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Olsen OE, Myklebust G, Engebretsen L, Holme I, Bahr R. Exercises to prevent lower limb injuries in youth sports: cluster randomised controlled trial. BMJ.330:449

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To investigate the effect of a structured warm-up programme designed to reduce the incidence of knee and ankle injuries in young people participating in sports. Cluster randomised controlled trial with clubs as the unit of randomisation. 120 team handball clubs from central and eastern Norway (61 clubs in the intervention group, 59 in the control group) followed for one league season (eight months). 1837 players aged 15-17 years; 958 players (808 female and 150 male) in the intervention group; 879 players (778 female and 101 male) in the control group. A structured warm-up programme to improve running, cutting, and landing technique as well as neuromuscular control, balance, and strength. The rate of acute injuries to the knee or ankle. During the season, 129 acute knee or ankle injuries occurred, 81 injuries in the control group (0.9 (SE 0.09) injuries per 1000 player hours; 0.3 (SE 0.17) in training v 5.3 (SE 0.06) during matches) and 48 injuries in the intervention group (0.5 (SE 0.11) injuries per 1000 player hours; 0.2 (SE 0.18) in training v 2.5 (SE 0.06) during matches). Fewer injured players were in the intervention group than in the control group (46 (4.8%) v (76 (8.6%); relative risk intervention group v control group 0.53, 95% confidence interval 0.35 to 0.81). A structured programme of warm-up exercises can prevent knee and ankle injuries in young people playing sports. Preventive training should therefore be introduced as an integral part of youth sports programmes.
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doi:10.1136/bmj.38330.632801.8F
2005;330;449-; originally published online 7 Feb 2005; BMJ
Roald Bahr
Odd-Egil Olsen, Grethe Myklebust, Lars Engebretsen, Ingar Holme and
trial
youth sports: cluster randomised controlled
Exercises to prevent lower limb injuries in
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Papers
Exercises to prevent lower limb injuries in youth sports: cluster
randomised controlled trial
Odd-Egil Olsen, Grethe Myklebust, Lars Engebretsen, Ingar Holme, Roald Bahr
Abstract
Objective To investigate the effect of a structured warm-up
programme designed to reduce the incidence of knee and
ankle injuries in young people participating in sports.
Design Cluster randomised controlled trial with clubs as the
unit of randomisation.
Setting 120 team handball clubs from central and eastern
Norway (61 clubs in the intervention group, 59 in the control
group) followed for one league season (eight months).
Participants 1837 players aged 15-17 years; 958 players (808
female and 150 male) in the intervention group; 879 players
(778 female and 101 male) in the control group.
Intervention A structured warm-up programme to improve
running, cutting, and landing technique as well as
neuromuscular control, balance, and strength.
Main outcome measure The rate of acute injuries to the knee
or ankle.
Results During the season, 129 acute knee or ankle injuries
occurred, 81 injuries in the control group (0.9 (SE 0.09) injuries
per 1000 player hour s; 0.3 (SE 0.17) in training v 5.3 (SE 0.06)
during matches) and 48 injuries in the intervention group (0.5
(SE 0.11) injuries per 1000 player hours; 0.2 (SE 0.18) in
training v 2.5 (SE 0.06) during matches). Fewer injured players
were in the intervention group than in the control group (46
(4.8%) v (76 (8.6%); relative risk intervention group v control
group 0.53, 95% confidence interval 0.35 to 0.81).
Conclusion A structured programme of warm-up exercises can
prevent knee and ankle injuries in young people playing sports.
Preventive training should therefore be introduced as an
integral part of youth sports programmes.
Introduction
Regular physical activity reduces the risk of premature mortality
in general and of coronary heart disease, hypertension, colon
cancer, obesity, and diabetes mellitus in particular.
12
However,
participation in sports also entails a risk of injury for all athletes,
from the elite to the recreational level. Studies from Scandinavia
document that sports injuries constitute 10-19% of all acute
injuries seen in emergency departments, and the most common
types are knee and ankle injuries.
3
Serious knee injuries, such as
injuries to the anterior cruciate ligament, are a growing cause of
concern. The highest incidence is seen in adolescents playing
pivoting sports such as football, basketball, and team handball. In
these sports, women are three to five times more likely to
contract a serious knee injury than men.
4–6
Injuries to the anterior cruciate ligament may require
surgery, always entail a long rehabilitation period, and drastically
increase the risk of long term sequelae.
7
Although treatment
methods have advanced notably, there is no evidence to show
that repair of a ruptured anterior cruciate ligament or isolated
cartilage lesions prevents early development of osteoarthritis.
7
Effective methods for preventing injuries therefore need to be
developed.
Some studies report promising results, indicating that it may
be possible to reduce the incidence of knee and ankle injuries
among adults
8–10
and adolescents.
11–14
However, these studies are
small and mainly non-randomised, with important methodo-
logical limitations. Prospective randomised intervention studies
are therefore needed, especially among children and adoles-
cents, to assess the efficacy of interventions aiming to reduce
injuries.
We conducted a randomised controlled trial to investigate
the effect of a structured programme of warm-up exercises used
to prevent acute injuries of the lower limb in young people play-
ing sports. To minimise overlap within clubs, we used a cluster
design.
