretest and post-test). We used these ANOVAs to test
season, soccer players trained three times a week and competed the null hypothesis of no different change over time between
once a week in an official match, but no plyometric exercises or the grass and the sand group (plyometric training surface 6time
sprint training were completed. interaction) and no different change over time in response to
plyometric training intervention. When a significant F value
Training outcomes was found, Bonferroni’s post hoc test was applied. Effect sizes
(g2) were also calculated, and values of 0.01, 0.06 and above 0.15
Jump tests
were considered small, medium and large, respectively.25 The
Soccer players completed the jump test sessions after a 15 min
level of statistical significance was set at p,0.05.
warm-up consisting of low-intensity running, striding and self-
administered submaximal jumps performed as practice and
specific additional warm-up. All jumps were performed on a RESULTS
photocell mat (Optojump, Microgate, Bolzano, Italy) in a Thirty-seven players completed the study. No differences were
random order with at least five trials of each type of jump test: found between groups in baseline values. No significant
squat jump (SJ) and countermovement jump (CMJ). All vertical interactions were found for the 10 m sprint time and 20 m
jumps were completed keeping the hands on the iliac crest to sprint time, while significant interactions were found for CMJ
Table 1 Four-week plyometric training programme* modified from Table 2 Likert scale of muscle soreness from Vickers24
Luebbers et al21 Value Description
Number of sets (number of repetitions)
0 A complete absence of soreness
Exercise Week 1 Week 2 Week 3 Week 4 1 A light pain felt only when touched/a vague ache
Vertical jumping 15 (10) 20 (10) 25 (10) 25 (10) 2 A moderate pain felt only when touched/a slight persistent pain
Bounding 3 (10) 4 (10) 5 (10) 5 (10) 3 A light pain when walking up or down stairs
Broad jumping 5 (8) 5 (10) 7 (10) 8 (10) 4 A light pain when walking on a flat surface/painful
Drop jump 3 (5) 5 (9) 6 (15) 6 (15) 5 A moderate pain, stiffness or weakness when walking/very painful
6 A severe pain that limits my ability to move
*See text for details.
Br J Sports Med 2008;42:42–46. doi:10.1136/bjsm.2007.038497 43
Original article
Effect of plyometric training on sand versus grass on
muscle soreness and jumping and sprinting ability in
soccer players
F M Impellizzeri,1 E Rampinini,1 C Castagna,2 F Martino,3 S Fiorini,3 U Wisloff4,5
ABSTRACT concentric muscular contractions potentiated by
1
Human Performance Objective: The lower impact on the musculoskeletal the stretch reflex.6 The rapid eccentric muscle
Laboratory, Mapei Sport system induced by plyometric exercise on sand compared actions induce muscle damage and, consequently,
Research Center, Castellanza, to a firm surface might be useful to reduce the stress of muscular soreness and a transient decrease in
Varese, Italy; 2 School of Sport
and Exercise Sciences, Faculty intensified training periods or during rehabilitation from strength.10 11 Plyometric training is commonly
of Medicine and Surgery, injury. The aim of this study was to compare the effects performed on firm surfaces (eg grass and wood),
University of Rome Tor Vergata, of plyometric training on sand versus a grass surface on but a more recent study has shown that drop
Rome, Italy; 3 Facoltà di muscle soreness, vertical jump height and sprinting ability. jumps on sand induce less muscle damage when
Medicina e Chirurgia, Corso di compared to a firm surface.12 Indeed, Miyama and
Laurea Specialistica in Scienze e Design: Parallel two-group, randomised, longitudinal
Tecnica dello Sport, Università (pretest2post-test) study. Nosaka12 found a greater reduction in maximal
degli Studi di Firenze, Firenze, Methods: After random allocation, 18 soccer players isometric force following 100 consecutive drop
Italia; 4 Department of completed 4 weeks of plyometric training on grass (grass jumps on a firm compared to sand surface, while
Circulation and Medical Imaging, muscle soreness and creatine kinase concentration
Norwegian University of Science group) and 19 players on sand (sand group). Before and
and Technology, Faculty of after plyometric training, 10 m and 20 m sprint time, were lower on sand. However, jumping on sand
Medicine, Trondheim, Norway; squat jump (SJ), countermovement jump (CMJ), and causes a lower reuse of elastic energy and energy
5
Department of Cardiology, St. eccentric utilization ratio (CMJ/SJ) were determined. loss due to feet slipping during the concentric
Olav’s Hospital, Trondheim, action.12 13 This might induce different training
Norway
Muscle soreness was measured using a Likert scale.
