This outstanding body of research is a watershed in the fight against
ACL-injuries. This group should be richly commended for this excellent
work.
The work points to (a priori) how, in the case of alpine skiing,
excessive abduction loading / valgus torque of the lower leg structure
relative to the upper leg (about the knee) can be truncated by "detaching"
the imposing load from the point of load application at t...
This outstanding body of research is a watershed in the fight against
ACL-injuries. This group should be richly commended for this excellent
work.
The work points to (a priori) how, in the case of alpine skiing,
excessive abduction loading / valgus torque of the lower leg structure
relative to the upper leg (about the knee) can be truncated by "detaching"
the imposing load from the point of load application at the playing
surface in the direction of the applied load. E.G., if the medial load
that applies abduction to the lower leg can be "released" from the lower
leg -- the abduction / valgus loading will dissipate. An alpine ski-
binding with this capability (via lateral heel release) will provide this
capability when the applied load is "released" (when the applied abduction
load approaches a pre-determined level that is well below the elastic
limit of the acl but which level is above that which is needed to provide
"controlled" skiing maneuvers). Such a binding exists, today, and a
prospective intervention study should be considered to study its merits
for skiers.
Rick Howell, CEO, Howell Product Development, Inc., Stowe, Vermont, USA
Conflict of Interest:
Inventor of alpine ski-binding with independently adjustable, non-inadvertant abduction release in response to excessive valgus loading, but am presently cut-off from financial gain in this IP due to on-going litigation re ownership rights.
I read your fascinating article with much interest. Do you think that in simple terms that anticipatory regulation may be an aspect of the decision-making the athlete makes before execution of an action. In the instance of longer duration exercise eg a marathon a decision is made then physiological systems amongst others come into action as you have described.
Prior learning and adaptation may be involved as well as genetic and en...
I read your fascinating article with much interest. Do you think that in simple terms that anticipatory regulation may be an aspect of the decision-making the athlete makes before execution of an action. In the instance of longer duration exercise eg a marathon a decision is made then physiological systems amongst others come into action as you have described.
Prior learning and adaptation may be involved as well as genetic and environmental factors.
The particular learning aspects include; cognition, perception and affection.
The knowledge to be gained from this study could have particular importance to injury prevention in sport, notably when fatigue is an issue. Central fatigue and peripheral fatigue.
Henare Broughton
PhD candidate
School of Psychology
Trinity College Dublin
Ireland.
Age cheats are a common problem in Youth Tournaments in Sub
Saharan Africa with poor record keeping practices in rural
areas.
The MRI will help greatly in our quest to stamp out age cheats
but more research needs to be done to determine the
sensitivity of the MRI in determining ages of African Athletes
as current evidence shows that there may be some false
positives going by the current grading system. Some scientists
ar...
Age cheats are a common problem in Youth Tournaments in Sub
Saharan Africa with poor record keeping practices in rural
areas.
The MRI will help greatly in our quest to stamp out age cheats
but more research needs to be done to determine the
sensitivity of the MRI in determining ages of African Athletes
as current evidence shows that there may be some false
positives going by the current grading system. Some scientists
argue that the environment and nutritional differences across
Africa might delay fusion of the wrist. As such more research
needs to be done to develop a more accurate grading system.
We thank Professor Thornton for raising these issues and are grateful
for the opportunity to clarify details of the trial protocol and analysis.
There is, in fact, no discrepancy between the description of outcomes
in the trial protocol published on the trial web site, the protocol that
was registered on the Australian New Zealand Clinical Trials Registry, and
the report published in the British Journal of Sports...
We thank Professor Thornton for raising these issues and are grateful
for the opportunity to clarify details of the trial protocol and analysis.
There is, in fact, no discrepancy between the description of outcomes
in the trial protocol published on the trial web site, the protocol that
was registered on the Australian New Zealand Clinical Trials Registry, and
the report published in the British Journal of Sports Medicine. All three
sources describe the same primary outcomes (risk of soreness and time to
injury) and the same secondary outcomes (severity of soreness, time to
("preventable") muscle/ligament/tendon injuries, time to injuries for
which professional care was sought, and perceptions of looseness during
and after exercise). In addition, all three sources describe the same
secondary analyses of the interactions between frequency of activity, age
and strength of belief in affects of stretching and each of the two
primary outcomes. Confusion may have arisen because in the trial report we
refer to the analysis of the interactions as "outcomes", although the
analyses of interactions were conducted on the same primary and secondary
outcomes as listed above. And we may have added to the confusion by
inconsistently referring to the perceptions of looseness during and after
exercise as either one or two outcomes. We acknowledge that the wording
may not have been clear but we reiterate that there was no inconsistency
between the analyses described in the protocol, register and trial report.