Methods
One hundred and twenty three clubs agreed to participate in the
study, and we block randomised these, with four clubs in each
block to an intervention or control group. To reduce potential
confounding, we matched the clubs by region, playing level, and
sex and number of players. The statistician (IH) who conducted
the randomisation was not involved in the intervention. Box 1
gives details of the procedure used to recruit clubs.
We informed clubs allocated to the intervention group that
they would receive a programme of warm-up exercises used to
prevent injuries. We asked the clubs in the control group to do
their training as usual during the season and informed them that
they would receive the same programme as the intervention
group at the start of the subsequent season.
Box 1: Recruiting clubs to the study
All 145 clubs in the 16 year and 17 year divisions from central
and eastern Norway, organised by the Norwegian Handball
Federation, received an invitation to participate in the study
during one eight month season (September 2002 to April 2003)
The clubs practised one to five times per week and played
between 20 and 50 matches during the season, depending on
their ability and ambition
The clubs were recruited from June to August 2002 through
the website of the Norwegian Handball Federation, and a letter
with information about the purpose and the design of the study
went to the coaches, who also infor med the players
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Intervention
The warm-up programme was developed by medical staff from
the Oslo Sports Trauma Research Center and coaching staff
from the Norwegian Handball Federation, and its feasibility had
been tested in four clubs during the previous season. The
programme included four different sets of exercises, each of
increasing difficulty.
At the start of the league season (September), the clubs in the
intervention group received one visit from an instructor from
the handball federation. In addition, instructors followed up the
clubs with a visit midway through the season (January). The
instructors had been familiarised with the programme during a
two hour seminar, in which they received theoretical and practi-
cal training on how to conduct the programme. The clubs
received an exercise book, five wobble boards (disc diameter 38
cm; Norpro, Notodden, Norway, 2000) and five balance mats
(40×50 cm
2
, 7 cm thick; Alusuisse Airex, Sins, Switzerland, 2000).
The coaches were asked to use the programme at the beginning
of every training session for 15 consecutive sessions and then
once a week during the remainder of the season.
The main focus of the exercises was to improve awareness
and control of knees and ankles during standing, running,
cutting, jumping, and landing. The programme consisted of
exercises with the ball, including the use of the wobble board and
balance mat (box 2, fig 1, and fig 2), for warm up, technique, bal-
ance, and strength.
The players were encouraged to be focused and conscious of
the quality of their movements, with emphasis given to core sta-
bility and position of the hip and knee in relation to the foot (the
“knee over toe” position). They were also asked to watch each
other closely and give each other feedback during the training.
They were instructed to spend 4-5 minutes on each exercise
group for a total duration of 15-20 minutes.
Data on injury and exposure were reported by the
physiotherapists using a web based database in which all the data
were coded anonymously. At the end of the season, the recorded
data were confirmed, or if necessary corrected, by the coaches.
Box 3 shows the definitions we used in registering injuries.
Outcome measures
We defined the primary outcome as an acute injury to the knee
or ankle. A secondary outcome was defined as any injury to the
lower limbs. We also included secondary analyses of injuries
overall (including all injuries) and injuries to the upper limb. We
included all injuries reported after an intervention club had
completed the first session of the training aiming to prevent
injuries (and from the same date in the control clubs randomised
in the same block), to compare the number of injured players
and incidence of injury between the intervention group and the
control group.
The number of injured players was based on data from indi-
vidual players and the incidence of injuries on summary data of
injuries and exposures for the whole group. Data on players who
dropped out during the study period were included for the
entire period of their participation.
Ten research physiotherapists who were blinded to group
allocation recorded injuries in both groups, using definitions
(box 3) and a standardised injury questionnaire described in our
earlier study (Olsen OE, Myklebust G, Engebretsen L, Bahr R.
Injury pattern in youth team handball: a comparison of two pro-
spective registration methods. Submitted for publication to Scand
J Med Sci Sports).
The physiotherapists were in contact with the coaches at least
every month to record injured players and exposure data. They
interviewed injured players, either in person or by telephone,
and in most cases within four weeks (range one day to four
months). They were responsible for roughly the same number of
clubs from each of the groups (11 to 13 clubs each).
The coaches of the clubs receiving the intervention recorded
compliance on a designated form as the number of injury
prevention sessions, the duration of each session in minutes, and
the average attendance of the players (in per cent). At the end of
the season we also obtained information on prevention training
conducted by the control clubs, including the types and volume
of exercises used.
Sample size
In youth team handball, the incidence of acute injuries to the
knee and ankle is estimated to be 12 per 100 players per league
season.
11 15
From a pilot study conducted to determine the
incidence of injury during the previous season (submitted for
publication), we estimated that the cluster effects for club
randomisation gave an inflation factor of 2.0 based on a cluster
size of 15 and an intracluster correlation coefficient of 0.07. We
then calculated that to achieve 90% power with = 5% to detect
a relative risk reduction of 50%, we would need 915 players in
each group. Therefore, when we initiated the trial, we were hop-
ing to include 60 clubs in each group (a total of 120 clubs; with
an average of 15 players in each club).