Results: No training surface 6 time interactions were effects compared to training on a firm surface. On
Correspondence to: found for sprint time (p.0.87), whereas a trend was the other hand, the lower stress on the muscu-
Franco M Impellizzeri, found for SJ (p = 0.08), with both groups showing similar loskeletal system may decrease the risk of injuries
Neuromuscular Research and the overall physical strain of training ses-
Laboratory, Schulthess Clinic, improvements (p,0.001). On the other hand, the grass
Lengghalde 2, 8008 Zurich, group improved their CMJ (p = 0.033) and CMJ/SJ sions.14 This may be particularly helpful during the
Switzerland; franco. (p = 0.005) significantly (p,0.001) more than players in preseason training period where a high incidence of
the sand group. In contrast, players in the sand group overuse injuries has frequently been reported in
experienced less muscle soreness than those in the grass soccer players.15 16 This could be a consequence of
Accepted 14 May 2007 factors such as hard surface17 18 and the high
Published Online First group (p,0.001).
training load.19 Furthermore, the lower impact on
25 May 2007 Conclusions: Plyometric training on sand improved both
the musculoskeletal system induced by plyometric
jumping and sprinting ability and induced less muscle
training on sand might be useful during rehabilita-
soreness. A grass surface seems to be superior in
tion programmes. According to Mihama and
enhancing CMJ performance while the sand surface
Nosaka,12 less muscle soreness and muscle damage
showed a greater improvement in SJ. Therefore,
does not necessarily imply that plyometric training
plyometric training on different surfaces may be
on sand is preferable to that on grass. Indeed,
associated with different training-induced effects on some
possible differences in the training effects induced
neuromuscular factors related to the efficiency of the
by sand or firm surfaces should be taken into
stretch-shortening cycle.
account. However, to the best of our knowledge,
no studies have examined the effect of plyometric
training completed on different surfaces.
Soccer is a high-intensity, intermittent activity
Therefore, the aim of this study was to compare
during which players are required to repeatedly
the effects of plyometric training on muscle
perform striding, turning, sprinting and jumping,
soreness, vertical jump height and sprinting ability
which place considerable demands on the neuro-
when performed on either a sand or grass surface.
muscular system.1 2 Therefore, the ability of the
lower limb muscles to produce power is an
important fitness component for soccer players.3 METHODS
Plyometric training has been shown to be an Study design and randomisation
effective method for the improvement of both A parallel two-group, randomised, longitudinal
sprinting and jumping ability4–6 and it has also been (pretest2post-test) design was used. After baseline
reported to improve running economy,7 joint measurements, subjects were randomly allocated
stability and reduce the severity of knee injuries.8 9 to two intervention groups: plyometric training on
For these reasons, soccer training commonly sand (sand group) and plyometric training on grass
includes this form of muscular power training. (grass group). Balanced restricted randomization
Plyometric training typically consists of stretch- was obtained using blocks (block sizes of 4 and 6)
shortening cycle exercises characterized by multi- with allocation ratio of one-to-one.20 As the
joint actions, rapid eccentric phases and explosive independent variable was training surface, no
42 Br J Sports Med 2008;42:42–46. doi:10.1136/bjsm.2007.038497
, Downloaded from http://bjsm.bmj.com/ on February 1, 2015 - Published by group.bmj.com
Original article
control group was used. Baseline measurements were completed avoid an influence of the upper limbs on jump performance.
1 week before the commencement of the training period, while Players performed the SJ starting from a standing position,
postintervention measurements were carried out 4 weeks after bending the knees to 90u, stopping for 3 s, and then jumping as
the end of the experimental training period. This tapering high as possible trying to avoid any knee or trunk counter-
duration (4 weeks) was necessary and corresponded to the movement. CMJs were performed starting from a standing
recovery period needed to maximize and highlight the training- position after which players were asked to jump as high as
induced changes after 4 weeks of high-intensity plyometric possible with a rapid, preparatory downward eccentric action.
training.21 Furthermore, in the current study we adopted the Jump height was estimated from flight time calculated as the
training programme used by Luebbers et al.21 to ensure time between take-off and subsequent landing.22 The eccentric
improvement in jumping ability, with the slight modification utilization ratio was calculated as CMJ/SJ.23 The best result for
that set 6 repetitions instead of set 6 distance was used. each jump type was used for the analysis.
