Stiffness as a Risk Factor for Achilles Tendon Injury in Running Athletes

18 Pages·2016·0.86 MB·English

SportsMed
DOI10.1007/s40279-016-0526-9
SYSTEMATIC REVIEW
Stiffness as a Risk Factor for Achilles Tendon Injury in Running
Athletes
Anna V. Lorimer1,2 • Patria A. Hume1
(cid:2)SpringerInternationalPublishingSwitzerland2016
Abstract increasedverticalandpropulsiveforceswereprotectivefor
Background Overuse injuries are multifactorial resulting Achilles tendon injuries and were also associated with
from cumulative loading. Therefore, clear differences increased lower body stiffness. Risk factors for Achilles
betweennormalandat-risk individualsmaynotbepresent tendon injuries that had unclear associations were also
for individual risk factors. Using a holistic measure that investigatedwiththeevidencetrendingtowardsanincrease
incorporatesmanyoftheidentifiedriskfactors,focusingon in leg stiffness and a decrease in ankle stiffness being
multiple joint movement patterns may give better insight detrimental to Achilles tendon health.
into overuse injuries. Lower body stiffness may provide Conclusion Fewstudieshaveinvestigatedthelinkbetween
such a measure. lower body stiffness and Achilles injury. High stiffness is
Objective Toidentifyhow riskfactorsfor Achilles tendon potentially associated with risk factors for Achilles tendon
injuries influence measures of lower body stiffness. injuries although some of the evidence is controversial.
Methods SPORTDiscus, Web of Science, CINAHL and Prospective injury studies are needed to confirm this rela-
PubMed were searched for Achilles tendon injury risk tionship. Large amounts of high-intensity or high-speed
factorsrelatedtovertical,legandjointstiffnessinrunning workorrunningonsoftsurfacessuchassandmayincrease
athletes. Achilles injury risk. Coaches and clinicians working with
Results Increased braking force and low surface stiffness, athletes with new or reoccurring injuries should consider
which were clearly associated with increased risk of training practices of the athlete and recommend reducing
Achilles tendon injuries, were also found to be associated speedorsandrunningifloadingisdeemedtobeexcessive.
with increased lower body stiffness. High arches and
Key Points
High braking forces and running on soft surfaces
such as sand have previously shown a clear increase
in risk for Achilles tendon injuries and were also
Electronicsupplementarymaterial Theonlineversionofthis
article(doi:10.1007/s40279-016-0526-9)containssupplementary associated with higher lower extremity stiffness
material,whichisavailabletoauthorizedusers. measures.
& AnnaV.Lorimer Factors shown to be protective for Achilles injury
[email protected];[email protected] were also associated with higher stiffness measures.
1 SportsPerformanceResearchInstituteNewZealand There is a potential link between high lower
(SPRINZ)atAUT-Millennium,AucklandUniversityof extremity stiffness measures and risk for Achilles
Technology,PrivateBag92006,Auckland,NewZealand
injuries, which warrants further prospective
2 UnitecInstituteofTechnology,139CarringtonRoad, investigation.
MtAlbert,Auckland1025,NewZealand
123
A.V.Lorimer,P.A.Hume
1 Introduction alternativemethodofassessinginjuryrisk[12].Dynamical
systems theory suggests that a movement’s end result can
be achieved by multiple movement patterns [13–16]. It is
Chronic Achilles tendon injuries, commonly referred to as
possiblethataninjuryendpointdoesnotarisefromasingle
tendinopathy or tendonitis (from here on referred to as
identifiable factor but from multiple factors working
Achillesinjures),areafrustratinginjuryforathletesowing
together to cause eventual breakdown of the tissue [15].
totheirslow recoverytime andtendency for reoccurrence.