Statistical methods
We used Stata, version 8.0 (Stata Corporation, Lakeway Drive,
Texas, 2003), for the statistical analysis. We undertook all statisti-
cal analyses according to a prespecified plan. We used the
Box 2: Programme of warm-up exercises used to prevent
injuries
Warm-up exercises
(30 seconds and one repetition each)
Jogging end to end
Backward running with sidesteps
Forward running with knee lifts and heel kicks
Sideways running with crossovers (“carioca”)
Sideways running with arms lifted (“parade”)
Forward running with trunk rotations
Forward running with intermittent stops
Speed run
Technique
(One exercise during each training session; 4 minutes and 5×30
seconds each)
Planting and cutting movements
Jump shot landings
Balance
(On a balance mat or wobble board, one exercise during each
training session; 4 minutes and 2×90 seconds each)
Passing the ball (two leg stance)
Squats (one or two leg stance)
Passing the ball (one leg stance)
Bouncing the ball with eyes closed
Pushing each other off balance
Strength and power
(2 minutes and 3×10 repetitions each)
One quadriceps exercise:
Squats to 80° of knee flexion
Bounding strides (Sprunglauf)
Forward jumps
Jump shot
two legged landing
“Nordic hamstring lowers” (2 minutes and 3×10 repetitions
each)
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relative risk of the number of injured players according to the
intention to treat principle to compare the risk of an injury in the
intervention and control groups. Cox regression was our analy-
sis tool for the primar y outcome as well as the secondary
outcomes, and we used the robust calculation method of the
variance-covariance matrix,
16
taking into account the cluster ran-
domisation. We tested rate ratios with Wald’s test. We used one
way analysis of variance to estimate the intracluster correlation
coefficient to obtain estimates of the inflation factor for
comparison with planned sample size. We used the inverse of the
difference between percentages of injured players in the two
groups to calculate the number needed to treat to save one
injury. We calculated exposures to training and matches and
incidence of injury as described in our earlier study.
We used a z test based on the Poisson model to compare the
rate ratio between the two groups (intervention v control), sex
(female v male), severity of injury (slight, minor, moderate,
major), and club activities (match, training).
Compliance and incidence of injury are presented as means
with standard errors. Relative risk and rate ratio are presented
with 95% confidence intervals. We regarded two tailed P values
0.05 as significant.
Results
Figure 3 shows the flow of clubs and players through the trial.
Players in the two groups were similar in sex distribution, age,
and dropout rates (table 1). All but eight (13%) of the clubs in the
intervention group used the programme of warm-up exercises
used to prevent injuries during the study period. Also, 13 (22%)
of the clubs in the control group used specific exercises intended
to prevent injuries (including training on the balance mat and
wobble board) as a part of their training.
Fig 1 Top: mat exercise. Middle: wobble board exercise. Bottom: mat pair
exercise
Fig 2 Example of a strength exercise (“Nordic hamstring lowers”). Top: start
position; a partner holds around the player’s ankles. Bottom: The player falls
slowly forwards, using hamstrings to resist the fall against the floor as long as
possible
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Injury characteristics
During the eight month season, 262 (14%) of the 1837 players
who were included in the study contracted a total of 298 injuries.
Of these, 241 (81%) were acute injuries and 57 (19%) were over-
use injuries. Table 2 shows the location of the most common
body part injured, the type of acute and overuse injur ies, and the
age of the injured players.
Effect of prevention
Significantly fewer injured players were in the intervention
group than in the control group for injuries overall, lower limb
injuries, acute knee or ankle injuries, and acute knee and upper
limb injuries, whereas a 37% reduction in acute ankle injuries did
not reach significance (table 3). The degrees of clustering at the
club level (intracluster correlation coefficient) were estimated to
be 0.043 to 0.071. The number needed to treat to prevent one
injury varied from 11 to 59 players.
The exposure in hours for the intervention group was 93 812
(11 210 hours spent in matches, 82 602 hours in training) and in
the control group 87 483 hours (10 783 hours in matches,
Box 3: Operational definitions used in the registration of
injury
Reportable injury
An injury occurred during a scheduled match or training session,
causing the player to require medical treatment or miss part of or
the next match or training session
Player
A player was entered into the study if she or he was aged 15-17
years (born between 1 January 1985 and 31 December 1987),
was registered on the club roster by the coach, and did not have a
major injury at the start of the study
Return to participation
The player was defined as injured until he or she was able to
participate fully in club activities (match and training sessions)
Type of injury
Acute
injury with a sudden onset associated with a known
trauma
Overuse
injury with a gradual onset without any known trauma
Severity†
Slight
0 days of absence and able to participate fully in the next
match or training session
Minor
absence from match or training for 1-7 days
Moderate
absence from match or training for 8-21 days
Major
absence from match or training for > 21 days
Exposure*
Match exposure
hours of matches
Training exposure
hours of training
In nearly all cases, players sustaining moderate or major injuries
were examined by a doctor. If there was any doubt about the
diagnosis the player was referred to a sport doctor or a sports
medicine centre for follow up, which often included imaging
studies or arthroscopic examination. In case of a slight or minor
injury, the player was often examined only by a physical therapist
or coach or not at all. None of the injured players was examined
or treated by any of the authors, and we had no influence on the
time it took a player to return to club activities.