The protocol, register and trial report describe an analysis of the
subset of injuries which could plausibly be prevented by stretching. The
protocol (which is more detailed than the registry entry) indicated that
the classification of injuries into those that could and could not
plausibly be prevented by stretching would be classified by an independent
expert. We found that the data lacked sufficient detail to inform
decisions about whether individual injuries were preventable so we decided
simply to classify all muscle, ligament and tendon injuries as potentially
preventable. This decision was made before the allocation code was broken
without reference to the data. We did not know, at the time that decision
was made, that there would be a significant effect of stretching on the
subset of muscle, ligament and tendon injuries.
As the protocol indicated, no adjustment was made for multiple
comparisons. We interpret frequentist analyses as Bayesian analyses with
vague priors[1] and, from this perspective, the decision not to make
adjustments for multiple comparisons is justified. At any rate, there were
only two primary outcomes so adjustment for multiple comparisons would not
have changed the conclusions from the primary analysis. We agree that the
finding of an effect on the secondary outcome of muscle, ligament and
tendon injuries is less robust than the finding of an effect on the
primary outcome risk of soreness because muscle, ligament and tendon
injuries were a secondary outcome. That is why we concluded that
stretching "probably reduces the risk of some injuries and does reduce the
risk of bothersome soreness".
Reference
1. Barnett V (1973). Comparative Statistical Inference. London:
Wiley.
I read the review article on the anticipatory regulation of
performance and pacing strategies by Dr R Tucker in the June edition of
BJSM with great interest.
The idea that there is a part of the brain, as yet undiscovered,which
enables one to judge the optimal work rate for a given task, is an
intriguing one.
From a Darwinian view point, the idea of there being a template in the
brain that one could draw upon in determin...
I read the review article on the anticipatory regulation of
performance and pacing strategies by Dr R Tucker in the June edition of
BJSM with great interest.
The idea that there is a part of the brain, as yet undiscovered,which
enables one to judge the optimal work rate for a given task, is an
intriguing one.
From a Darwinian view point, the idea of there being a template in the
brain that one could draw upon in determining pacing strategy, carries
great merit.
Anthropologists have learnt of a hunting strategy used by Bushmen from
Southern Africa in which the prey, such as a Kudo, is chased for many
hours until it collapses in exhaustion. The Bushmen pace themselves, such
that they do not succumb to exhaustion, and are able to follow the tracks
of the animal when they lose sight of it.
The same principle can be seen with the hunting behaviour of wolves.
Having spotted a weak member of a herd of elk or other deer, they will
chase it for hours on end if necessary.
It is obvious that the most successful hunters will be those who can judge
their pace the best. The genes of these hunters are more likely to be
passed through to the next generation.
An athlete's ability to judge pace is therefore likely to be the
consequence of millions of years of mammalian evolution.
We have read with interest the recently reported accelerometer study
of physical activity in community-living seniors in Oxfordshire (1).
Subjects were observed for 7 days, apparently in the winter or the spring,
although the only clue to the important question of season is that
invitations were sent out over a 20-week period, beginning in September of
2006. In discussing their data, the authors claim (p...
We have read with interest the recently reported accelerometer study
of physical activity in community-living seniors in Oxfordshire (1).
Subjects were observed for 7 days, apparently in the winter or the spring,
although the only clue to the important question of season is that
invitations were sent out over a 20-week period, beginning in September of
2006. In discussing their data, the authors claim (p. 446) �gThis is the
first moderately sized population-based study of older people published to
date with objective PA measures and a broad range of health, psychological
and anthropometric variables.�h
In fact, a much more extensive community study of seniors aged 65-99
years has been conducted previously, in the Japanese community of
Nakanojo. Many of the key findings from the Nakanojo Study have been
published, and are summarized in a recent review (2). The Japanese
subjects were monitored 24 hours per day for an entire year, thus avoiding
problems from seasonal variations in physical activity (3-6). Perhaps in
part because seasonal effects are quite large in this age group, the
average step counts over the whole year were somewhat higher than the 6443
steps/day reported by Harris et al. (1), particularly in the male
subjects. It would be interesting to have for comparison British data that
also covers an entire year. Like Harris et al. (1), we found associations
of step counts with age, sex, body build, physical, metabolic and
psychological health among other environmental, geographic and psycho-
social variables, and our data support the view that in Asia, as in
Europe, many seniors are currently taking substantially less than the
recommended daily dose of physical activity.