Multiple combinations of multiple factors would give the
Whenclassifiedfor‘severity’basedonthenumberofdays
observedresultsforsingle-riskfactoranalysis,small-effect
offtrainingandprevalence,Achillesinjurieswerethemost
sizes with large confidence intervals. Identifying single
severe lower limb injuries, with only upper back injuries
measurements that are influenced by many of the known
more severe in elite triathletes [1, 2]. In club and devel-
risk factors, may provide a better measure of injury risk.
opment triathletes, Achilles injuries ranked as number one
While lower extremity stiffness does not reflect the prop-
on the severity scale [2].
ertiesofthetendon,itdoesreflecthowthedifferenttissues
Three main themes apparent in the literature regarding
and joints work together during the first half of stance
the mechanism of Achilles injury include tensile loading
phase. Lower extremity stiffness may therefore provide a
[3],shearing[4]andhyperthermia[5,6]. Foroveruse type
means of identifying factors causing stress to the tendon
tendon injuries, it has been suggested that ‘non-homolo-
tissue during functional movements without having to use
gousloading’leadstolocalisedtendondamageresultingin
morecomplexlocalizedmeasuressuchastendonstiffness.
an area of weakened tissue [7]. This area of weakened
Total leg stiffness during hopping had a potentially large
tissue gradually becomes larger if loading occurs before
negative effect size (-1.73 ± 1.71) when comparing
healing is complete, resulting in a cycle of progressively
Achilles injured and uninjured runners [12]. Single-leg
weakened anddysfunctionaltissue.Ex vivo cyclic loading
hoppingonasledapparatusresultedinsignificantlyhigher
has shown tendon stiffness decreases over time and hys-
vertical stiffness in a cohort of Achilles injured patients
teresis becomes greater, which is believed to indicate
compared with healthy volunteers [17]. Stiffness is also
accumulated damage [8]. It is unlikely that the natural
modified by many of the Achilles injury risk factors
motionof running wouldproduceforcesthat could leadto
identified [12]. A link between individual risk factor
macroscopic disruption of the tendon structure. It is con-
measures and stiffness variables, for example higher leg
ceivable, however, that injurious movement patterns lead
stiffness associated with higher braking forces and soft
tomicroscopicbutaccumulatingdamage,whichultimately
surfaces, would indicate a potential for the use of stiffness
results in pain and dysfunction for the athlete. Loading
as a more holistic measure of Achilles injury risk.
through the tendon during cycling is significantly lower
Stiffness is a pseudo measure relating to how the lower
compared with running [9–11]. It is therefore more likely
body interacts with the ground upon landing. The body is
for injury to occur during running. The focus for this
modelled as a point mass balanced on a compressible
review was therefore directed at running.
spring while the joints are modelled as torsional springs
Research into the nature of overuse Achilles tendon
witheach‘spring’havingaspecificstiffness,k(seeFig. 1)
injuriesisextensive,yetuncertaintyremainsaroundhowto
identify athletes susceptible to Achilles tendon injury. Our
recent review on Achilles tendon injury risk factors asso-
ciated with running identified two variables, high vertical
forces and high arch, which showed strong evidence for
reducedinjuryrisk.Highpropulsiveforcesandrunningon
stiffer surfaces may also be protective [12]. Only one
biomechanical variable, high braking force, showed clear
evidence for increasing Achilles injury risk. The majority
ofthebiomechanicalriskfactorsexaminedshowedunclear
results,whichmaybeattributedtothemultifactorialnature
of Achilles overuse injuries.