Table 1 Characteristics of participants and compliance of clubs. Values are
numbers (percentages) of participants unless otherwise indicated
Characteristic Intervention group (n=958) Control group (n=879)
Girls 808 (50.9) 778 (49.1)
Boys 150 (59.8) 101 (40.2)
Mean (SD) age in years* 16.3 (0.6) 16.2 (0.6)
Dropouts 68 (7.1) 51 (5.8)
Injury prevention programme:
Clubs 61† 13
Training sessions (SE,
range)
27 (12, 1-55)‡ 26 (7, 14-35)§
Average time spent per
session in minutes (SE)
18 (6)¶ 18 (9)**
Average attendance per
session in %
73†† 81‡‡
*Range 15-17 years in both groups.
†Eight (13%) of the clubs did not continue using the programme of warm-up exercises used
to prevent injuries after the initial intensive introduction period. They used the programme at
5 (SE 5, range 1-13) sessions during the first part of the season and then discontinued the
programme.
‡14 (SE 7, 1-30) in the first part of the season (September to December) and 13 (SE 7, 0-26)
in the second part (January to April).
§14 (SE 4, 7-20) in the first part and 12 (SE 3, 7-15) in second part.
¶20 (SE 5) in the first part v 16 (SE 7) in second part.
**18 (SE 9) minutes in both first and second part.
‡‡78% in the first part v 69% in second part.
††85% in the first part v 78% in second part.
Assessed for eligibility (145 clubs; about 2180 players)
Randomised (123 clubs; 1886 players)
Control group
(61 clubs; 898 players)
Intervention group
(62 clubs; 988 players)
Declined to participate (22
clubs; about 294 players)
Excluded (2 clubs; 19 players)Excluded (1 club; 30 players)
Analysed (59 clubs; 879 players)Analysed (61 clubs; 958 players)
Fig 3 Flow of club clusters and players through the study. After randomisation,
two clubs in the control group withdrew from participating in the Norwegian
Handball Federation league (no players played for these clubs), and one club in
the intervention group declined to participate in the study. The players (n=49) in
these clubs were excluded from the study
Table 2 Most common body part injured, most common type of acute and
overuse injuries, and age of the injured players. Values are numbers
(percentages) of participants unless otherwise indicated
Intervention group (n=958) Control group (n=879)
Body category:
Ankle 31 (30.1) 47 (24.1)
Knee 25 (24.3) 44 (22.6)
Finger 10 (9.7) 22 (11.3)
Head 7 (6.8) 11 (5.6)
Low back 7 (6.8) 9 (4.6)
Shoulder 4 (3.9) 11 (5.6)
Acute injuries:
Sprains 48 (56.5) 75 (48.1)
Contusions 15 (17.6) 30 (19.2)
Fractures 8 (9.4) 18 (11.5)
Strains 6 (7.1) 11 (7.1)
Overuse injuries:
Anterior lower leg pain
(periostitis)
5 (27.8) 20 (51.3)
Knee pain 5 (27.8) 6 (15.4)
Low back pain 3 (16.7) 5 (12.8)
Mean (SD) age of injured
players in years*
17.3 (0.7) 17.1 (0.7)
*Range 15-18 years in both groups.
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76 700 hours in training). Table 4 shows the severity of injury for
different types of injury. Injuries overall, acute injuries, and acute
knee or ankle injuries differed significantly, whereas reductions
in 7-53% for slight injuries and 18-59% in minor injuries did not
reach significance. The overall difference in the incidence of
match and training injuries was also significant, whereas acute
injuries and acute knee or ankle injuries differed only for
matches (table 5). The 13 control clubs using training exercises to
prevent injuries had a significantly lower incidence of injuries
than the clubs in the control group doing no prevention training
(rate ratio: all injuries 0.48, 95% confidence interval 0.31 to 0.73,
P < 0.001; lower limb injuries 0.35, 0.19 to 0.63; P = 0.001; acute
injuries 0.47, 0.29 to 0.76; P = 0.002; acute knee or ankle injuries
0.22, 0.09 to 0.55; P = 0.001). No category of injury differed by
sex.
Discussion
The rate of injuries in adolescent athletes using a structured
warm-up programme as a part of their training improved clini-
cally and statistically, especially the rate of severe injuries to the
knee and ankle. The reduction in the relative risk is highly
significant and has been adjusted for the cluster sampling, which
takes into account the analytical limitations of a cluster
randomised study. As far as we are aware, our study is the first
randomised controlled trial among adolescents with a sufficient
sample size to show that acute knee or ankle injuries can be
reduced by 50% and severe injuries even more.
Data validation
The trial took place in the divisions comprising 16 year and 17
year olds from large geographical regions of Norway and
Table 3 Intention to treat analysis. Values are numbers (percentages) of injured players
Intervention group
(n=958)
Control group
(n=879)
Intracluster
correlation coefficient Inflation factor
Number
needed to
treat Relative risk (95% CI)*
P value (Wald’s
test)
All injuries 95 (9.9) 167 (19.0) 0.043 1.6 11 0.49 (0.36 to 0.68) <0.0001
Lower limb injuries 66 (6.9) 115 (13.1) 0.050 1.7 16 0.51 (0.36 to 0.73) <0.001
Acute knee or ankle injuries: 46 (4.8) 76 (8.6) 0.057 1.8 26 0.53 (0.35 to 0.81) 0.004
Acute knee injuries 19 (2.0) 38 (4.3) 0.071 2.0 43 0.45 (0.25 to 0.81) 0.007
Acute ankle injuries 28 (2.9) 40 (4.6) 0.071 2.0 59 0.63 (0.36 to 1.09) 0.097
Upper limb injuries 17 (1.8) 39 (4.4) 0.071 2.0 38 0.37 (0.20 to 0.69) 0.002
*Cox model calculated according to method of Lin and Wei,
17
which takes cluster randomisation into account.