Yukitoshi Aoyagi
REFERENCES
1. Harris TJ, Owen CG, Victor CR, et al. What factors are associated
with physical activity in older people, assessed objectively by
accelerometry? Br J Sports Med 2009; 43: 442-450.
2. Aoyagi Y, Shephard RJ. Steps per day. The road to senior health?
Sports Med 2009; 39: 423-438.
3. Togo F, Watanabe E, Park H, et al. Meteorology and the physical
activity of the elderly: the Nakanojo Study. Int J Biometeorol 2005; 50:
83-89.
4. Togo F, Watanabe E, Park H, et al. How many days of pedometer use
predict the annual activity of the elderly reliably? Med Sci Sports Exerc
2008; 40: 1058-1064.
5. Yasunaga A, Togo F, Watanabe E, et al. Sex, age, season, and
habitual physical activity of older Japanese: the Nakanojo Study. J Aging
Phys Act 2008; 16: 3-13.
6. Shephard RJ, Aoyagi Y. Seasonal variations in physical activity
and implications for human health. Eur J Appl Physiol 2009; in press. doi:
10.1007/s00421-009-1127-1.
We are concerned with an important confusion about data unit of
measurement presented by Girard et al. when evaluating the changes in
Lower Limbs Stiffness (LLS) during prolonged tennis playing (1).
Evaluation of LLS is of great interest in a sport like tennis where speed
and reactivity takes a great part. LLS is an important element of the
muscle biomechanical characteristics and the optimal utiliz...
We are concerned with an important confusion about data unit of
measurement presented by Girard et al. when evaluating the changes in
Lower Limbs Stiffness (LLS) during prolonged tennis playing (1).
Evaluation of LLS is of great interest in a sport like tennis where speed
and reactivity takes a great part. LLS is an important element of the
muscle biomechanical characteristics and the optimal utilization of the
stretch-shortening cycle requires some level of stiffness (2). Then an
appropriate level of stiffness is necessary for optimal performance and
prevention of injury (2). To evaluate LLS, Girard et al. used a
standardized procedure proposed by Dalleau et al. (3). This method allows
evaluation of LLS (expressed in N/m or in kN/m) in field conditions via
the measure of both flight and contact times during a multi-rebound test.
Such a procedure has been previously used in several sport activities and
results reported (4-5). However, in the article published by the British
Journal of Sports Medicine, the results are presented expressed in N/m/kg
while the correct unit is N/m or kN/m, as mentioned above. Comparison with
the range of previous LLS data reported in the literature (4-5) confirms
the confusion in the choice of unit by Girard et al. and suggests that it
should likely be in kN/m. Although not affecting the conclusion of the
authors concerning the relative changes in stiffness during prolonged
tennis playing, we would like the scientists interested in LLS evaluation
to be aware of this mistake in order to avoid a wrong interpretation of
the data presented and to permit their use for comparison with other
results.
S DURAND, A RAHMANI
References
1) Girard, O., Lattier, G., Micallef, J.-P., Millet, G.P. Changes in
exercise characteristics, maximal voluntary contraction, and explosive
strength during prolonged tennis playing. Br J Sports Med 40:521-526,
2006.
2) Butler, R.J., Crowel III, H.P., Mac Clay Davis, I. Lower extremity
stiffness: implications for performance and injury. Clin Biomech 18: 511-
517, 2003.
3) Dalleau, G., Belli, A., Viale, F., Lacour, J.-R., Bourdin, M. A
simple method for field measurements of leg stiffness in hopping. Int J
Sports Med. 25: 170-176, 2004.
4) Bret C., Rahmani, A., Dufour, A.-B., Messonnier, L., Lacour, J.-
R. Leg strength and stiffness as ability factors in 100m sprint running. J
Sports Med Phys Fitness. 42: 274-281, 2002.