Many risk factors are related to how the athletes’ body
interacts with the environment during gait including Fig.1 Biomechanicalstiffnessmodelsforchangesin(a)verticaland
groundreactionforces,muscleactivitypriortolandingand legstiffness[19],and(b)jointstiffness[18]duringrunning.Vertical
stiffness is calculated from maximum vertical force and centre of
immediately post-ground contact and joint motion
mass(COM)displacement.Legstiffnessiscalculatedfrommaximum
throughout stance. The largely inconclusive results for
vertical force and ‘leg spring’ compression (L). Joint stiffness is
individual risk factor analysis highlight the need for an calculatedfromchangesinjointanglesandmoments
123
StiffnessasaRiskFactorforAchillesTendonInjury
[18, 19]. Despite the simplicity of the model, the risk factors for Achilles tendon injuries and lower
mechanics of gait are efficiently represented. Centre of extremitystiffness.Thefindingswilldirectfurtherresearch
mass displacement is achieved via compressionof the ‘leg into measures for identifying Achilles tendon injury risk.
spring’ whose length is modified via rotation of the joints
(Fig. 1a, b). The rate and extent of joint rotation is con-
trolled by the surrounding muscles, ligaments and tendons 3 Methods
working against the externally applied force. Control of
stiffness is likely to be both centrally mediated from the Cochrane Collaboration review methodology (literature
cortex and possibly central pattern generators as well as search; assessment of study quality; data collection of
through reflex activation [20–22]. study characteristics; analysis and interpretation of results;
Hopping and running tasks are both used for stiffness recommendationsforclinicalpracticeandfurtherresearch)
analysis. The task and biomechanical stiffness model used was used [23].
are largely determined by the constraints of the testing
environmentandequipmentavailable.Thebasicequations 3.1 Search Parameters and Criteria
for estimating stiffness are:
F Databases PubMed, SPORTDiscus, CINAHL and Web of
kvertical ¼ Dmyax; ð1Þ Science to October 2015 were searched for terms linked
with Boolean operators (‘‘AND’’, ‘‘OR’’, ‘‘NOT’’): verti-
F
k ¼ max; ð2Þ cal/leg/joint/ankle/knee/hip stiffness; arch height; braking
leg DL
force;verticalforce;runningdistance;runningexperience;
DM eccentric strength; concentric strength; knee flexion; ankle
k ¼ ; ð3Þ
joint Dh dorsiflexion;ankleeversion;anklecoupling;tibialrotation;
muscle activity; running speed; age; sex. Papers were
whereF isthemaximumverticalforce,Dyisthecentre
max
selected based on title, then abstract and finally text. Rel-
of mass displacement, DL is the change in ‘leg spring’
evantreferencesfromthetextofselectedarticleswerealso
length, DM is the change in joint moment and Dh is the
retrieved and included in the analysis. Papers were exclu-
changeinjointangle.Owingtothebiarticularnatureofthe
ded if their content included the following topics: any
gastrocnemius muscle there is potential for both the knee
movementthatwasnotrunningsuchasverticaldropjump;
and ankle to play a role in Achilles injuries.
tendon stiffness; musculoarticular stiffness; oscillation
There have been few studies investigating the link
stiffness method; passive stiffness; sled testing; change of
betweenstiffnessandAchillestendoninjuries.AsAchilles
direction; stretching; upper body, without including run-
injuries are the result of cumulative damage and are a
ning or hopping stiffness measures. Case reports, reviews,
progressive injury it is likely that a number of risk factors
editorials, letters to the editor and all animal studies were
come together in each individual to result in the injury.
excluded. Papers were included that specifically addressed
Each risk factor by itself may be statistically insignificant.
aspects of training or racing encountered by triathletes,
The authors believe that joint and leg stiffness provide a
such as fatigue and running off the bike.
holistic view of how the lower limb is functioning during
A total of 13,529 papers were identified of which 5762
running. Stiffness therefore could provide a measure that
were duplicates. After selection for inclusion criteria and
was able to pick up risk by taking into account all the
eliminationbasedonexclusioncriteria,57paperswereleft
different risk factors of the individual athlete. The limita-
for inclusion into the final review (Fig. 2).
tions regarding methods used to quantify stiffness, in par-
ticularthecomplexlinkbetweenglobalmeasurementsand
3.2 Assessment of Study Quality for Systematic
local alterations, means that associations with injury may
Review and Data Extraction
be difficult to determine.