Table 4 Numbers and severity of injuries
Intervention group (n=958) Control group (n=879) Rate ratio (95% CI)* P value (z test)
All injuries: 103 195 0.49 (0.39 to 0.63) <0.0001
Match 56 112 0.48 (0.35 to 0.66) <0.0001
Training 47 83 0.53 (0.37 to 0.75) <0.001
Slight 4 8 0.47 (0.14 to 1.55) 0.21
Minor 47 62 0.71 (0.48 to 1.03) 0.07
Moderate 20 56 0.33 (0.20 to 0.55) <0.0001
Major 32 69 0.43 (0.28 to 0.66) <0.0001
Overuse injuries: 18 39 0.43 (0.25 to 0.75) 0.003
Slight 0 3
Minor 4 9 0.41 (0.13 to 1.35) 0.14
Moderate 7 12 0.54 (0.21 to 1.38) 0.2
Major 7 15 0.44 (0.18 to 1.07) 0.07
Acute injuries: 85 156 0.51 (0.39 to 0.66) <0.0001
Slight 4 5 0.76 (0.20 to 2.78) 0.66
Minor 43 53 0.75 (0.51 to 1.13) 0.17
Moderate 13 44 0.28 (0.15 to 0.51) <0.0001
Major 25 54 0.43 (0.27 to 0.69) 0.001
Contact 51 82 0.58 (0.41 to 0.82) 0.002
Non-contact 34 74 0.43 (0.29 to 0.64) <0.0001
Acute knee or ankle injuries: 48 81 0.55 (0.39 to 0.79) 0.001
Slight 3 3 0.93 (0.19 to 4.62) 0.93
Minor 22 25 0.82 (0.46 to 1.46) 0.5
Moderate 8 25 0.30 (0.13 to 0.66) 0.003
Major 15 28 0.50 (0.27 to 0.94) 0.03
Knee ligament injuries 3†‡ 14‡§ 0.20 (0.06 to 0.70) 0.01
Meniscus injuries 2 7 0.27 (0.06 to 1.28) 0.1
Players with two or more injuries 8 19 0.39 (0.17 to 0.90) 0.03
Re-injury¶ 0 3
*Rate ratio obtained from Poisson model.
†Anterior cruciate ligament: n=3.
‡Anterior cruciate ligament (n=10), posterior cruciate ligament (n=3), medial collateral ligament (n=1).
§10 of the 16 ligament injuries to the cruciate ligament also included concomitant injuries to the medial collateral ligament, lateral collateral ligament, bone bruise, or meniscus injuries, or a
combination of these.
¶Same type and location of injury.
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recruited 85% of eligible players organised by the Norwegian
Handball Federation in these areas.
The external validity of the trial should therefore be high. As
we found no differences between the two groups at baseline, in
dropout rates, and in exposure during the study, the internal
validity should also be high. We discussed the reliability and
validity of injury and exposure registration in detail in an earlier
study, and our method should ensure good reliability and valid-
ity of the injury and exposure data and also good reliability for
comparing the data between the intervention and the control
groups.
Compliance
On comparison with a previous study that investigated the
prevention of injuries to the anterior cruciate ligament at the
senior level,
10
we found a considerably higher compliance (87%)
among the youth clubs. In view of the media attention focusing
on the problem of injuries to the anterior cruciate ligament in
women’s team handball, we were surprised to find that only 29%
of the clubs participating in a similar non-randomised study of
adult players fulfilled the compliance criteria.
10
However, this
study, and our intervention study, may have motivated some of
the youth clubs to include exercises to prevent injuries as a regu-
lar part of their training programme, as evidenced by the crosso-
ver observed in 22% of the control clubs. In support of the study
findings, these clubs had a significantly lower incidence of
injuries than the other control clubs. Also, not all clubs continued
to use the programme of warm-up exercises used to prevent
injuries after the initial intensive introduction period. However,
we included all the clubs in an intention to treat analysis, which
means that the effect of the programme may be even higher than
we have reported.
Structured programme of warm-up exercises to prevent
injuries
The exercises used in the programme were developed on the
basis of previous intervention studies in team handball
10 11
and
other sports,
8–9 12
and had been feasibility tested and modified to
be suitable for team handball. The focus on alignment of the hip,
knee, and ankle
especially the knee over toe position
was sup-
ported by data from Ebstrup and Boysen-Moller
17
and Olsen et
al.
18
Their video analyses of the mechanisms for injuries of the
anterior cruciate ligament in team handball indicate that players
could benefit from not allowing the knee to sag medially during
plant and cut movements or when suddenly changing speed.
The programme therefore focused on the proper technique for
planting and cutting movements, aiming at a narrower stance as
well as a knee over toe position. Recent data from a study inves-
tigating the prevention of injuries to the anterior cruciate
ligament among adult women’s team handball players indicate
that a programme of balance and cutting exercises focusing on
knee control not only prevents injuries
10
but also improves
dynamic balance and that this effect is maintained for at least 12
months.
19
One randomised study from senior men’s elite soccer
also showed a substantial decrease in the rate of injuries to the
anterior cruciate ligament as a result of a static balance training
programme using a balance board.