5) Dalleau, G., Rahmani, A., Verkindt, C. Relationship between power
and musculotendinous stiffness in high level athletes. Sci Sports, 22: 110
-116, 2007.
We appreciate the thoughtful review of our manuscript by Hancock, Ste
-Marie and Young.(1) In this brief response, we reconsider the issues
raised in their review and continue the discussion of relative age effects
in National Hockey League (NHL) draftees.
REGARDING THE APPROPRIATE USE OF CUTOFF DATES.
Hancock et al. proposed that the more appropriate method for
examining relative ag...
We appreciate the thoughtful review of our manuscript by Hancock, Ste
-Marie and Young.(1) In this brief response, we reconsider the issues
raised in their review and continue the discussion of relative age effects
in National Hockey League (NHL) draftees.
REGARDING THE APPROPRIATE USE OF CUTOFF DATES.
Hancock et al. proposed that the more appropriate method for
examining relative age effects in NHL draft players was to use the age
cutoff criterion established by the NHL (September 16th). Our original
analyses(2) utilized the age cutoff from the Hockey Canada and Hockey USA
governing bodies (January 1st). Although the cutoff used by Hancock et al.
seems reasonable, we submit that our original analyses were more
appropriate because the proposed mechanisms of relative age effects are
known to originate early in an athlete’s development.(3)
In sport, relative age attainment differentials are proposed to
result from physical maturation differences among individuals during
growth and development. (4) Specifically, those born shortly after the cut
-off date established by sport governing bodies typically display more
mature physical characteristics compared to those born later in the year.
(5) Greater height, strength, speed and power not only relate to maturity,
but also provide physical attributes that underpin performance in many
sports. As a result, earlier-born, more mature individuals are more likely
to dominate youth sport, be identified as ‘outstanding’ and be selected by
scouts and coaches for representative sport competition. (4)
More competitive levels of sport participation are associated with
dramatic changes in the practice environment. Here, selected athletes
access practice more frequently and dedicate an increasingly significant
proportion of weekly time to training with more highly qualified and
specialized coaches to facilitate continued development. Thus selection
and access to quality practice propagate relative age effects well into
the senior years, explaining why discrepancies in birth date tendencies
have been reported repeatedly across professional sports.(4)
Interestingly, a recent meta-analysis by our research team found that
relative age effects were strongest in adolescence and diminished in
adulthood. (4)
In summary, the cutoff dates associated with early development drive
relative age effects, not the cutoff date used for the NHL draft. Altering
the cutoff date as we saw from Hancock et al. should have little influence
on the overall effect. Their re-analysis indicates the largest
representation was in birth quarter two followed by birth quarter three,
which, as they showed, corresponds better to a relative age effect
originating from the Hockey Canada and Hockey USA cutoff date of January
1st than September 1st.
REGARDING THE USE OF ALL DRAFT ROUNDS
Hancock et al criticized our choice to use all seven rounds of the
draft for our relative age analyses on the basis that later rounds are
made up of lower quality players. This seems like splitting hairs to us,
as this rationale could also be used to justify using only round one
instead of rounds two to four or the first 10 players of round one versus
the remaining 20 players in round one. Moreover, our paper was written to
demonstrate that the relative age effect explained some of the results for
the NHL draft, not the performance of the draftees after they had entered
the NHL. We defend our original choice on the basis that any selection in
the NHL represents a reasonable level of expertise to examine the relative
age effect in this population. Furthermore, and perhaps more interesting,
an additional analysis of our data comparing relative age distributions
for rounds one to four with rounds five to nine (up to 2005 the NHL draft
had nine rounds), noted a slightly stronger relative age effect in later
rounds than earlier rounds (Cramér’s V = 0.08 for rounds 1-4 and 0.13 for
rounds 5-9).
REGARDING DRAFT VERSUS OVERALL SELECTION FOR SPEARMAN CORRELATION
The rationale for using an athlete’s overall selection in the draft
versus round number is reasonable, as it adds additional depth to the
selection variable. However, coaches, athletes and spectators rarely talk
about athletes in terms of what their overall selection was – more often
the overall draft round number is the characteristic of interest. Teams
often have differing strategies for how they choose players in the draft
(e.g., drafting to win the Stanley Cup vs. drafting for team development).