Participants Sprinting tests
Forty-four amateur soccer players (mean (SD) body mass 74 kg The 10 m and 20 m sprint tests were performed 30 min after
(7), height 178 cm (7) and age 25 years (4)) were involved in the the jump test session and following a further warm-up
study. Written informed consent was obtained after verbal and consisting of low-intensity running and striding. Two trials of
written explanation of the experimental procedures. The study each test, with a full recovery between sprints, were completed.
was approved by an independent institutional review board Sprint time was recorded with two telemetric photocells
according to the guidelines and recommendations for European (Microgate, Bolzano, Italy) placed at the start and at the finish
ethics committees. All subjects were familiarized with all lines of the two sprint distances. The best sprint time for each
testing procedures prior to the commencement of the study distance was used for the analysis.
and had already had experience of plyometric training.
Muscle soreness
Plyometric training programme Muscle soreness was assessed each day of the training period
As the preseason training period lasted 4 weeks, we employed a and before the post-test testing session using an Italian version
4-week plyometric training programme similar to that used by of the 7-point Likert scale of muscle soreness24(table 2). A mean
Luebbers et al.21 that has been shown to be effective in value for the training period for each training group was
enhancing lower limb muscular anaerobic power (table 1). calculated.
Training was completed on a grass pitch or on a 0.2 m-deep dry
sand surface. The characteristics of the sand (ie grain diameter) Statistical analysis
resulted in a harder sand surface compared to beach sand. The Data are presented as mean (SD). We tested the null hypothesis
plyometric training sessions were completed 3 times a week in of no difference between groups in all baseline measures using
addition to the usual training consisting of generic and specific multiple unpaired Student t tests. A two-way mixed analysis of
aerobic interval training and technical-tactical training. variance (ANOVA) was used on each continuous dependent
Participants were asked to exert a maximal intensity during variable. The independent variables included one between
all the training sessions. Recovery time between repetitions and subjects factor, plyometric training surface, with two levels
sets were 15–30 s and 1–2 min, respectively. During the 4-week (grass and sand), and one within subject factor, time, with two
recovery period corresponding to the start of the competitive levels (pretest and post-test). We used these ANOVAs to test
season, soccer players trained three times a week and competed the null hypothesis of no different change over time between
once a week in an official match, but no plyometric exercises or the grass and the sand group (plyometric training surface 6time
sprint training were completed. interaction) and no different change over time in response to
plyometric training intervention. When a significant F value
Training outcomes was found, Bonferroni’s post hoc test was applied. Effect sizes
(g2) were also calculated, and values of 0.01, 0.06 and above 0.15
Jump tests
were considered small, medium and large, respectively.25 The
Soccer players completed the jump test sessions after a 15 min
level of statistical significance was set at p,0.05.
warm-up consisting of low-intensity running, striding and self-
administered submaximal jumps performed as practice and
specific additional warm-up. All jumps were performed on a RESULTS
photocell mat (Optojump, Microgate, Bolzano, Italy) in a Thirty-seven players completed the study. No differences were
random order with at least five trials of each type of jump test: found between groups in baseline values. No significant
squat jump (SJ) and countermovement jump (CMJ). All vertical interactions were found for the 10 m sprint time and 20 m
jumps were completed keeping the hands on the iliac crest to sprint time, while significant interactions were found for CMJ
Table 1 Four-week plyometric training programme* modified from Table 2 Likert scale of muscle soreness from Vickers24
Luebbers et al21 Value Description
Number of sets (number of repetitions)
0 A complete absence of soreness
Exercise Week 1 Week 2 Week 3 Week 4 1 A light pain felt only when touched/a vague ache
Vertical jumping 15 (10) 20 (10) 25 (10) 25 (10) 2 A moderate pain felt only when touched/a slight persistent pain
Bounding 3 (10) 4 (10) 5 (10) 5 (10) 3 A light pain when walking up or down stairs
Broad jumping 5 (8) 5 (10) 7 (10) 8 (10) 4 A light pain when walking on a flat surface/painful
Drop jump 3 (5) 5 (9) 6 (15) 6 (15) 5 A moderate pain, stiffness or weakness when walking/very painful
6 A severe pain that limits my ability to move
*See text for details.
Br J Sports Med 2008;42:42–46. doi:10.1136/bjsm.2007.038497 43