Owing to the diversity of study types (between subject
repeated measure, within subject repeated measure and
2 Objective
correlation analysis as reported in Electronic Supplemen-
tary Material Appendix S1), and the known influences on
UsingtheriskfactorsforAchillesinjuriesidentifiedinour
stiffness,anewnine-itemstudyinclusioncriteriascalewas
previous review [12], vertical ground reaction force,
developedbasedonthePEDro[24]andBizziniscales[25]
braking and propulsive force, surface stiffness and arch
(Table 1). Exclusion criteria as well as inclusion criteria
height, the objective of this systematic review was to
were deemed important as this gave better insight into the
determine whether there is a link between running related
characteristics of the groups being studied as the nature of
123
A.V.Lorimer,P.A.Hume
Fig.2 Flowofinformation
throughthedifferentphasesof
thesystematicreview.
kstiffness
the research does not allow blinding and true randomisa-
Table1 Studyqualityscorecriteria
tion. Body weight normalisation of results was important
Number Criteria
when groups were significantly different owing to the
1 Eligibilitycriteriawerespecified(specificallyactivity effect that body weight has on stiffness measures. Where
level) randomisation was not possible such as cross-over with
2 Exclusioncriteriadescribed(specificallyinjurycriteria) only one measurement, or a reason for lack of randomi-
3 Eachgroupcontainedatleasttenparticipants sation was given, the study quality point was awarded.
4 Groupsweresimilaratbaselineforheight,weight,sexand Stiffness changes required two means, effect sizes or cor-
age(nosignificantdifference)orresultswereweight
relations and required confidence intervals or standard
adjusted
deviations to meet these criteria. The quality scores based
5 Randomisationwasemployedwherenecessary
on the paper selection criteria ranged from 4 to 9.
6 Frequencyand/orhorizontalvelocitywerespecified
7 Ameasureofchangeinstiffnessandvariabilityforatleast
3.3 Analysis and Interpretation of Results
onekeyvariablewasgiven
8 Atleastfivelandingsperpersonperconditionwereused
All differences in stiffness between study conditions were
forstiffnessanalysis
convertedintoeffectsizes.Effectsizeswith95 %confidence
9 Statisticalanalysiswasdetailed
limits were calculated from means and standard deviations.
123
StiffnessasaRiskFactorforAchillesTendonInjury
Both between- and within-subject repeated-measure effect Assurfacestiffnessorarchheightwasincreased,riskof
sizes were calculated as the difference between the means Achilles tendon injury was reduced [12]. Low arches and
dividedbythepooledstandarddeviation.Itisacknowledged lowsurfacestiffnessmaybeharmfultotendonhealth[12].
thatthismethodmayoverestimatetheeffectsizeandconfi- Threestudiesinvestigatedchangesinverticalstiffness[34–
denceintervalinwithin-subjectanalysis,owingtothelackof 36], six leg stiffness [34–39], and one knee and ankle
completeindependence;however,thelackofexactpvaluesin stiffnesswithchangingsurfacestiffness[37].Therewasan
the majority of studies prevented the use of alternative increaseinverticalstiffnesswhenrunningacrossasurface
methods[26].Tomaintainconsistency,allresultsweretreated with increasing stiffness at 3.0 m/s [34]. All other results
with the same method regardless of reporting of p values. for vertical stiffness were not clear and showed decreased
Correlations were converted to effect sizes by d ¼pffi2ffir or unchanged stiffness. Of the seven comparisons that
1(cid:2)r2
showed clear results, all but one showed decreased leg
(whered = effectsizeandr = correlationcoefficient)with
stiffness with increasing surface stiffness for both hopping
confidenceintervalscalculatedusingtheFisher’sztransfor-
and running [34, 37, 39]. All results for knee and ankle
mationpriortoeffect-sizeconversion[23].Studycharacter-
stiffness during bipedal hopping were unclear [37]. The
istics and quality scores are reported in Electronic
trend was for decreasing ankle stiffness and increasing
Supplementary Material Appendix S1. Stride rate analysis
knee stiffness as surface stiffness increased. Increasing the
in a variety of running populations ranged from 1.3 to
stiffness of the midsole resulted in small decreases in both
1.7 Hz [27, 28]; therefore, frequency conditions were
kneeandanklestiffness[40].Onlyonestudyhascompared
limited to the range between 1.5 and 2.5 Hz (preferred
archheightandlegandjointstiffness[41].Increasingarch
hopping frequency = *2.2 Hz). Stiffness differences
height was associated with an unclear but moderate
related to the factors previously identified as clearly
increase in leg stiffness and a moderate increase in knee
increasing or decreasing risk of Achilles tendon injuries
stiffness [41].