8
The prevention programme that we tested is multifaceted
and considers many aspects that could be related to the risk for
injury (agility, balance, strength, awareness of vulnerable
positions of the knee and ankle, playing technique), and it is not
possible to determine exactly which part of the programme may
be effective in preventing injuries to the knee and ankle. Based
on data from volleyball,
20
our programme also focused on land-
ing on both legs after jumps rather than just one leg, and with an
emphasis on increased hip and knee flexion to attenuate the
landing. The programme also included a strength exercise, the
“Nordic hamstring lower” exercise, which has been shown to be
effective in improving eccentric hamstring muscle strength
among adult male soccer players.
21
Since the hamstrings can act
as agonists to the anterior cruciate ligament during stop and
jump tasks,
20 22 23
it is possible that stronger hamstring muscles
can prevent injuries to the ligament, but this theory has never
been tested. Further studies are needed to determine what the
key component(s) of the programme are in reducing risk of
injury, and it seems warranted to examine the physiological
effects of each programme component, as well as the effect on
injury risk. In this way it may be possible to develop even more
specific programmes that require less time and effort and may be
suitable for “weekend recreational” athletes too.
Although injuries to the anterior cruciate ligament are a par-
ticular concern, especially in women’s pivoting sports, it was not
possible to plan this investigation on young players to determine
the effect of the intervention programme on rates of injury to the
anterior cruciate ligament alone. Our power calculations
indicated that a study looking at ruptures of the anterior cruciate
ligament would have needed 12 000 players in each group to
detect a 50% reduction in such injuries. Even so, we found an
80% reduction in ruptures of knee ligaments (anterior cruciate
ligament, posterior cruciate ligament, and medial collateral liga-
ment) in the intervention group, which reached significance.
Generalisability
We used youth team handball (age 15-17) as a case of youth
sports in our trial. Since the intervention was implemented for
both sexes and at different levels, the result indicates that the
youth elite as well as the intermediate and recreational players
would benefit from using the warm-up programme to prevent
injuries. We do not know if the results can be generalised to other
age groups or to other youth sports such as football, basketball,
or volleyball. However, these sports have a high incidence and
similar pattern of knee and ankle injuries, and the injury mecha-
nisms are also comparable (most injuries resulting from pivoting
and landing movements). Therefore it seems reasonable to
Table 5 Number of acute injuries, acute knee or ankle injuries, and incidence of injuries during matches and training. Incidence is reported as the number of
injuries per 1000 player hours, with standard errors
Intervention group (n=958) Control group (n=879) Rate ratio (95% CI)* P value (z test)
Injuries Incidence Injuries Incidence
No of acute injuries: 85 0.9 (0.08) 156 1.8 (0.06) 0.51 (0.39 to 0.66) <0.0001
Match 53 4.7 (0.06) 111 10.3 (0.04) 0.46 (0.33 to 0.64) <0.0001
Training 32 0.4 (0.14) 45 0.6 (0.12) 0.66 (0.42 to 1.04) 0.07
No of acute knee or ankle injuries: 48 0.5 (0.11) 81 0.9 (0.09) 0.55 (0.39 to 0.79) 0.001
Match 28 2.5 (0.06) 57 5.3 (0.06) 0.47 (0.30 to 0.74) 0.001
Training 20 0.2 (0.18) 24 0.3 (0.17) 0.78 (0.43 to 1.41) 0.41
*Rate ratio obtained from Poisson model.
Papers
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assume that the prevention programme used in the present
study also could be modified to be used in other similar sports.
Moreover, if the goal is to develop movement patterns that are
more resistant to injury, it may be easier to work with even
younger players who have not yet established their motion
patterns. Therefore, we suggest that programmes focusing on
technique (cutting and landing movements) and balance training
(on wobble boards, mats or similar equipments) are imple-
mented in players as young as 10-12 years.
Conclusion
A structured warm-up programme designed to improve
awareness and control of knees and ankles dur ing landing and
pivoting movements reduces injuries to the lower limb in youth
team handball. Preventive training should therefore be
introduced as a natural part of youth sports training
programmes in similar pivoting sports.
Acknowledgements: We thank the physiotherapists, instructors, coaches,
and players who participated in this study and Norwegian Handball
Federation staff and officials for practical support.
Contributors: OEO, GM, LE, IH, and RB contributed to study conception
and design. OEO coordinated the study and managed all aspects of the
trial, including developing, testing, and finalising the intervention, and data
collection. IH conducted and initialised the blinded data analyses, which
were planned and checked with OEO. OEO and RB wrote the fir st draft of
the paper, and all authors contributed to the final manuscript. OEO is
guarantor.
Funding: The Oslo Sports Trauma Research Center has been established at
the Norwegian University of Sport and Physical Education through gener-
ous grants from the Royal Norwegian Ministry of Culture, the Norwegian
Olympic Committee and Confederation of Sport, Norsk Tipping, and
Pfizer. In addition, this study was supported by grants from the Norwegian
Sports Medicine Foundation, the Norwegian Handball Federation, and If
insurance.
Ethical approval: Ethical approval was not required by the regional
committee for medical research ethics.