As a result, players ranked highly by one team might not be considered at
all by another. Removing draft round number assumes a) that each team uses
the same strategy for how they choose their draft picks and b) that
players can be easily rank-ordered and are equivalent from team to team.
We defend our original analysis as being perhaps more relevant to the
specific practices used by each team during the draft, although we
appreciate the additional statistical depth that might be added by Hancock
et al.’s method. The lack of consistency between our analyses and theirs
is cause for concern, however, and we encourage future research in the
area to elucidate these contradictory findings.
In summary, these studies continue to highlight the effects of
secondary factors on long-term athlete development.
Joseph Baker
References
1. Hancock, D. J., Ste-Marie, D. M., Young, B. W. Birth date and
birth place effects in National Hockey League draftees 2000-2005: Comments
on Baker and Logan (2007). Br J Sports Med 2008; 42: 948-949.
2. Baker, J. Logan, A. J. Developmental contexts and sporting
success: Birthdate and birthplace effects in NHL draftees 2000-2005. Br J
Sports Med 2007; 41: 515-517.
3. Barnsley, R. H., Thompson, A. H. Birthdate and success in minor
hockey: The key to the NHL. Can J Behav Sci 1988; 20 167-176.
4. Cobley, S., Baker, J., Wattie, N. McKenna, J. Annual age grouping
and athlete development: A meta- analytical review of relative age effects
in sport. Sports Med 2009; 39 235-256.
5. Sherar LB, Baxter-Jones ADG, Faulkner RA, et al. Does physical
maturity and birth date predict talent in male youth ice hockey players? J
Sports Sci 2007; 25: 879-86
Knechtle and Kohler have considered the factors relating to overall
performance in triple ironman triathlon. There are however several other
considerations which must be made when looking at total race time.
The mental preparation needed for ultra-endurance events may have a
significant impact on total race time. This can limit training time and
total race time, especially if an individua...
Knechtle and Kohler have considered the factors relating to overall
performance in triple ironman triathlon. There are however several other
considerations which must be made when looking at total race time.
The mental preparation needed for ultra-endurance events may have a
significant impact on total race time. This can limit training time and
total race time, especially if an individual misjudges their pacing early
in the event.
Some consideration needs to be taken of pre-race injuries. Endurance
athletes commonly have a number of injuries which limit different aspects
of their preparation and race. With a sample size of only 17, these two
factors are likely to prevent any true assosciation between
anthropomorphic factors and total race time.
The study of triple ironman distance events is unusual as there are
few events of this type globally. Comparisons to marathon running, ironman
triathlon and cycling are perhaps misguided as these are all sports with
large numbers of competitors and a circuit of races for professional
athletes.
Subjects in this study trained between only 6 hours each week and up
to 55 hours. Skin fold thickness was high indicating a high body fat
percentage. Average weight was 85Kg, considerably higher than most
professional ironman triathletes. Competitors clearly varied considerably
in their preparation. They range between casual competitors and
professional athletes. This makes study of the factors needed for low
total race time difficult.
The use of performance in individual sections of the race may not be
a valid measurement to make alone. Whilst there is a trend towards time in
the running section being the best predictor of total race time, this is
in fact also a function of both cycling time and swimming time. The energy
expended in other sections of the event will take a toll on the later part
even with the best athletes. As the last section of the race the run is
most likely to show a trend.
Despite the thorough analysis made of the results, currently there is
insufficient participation in this type of event for this type of study.
As the popularity of ultra-endurance sport grows, the factors necessary
for optimum performance may more easily be delineated.
This is likely to be the definitive trial on the effectiveness of pre-exercise stretching for some time, so it is important that it is carefully reported and analysed. I have a few questions.
It is stated that “two primary outcomes and 12 secondary outcomes were specified a priori in the analysis plan” but only the two primary outcomes and five secondary outcomes appear in the paper. Four secondary...
This is likely to be the definitive trial on the effectiveness of pre-exercise stretching for some time, so it is important that it is carefully reported and analysed. I have a few questions.