[12], are presented in Table 2 while all other risk factors
Other risk factors (pace variables, age, sex, footwear,
are presented in Table 3. An effect size of 0.2–0.6 was
muscle activity patterns, intensity and rearfoot angle) did
considered small, 0.6–1.2 moderate, 1.2–2.0 large and
not show distinct association with Achilles tendon injury
greater than 2.0 very large [29].
but could still be involved in the injury process [12]. The
triathlon-specific variable of transitioning from cycling to
4 Results running was also considered for injury risk potential. As
fatigue cannot be discounted from any cycle to run tran-
In our previous review on risk factors for Achilles injuries sition effects, the effects of fatigue was incorporated.
in running athletes, high peak braking force was shown to Results were variable with only increasing muscle activity
increase Achilles tendon injury risk, while high peak and decreasing contact time showing conclusive increased
propulsive and vertical force, increasing surface stiffness joint stiffness (Table 3).Theeffect ofthese riskfactorson
and increasing arch height were protective [12]. Two stiffness are given in Table 3 and the general trend of the
studies investigated braking force and vertical and leg data summarised.
stiffness [30, 31]. Increasing braking force showed a large Velocity, and parameters associated with velocity, were
increase in vertical and leg stiffness when running at pre- measuredforallstiffnessvariables.Anincreaseinvelocity
ferred pace [30]. However, when running at 95 % of was generally associated with moderate to large increases
VO2max(maximumvolumeofoxygenuptake)therewasno in vertical stiffness [30, 33, 42–44]. Leg, knee and ankle
clear effect [31] (Table 2). Increased propulsive force stiffness showed trivial to small increases with increasing
(Fymax), which demonstrated small protective effects for velocity [30, 33, 42, 43, 45]. Increasing contact time
Achilles injuries [12], was associated with moderate to resulted indecreasedvertical[30,33,46],leg [30,33,47–
large increases in both vertical and leg stiffness [30, 31]. 49] and ankle stiffness [45, 50, 51]. Increasing stride rate
Three studies reported the relationship between vertical resulted in increased vertical [30, 32, 33, 43, 52–54], leg
force (Fzmax) and vertical and leg stiffness [30, 32, 33]. [30, 33, 43, 48, 50, 53–56], knee and ankle stiffness [50,
Running at preferred pace showed clear increases in ver- 56]. Stride length however was variable, giving increases
tical andlegstiffness with increasing force [30].Increased [30,33,43],decreases [31,33,49]andnochange[30,43]
verticalforcewithsprintingwasassociatedwithanunclear for both vertical and leg stiffness.