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(Accepted 30 November 2004)
doi 10.1136/bmj.38330.632801.8F
Oslo Sports Trauma Research Center, Norwegian University of Sport and Physical
Education, 0806 Oslo, Norway
Odd-Egil Olsen research fellow
Grethe Myklebust research fellow
Lars Engebretsen professor
Ingar Holme professor
Roald Bahr professor
Correspondence to: O E Olsen odd-egil.olsen@nih.no
What is already known on this topic
Sports injuries constitute 10-19% of all acute injuries
treated in emergency departments, with injuries to the knee
and ankle the most common types
The risk of serious knee injur ies, such as injuries to the
anterior cruciate ligament, is high among adolescents
playing pivoting sports such as football, basketball, or team
handball
It may be possible to reduce the incidence of knee and
ankle injuries among young people, but studies showing
this have been small and mainly non-randomised, with
significant methodological limitations
What this study adds
A structured warm-up programme designed to improve
awareness and knee and ankle control during landing and
pivoting movements prevents knee and ankle injuries
among youth athletes
The incidence of knee and ankle injuries can be reduced by
at least 50%
Preventive training should be routine in training
programmes for adolescents in pivoting sports
Papers
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... The risk of injury in handball is high, and adolescent players have reported injury rates of 8.3 to 40.7 injuries per 1000 match hours and 0.6 to 3.7 injuries per 1,000 training hours [1][2][3][4]. Shoulder and knee injuries are among the most frequent and burdensome [1][2][3][4][5][6]. ...
... The risk of injury in handball is high, and adolescent players have reported injury rates of 8.3 to 40.7 injuries per 1000 match hours and 0.6 to 3.7 injuries per 1,000 training hours [1][2][3][4]. Shoulder and knee injuries are among the most frequent and burdensome [1][2][3][4][5][6]. ...
... The Knee Group had 31% lower rate of knee injury than the Control Group, which is in line with previous studies in handball and other team sports [2,9,10,21]. The effect of Knee Control on knee injuries is thus somewhat lower than expected based on a previous study of Knee Control in similar-aged female football players in Sweden and a recent meta-analysis [8,9], and there can be several explanations for this. ...
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Background The risk of injury in adolescent handball is high, and shoulder and knee injuries are among the most frequent and burdensome. The Swedish Knee Control programme reduced the risk of anterior cruciate ligament injuries in female youth football players and traumatic knee injuries in male and female youth floorball players. However, to date, Knee Control has not been evaluated in an elite youth sport setting. The literature on the prevention of shoulder injuries in sport is scarce, and there are to our knowledge no previous studies evaluating the preventative efficacy of injury prevention exercise programmes (IPEPs) on shoulder injuries in adolescent handball players. Objectives To study the preventive efficacy of IPEPs on shoulder and knee injuries in adolescent elite handball players. Methods Eighteen Swedish handball-profiled secondary schools (clusters) with players aged 15–19 years, 54% males were randomised into either the Shoulder Group or Knee Group (interventions) or a Control Group. Players in the Shoulder Group were instructed to perform the Shoulder Control programme, and players in the Knee Group to perform the Knee Control programme, three times per week during May 2018 to May 2019. Control Group players continued their usual training. Outcomes were shoulder and knee injuries defined by the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. Intention-to-treat analyses were performed using Cox regression models with hazard rate ratios (HRRs) with corresponding 95% confidence intervals (CI). Results Six clusters (199 players) in the Shoulder Group, six clusters (216 players) in the Knee Group and six clusters (212 players) in the Control Group were included. There were 100 shoulder injuries and 156 knee injuries. The Shoulder Group had a 56% lower shoulder injury rate, HRR 0.44 (95% CI 0.29 to 0.68), and the Knee Group had a 31% lower knee injury rate, HRR 0.69 (95% CI 0.49 to 0.97) than the Control Group. The absolute risk reduction was 11% and 8%, and the number needed to treat was 9 and 13, respectively. Conclusions Adolescent elite handball players who performed the Shoulder Control and the Knee Control programmes had a lower risk of shoulder and knee injuries, respectively, than players who continued their usual training. Further research on how these two programmes can be combined to reduce knee and shoulder injuries in a time effective way is warranted. Trial registration ISRCTN15946352. Key points The burden of knee and shoulder injuries in handball is high. The Shoulder Control programme reduces the risk and overall burden of shoulder injuries in adolescent elite handball players. The Knee Control programme reduces the risk and overall burden of knee injuries in adolescent elite handball players.
... The natures of interventions in the selected studies were multicomponent (Barboza et al., 2019;Olsen et al., 2005), Fédération Internationale de Football Association (FIFA) 11+ (Beaudouin et al., 2019;Longo et al., 2012;Owoeye et al., 2014;Rossler et al., 2018;Soligard et al., 2008), neuromuscular training (Emery & Meeuwisse, 2010;LaBella et al., 2011), Medical Assessment and Research Center (F-MARC) (Junge et al., 2002;Stefen et al., 2008), educational (Scase et al., 2006), and stability (Wedderkopp et al., 1999). These interventions have used different principles of motor learning in practice design that are summarized below (see Table 2 for more information about the applications of concepts in different studies). ...