It is stated that “two primary outcomes and 12 secondary outcomes were specified a priori in the analysis plan” but only the two primary outcomes and five secondary outcomes appear in the paper. Four secondary
endpoints (three reported in the paper) are listed in the trial protocol registered with the Australian and New Zealand Clinical Trial registry, accessible here http://www.anzctr.org.au/trial_view.aspx?ID=82520. Five
secondary endpoints (three reported in the paper) are listed in the protocol available on the trial website, accessible here http://www.kunnskapssenteret.no/The%20Stretching%20Trial. In that protocol the second of the two primary endpoints (time to injury) is subdivided in a number of ways that, with the exception of whether the
participant sought help from a professional, differ from the analyses reported.
The reported secondary analysis of “time to injuries to muscles, ligaments and tendons” differs from the pre-specified secondary outcome in both protocols of “time to injuries that might be considered could be
preventable by stretching”? In the website protocol it is stated that this “preventability” classification would be done without knowledge of the trial group. Can the authors clarify whether this was done?
Can they also clarify which outcomes were pre-specified in the analysis plan before the trial allocation code was broken, can they report
all these outcomes, and state what adjustment was made for multiple tests of statistical significance?
These questions may sound pedantic, but the primary outcome for injury was negative. The apparent effect on muscle ligament and tendon injuries was of only modest statistical significance (P=0.03), and might disappear if adjustment was made for multiple significance testing. The
apparent effect on the “bothersome soreness” is unavoidably susceptible to reporting bias in an open trial. The higher rate of dropout from follow-up at all time points in the experimental group, which appears unlikely to
be due to chance, might bias the results in either direction.
As a participant, I was impressed with the trial organisation and design. Without reassurance that analysis and reporting were of an equally high standard, I remain fearful that the authors’ conclusion that “stretching … probably reduces the risk of some injuries and does reduce
the risk of bothersome soreness”, is too strong.
This outstanding body of research is a watershed in the fight against ACL-injuries. This group should be richly commended for this excellent work.
The work points to (a priori) how, in the case of alpine skiing, excessive abduction loading / valgus torque of the lower leg structure relative to the upper leg (about the knee) can be truncated by "detaching" the imposing load from the point of load application at t...
We thank Professor Thornton for raising these issues and are grateful for the opportunity to clarify details of the trial protocol and analysis.
There is, in fact, no discrepancy between the description of outcomes in the trial protocol published on the trial web site, the protocol that was registered on the Australian New Zealand Clinical Trials Registry, and the report published in the British Journal of Sports...
I read the review article on the anticipatory regulation of performance and pacing strategies by Dr R Tucker in the June edition of BJSM with great interest. The idea that there is a part of the brain, as yet undiscovered,which enables one to judge the optimal work rate for a given task, is an intriguing one. From a Darwinian view point, the idea of there being a template in the brain that one could draw upon in determin...
Dear Editor
We have read with interest the recently reported accelerometer study of physical activity in community-living seniors in Oxfordshire (1). Subjects were observed for 7 days, apparently in the winter or the spring, although the only clue to the important question of season is that invitations were sent out over a 20-week period, beginning in September of 2006. In discussing their data, the authors claim (p...
Dear Editor
We are concerned with an important confusion about data unit of measurement presented by Girard et al. when evaluating the changes in Lower Limbs Stiffness (LLS) during prolonged tennis playing (1). Evaluation of LLS is of great interest in a sport like tennis where speed and reactivity takes a great part. LLS is an important element of the muscle biomechanical characteristics and the optimal utiliz...
Dear Editor
We appreciate the thoughtful review of our manuscript by Hancock, Ste -Marie and Young.(1) In this brief response, we reconsider the issues raised in their review and continue the discussion of relative age effects in National Hockey League (NHL) draftees.
REGARDING THE APPROPRIATE USE OF CUTOFF DATES.
Hancock et al. proposed that the more appropriate method for examining relative ag...
Dear Editors,
Knechtle and Kohler have considered the factors relating to overall performance in triple ironman triathlon. There are however several other considerations which must be made when looking at total race time.
The mental preparation needed for ultra-endurance events may have a significant impact on total race time. This can limit training time and total race time, especially if an individua...
Dear Editor
This is likely to be the definitive trial on the effectiveness of pre-exercise stretching for some time, so it is important that it is carefully reported and analysed. I have a few questions.It is stated that “two primary outcomes and 12 secondary outcomes were specified a priori in the analysis plan” but only the two primary outcomes and five secondary outcomes appear in the paper. Four secondary...
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