increase in vertical and an increase in leg stiffness [33]. Bipedal hopping at 2.2 and 2.0 Hz resulted in male
Treadmill running at 80 % VO2peak (peak volume of oxy- individuals having moderately larger leg stiffness [57] and
genuptake),however,gaveanincreaseinlegstiffnessand moderatelysmallerlegstiffness[58]comparedwithfemale
decrease in vertical stiffness, both of which had unclear individuals. At 2.5 Hz [58] and preferred hopping fre-
effect sizes [32]. quency [59, 60], the differences were small and both
123
A.V.Lorimer,P.A.Hume
s e m
eindicate Referenc [30] [31] [30] [31] [33] [32] [30] [34] [36] [35] [37] [38] [39] [41] maximu
siz 1 5 5 max
negativeeffect 95%CI -47.56,40.3 -36.77,36.6 -54.54,48.4 Fakingforce,z
A e 2 6 5 br
arity. Ankl ES -3.6 -0.0 -3.0 mum
cl xi
9])areshadedfor 95%CI -117.07,123.24 -95.41,95.55 -132.42,137.80 0.61,0.65 Feforce,maymin
2 v
zero[ Knee ES 3.09 0.07 2.69 0.63 opulsi
ss pr
notcro 2.90 1.70 2.50 5.00 3.04 2.43 6.15 1.28- 2.09- 4.60 4.25 4.87 3.12 11.87- 5.57- 4.93 15.27 3.42- 4.38- 7.01- 1.38 ximum
s(CIdoes 95%CI -0.28, -1.86, -0.52, 0.10, 0.24, -0.21, 1.12, 4.48,- 5.07,- -4.15, -4.03, -3.31, -5.40, 13.86,- 10.33,- 0.02, -19.84, 6.88,- 7.63,- 10.14,- -0.07, Fmaymax-enuptake
earresultmeasure Leg ES 1.07 -0.06 0.81 1.91 1.42 0.95 2.98 2.88- 3.58- 0.23 0.11 0.78 -1.14 12.86- 7.95- 2.47 -2.29 5.15- 6.00- 8.57- 0.65 ectsize,eakoxyg
donriskfactorsonlowerbodystiffnessmeasures.Clefirstconditionstatedresultedinalowerstiffness MovementVertical ES95%CI 1.570.14,3.70Run(preferred) Run(95%VO)2max 1.790.30,4.06Run(preferred) Run(95%VO)2max Sprint(max)0.87-0.24,2.25 TMrun(80%VO)-0.45-1.75,0.702peak 1.850.35,4.18Run(preferred) 2.270.90,3.64Run(3.0m/s) 0.46-1.14,2.07 Run(3.7m/s)-0.56-3.42,2.29 -0.37-2.83,2.10 -1.22-5.05,2.61 Run(5.0m/s)0.04-6.99,7.07 Bihop(2.2Hz) Bihop(2.0Hz) Bihop(2.2Hz) Run(3.4m/s) italics cont.ESeinterval,continuousstiffnesssurface,effVOVOmaximumoxygenuptake,padmill,2max2peak
Table2EffectofthefiveclearAchillestenthatdecreasingthevariableofinterestorth FactorChange FCorrelationymin Correlation FCorrelationymax Correlation FCorrelationzmax Correlation Correlation kSurface21.3–533kN/m Cont.21.3–cont.533kN/m 220–950kN/m 450–950kN/m 75–950kN/m Low–high 30–35,000kN/m 60.9–35,000kN/m 30–60.9kN/m 26.1–50.1kN/m 27–411kN/m(expected) 27–411kN/m(surprise) Cont.27–cont.411kN/m ArchheightLowarch–higharch Allcleareffects(CIsdonotcrosszero)are bihopCIbipedalhopping,95%confidencmaxTMverticalforce,maximumeffort,tre
123
StiffnessasaRiskFactorforAchillesTendonInjury
that ence
dicates Refer [33] [43] [44] [45] [30] [42] [122] [33] [30] [49] [48] [47] [51] [33] [43] [32] [30] [75] [53] [48] [50]
n
i 7 9 1
size 1.49 1.74 2.31 2.13 3.53 4.17 3.65 0.5- 0.7- 1.9- 0.77
ect CI 9, 4, 1, 9, 2, 4, 8, 0, 2, 8, 2,
eff % 1.4 1.7 1.9 1.6 2.5 2.9 3.6 2.8 6.3 0.1 0.5
ve 95 - - - - - - - - - 1-
ati
Aneg Ankle ES 0.00 0.00 0.20 0.22 0.50 0.62 -0.02 1.54- 2.76- 4.69- 0.65
y.