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This study aimed to review the scope of overuse injury prevention programs in young players through the lens of application of motor learning principles. From 280 studies found in the initial search, 13 studies were selected based on a series of inclusion criteria. The selected studies were categorized based on the type of intervention resulting in multicomponent (two studies), Fédération Internationale de Football Association 11+ (five studies), neuromuscular training (two studies), Fédération Internationale de Football Association Medical Assessment and Research Center (two studies), educational (one study), and stability (one study). The studies that had an effective preventative role to reduce overuse injuries applied some principles of motor learning to their intervention, such as contextual interference, variability of practice, task constraints, the power law of practice, transfer of learning, and explicit methods. There is a gap in the literature related to explicit applications of motor learning principles in the design of preventative interventions for overuse injury.
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Objective. —To encourage increased participation in physical activity among Americans of all ages by issuing a public health recommendation on the types and amounts of physical activity needed for health promotion and disease prevention.
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OBJECTIVE--To encourage increased participation in physical activity among Americans of all ages by issuing a public health recommendation on the types and amounts of physical activity needed for health promotion and disease prevention. PARTICIPANTS--A planning committee of five scientists was established by the Centers for Disease Control and Prevention and the American College of Sports Medicine to organize a workshop. This committee selected 15 other workshop discussants on the basis of their research expertise in issues related to the health implications of physical activity. Several relevant professional or scientific organizations and federal agencies also were represented. EVIDENCE--The panel of experts reviewed the pertinent physiological, epidemiologic, and clinical evidence, including primary research articles and recent review articles. CONSENSUS PROCESS--Major issues related to physical activity and health were outlined, and selected members of the expert panel drafted sections of the paper from this outline. A draft manuscript was prepared by the planning committee and circulated to the full panel in advance of the 2-day workshop. During the workshop, each section of the manuscript was reviewed by the expert panel. Primary attention was given to achieving group consensus concerning the recommended types and amounts of physical activity. A concise \"public health message was developed to express the recommendations of the panel. During the ensuing months, the consensus statement was further reviewed and revised and was formally endorsed by both the Centers for Disease Control and Prevention and the American College of Sports Medicine. CONCLUSION--Every US adult should accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the weekType: CONSENSUS DEVELOPMENT CONFERENCEType: JOURNAL ARTICLEType: REVIEWLanguage: Eng
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The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.
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Objective: To encourage increased participation in physical activity among Americans of all ages by issuing a public health recommendation on the types and amounts of physical activity needed for health promotion and disease prevention. Participants: A planning committee of five scientists was established by the Centers for Disease Control and Prevention and the American College of Sports Medicine to organize a workshop. This committee selected 15 other workshop discussants on the basis of their research expertise in issues related to the health implications of physical activity. Several relevant professional or scientific organizations and federal agencies also were represented. Evidence: The panel of experts reviewed the pertinent physiological, epidemiologic, and clinical evidence, including primary research articles and recent review articles. Consensus process: Major issues related to physical activity and health were outlined, and selected members of the expert panel drafted sections of the paper from this outline. A draft manuscript was prepared by the planning committee and circulated to the full panel in advance of the 2-day workshop. During the workshop, each section of the manuscript was reviewed by the expert panel. Primary attention was given to achieving group consensus concerning the recommended types and amounts of physical activity. A concise "public health message" was developed to express the recommendations of the panel. During the ensuing months, the consensus statement was further reviewed and revised and was formally endorsed by both the Centers for Disease Control and Prevention and the American College of Sports Medicine. Conclusion: Every US adult should accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the week.
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Women's participation in intercollegiate athletics has increased dramatically in recent years. Greater participation has increased awareness of health and medical issues specific to the female athlete. Some reports have noted a higher susceptibility to knee injury, specifically injuries to the anterior cruciate ligament, in female athletes as compared with their male counterparts. We performed a 5-year evaluation of anterior cruciate ligament injuries in collegiate men's and women's soccer and basketball programs using the National College Athletic Association Injury Surveillance System. Results showed significantly higher anterior cruciate ligament injury rates in both female sports compared with the male sports. Noncontact mechanisms were the primary cause of anterior cruciate ligament injury in both female sports. Possible causative factors for this increase in anterior cruciate ligament injuries among women may be extrinsic (body movement, muscular strength, shoe-surface interface, and skill level) or intrinsic (joint laxity, limb alignment, notch dimensions, and ligament size).
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Proprioceptive training has been shown to reduce the incidence of ankle sprains in different sports. It can also improve rehabilitation after anterior cruciate ligament (ACL) injuries whether treated operatively or nonoperatively. Since ACL injuries lead to long absence from sports and are one of the main causes of permanent sports disability, it is essential to try to prevent them. In a prospective controlled study of 600 soccer players in 40 semiprofessional or amateur teams, we studied the possible preventive effect of a gradually increasing proprioceptive training on four different types of wobble-boards during three soccer seasons. Three hundred players were instructed to train 20 min per day with 5 different phases of increasing difficulty. The first phase consisted of balance training without any balance board; phase 2 of training on a rectangular balance board; phase 3 of training on a round board; phase 4 of training on a combined round and rectangular board; phase 5 of training on a so-called BABS board. A control group of 300 players from other, comparable teams trained "normally" and received no special balance training. Both groups were observed for three whole soccer seasons, and possible ACL lesions were diagnosed by clinical examination, KT-1000 measurements, magnetic resonance imaging or computed tomography, and arthroscopy. We found an incidence of 1.15 ACL injuries per team per year in the proprioceptively trained group (P < 0.001). Proprioceptive training can thus significantly reduce the incidence of ACL injuries in soccer players.