arit 7 2 99 77 7 5 0 6
forcl CI 7,4.1 6,5.4 6,11. 8,11. 5,3.3 6,4.4 5,4.0 8,0.7
haded 95% -4.3 -4.7 -10.9 -10.4 -1.8 -2.7 -3.5 0.2
s
e
ar e 10 33 51 64 76 85 23 52
9]) Kne ES -0. 0. 0. 0. 0. 0. 0. 0.
2
[
crosszero CI 47,1.92 74,2.25 66,35.49 21,54.39 39,58.46 83,42.99 23,1.58 33,3.02 24,3.74 08,2.08 57,2.77 52,0.07 92,0.24- 87,1.72- 37,0.39 72,1.17- 73,7.44 22,2.29 60,2.42 11,1.71 46,0.64 38,2.48 10,6.07 70,5.76 30,3.18 99,7.86 48,0.96
snot 95% -0. -1. -33. -53. -58. -39. -1. -3. -2. -2. -2. -2. 3.- 20.- -5. 5.- -9. -0. -1. -1. 0. 2. 0. -0. -2. -4. 0.
e
o
d 3 8 1 9 4 8 5 5 5 0 0 6 0 0 9 4 4 0 9 4 5 3 9 3 4 3 2
6 1 9 5 0 5 1 1 7 0 1 0 7 6 4 4 1 9 2 2 5 4 0 5 4 4 7
(CI Leg ES 0. 0. 0. 0. 0. 1. 0. -0. 0. 0. 0. -1. 1.- 6.- -2. 3.- -1. 0. 0. 0. 0. 2. 3. 2. 0. 1. 0.
s
arresultmeasure 2.15 5.29 4.17 3.97 8.74 13.12 12.25 0.31 0.30- 4.03 4.94 6.02 4.44 4.12 4.61 12.09 12.16
easures.Cleerstiffness cal 95%CI 0-0.31, 4-0.11, 8-0.55, 30.26, 1-7.32, 1-10.30, 0-10.66, 0-2.15, 94.06,- 80.74, 7-0.23, 31.49, 10.47, 5-2.22, 8-2.06, 55.62, 9-0.78,
ssmlow Verti ES 0.8 1.8 1.2 1.7 0.7 1.4 0.8 -0.8 1.7- 2.0 1.6 3.2 2.0 0.9 1.2 8.8 5.6
ea
n
ctorsonlowerbodystiffnditionstatedresultedin Movement Sprint(max) Sprint(max) Sprint Sprint Run(preferred) Run TMrun Sprint(max) Run(preferred) Run(vVO)2max Run(3.3m/s) Bihop(preferred) Bihop Sprint Sprint(max) Sprint(max) TMrun(80%VO)2peak Run(preferred) Run(78%VO)2max TMrun(2.5m/s) Run(3.3m/s) Bihop
ao
ofAchillestendoninjuryriskfariableofinterestorthefirstc Change Correlation Correlation Correlation100m 70%(7.0m/s)–80%(7.8m/s) 80–90%(8.8m/s) 90–100%(9.7m/s) 70–100% Correlation 2.5–3.5m/s 3.5–4.5m/s 4.5–5.5m/s 3.0–4.0m/s Correlation Correlation Correlation Short-preferred Preferred-long Short-preferred Eld.correlation 70%maxcorrelation 100%maxcorrelation Correlation Correlation Correlation Correlation -8%—preferred Preferred—?8% -26%—preferred Preferred—?30% -30%—preferred Preferred—?30% 1.5–2.1Hz
v
Table3Effectdecreasingthe Factor Velocity Contacttime SR/Hz
123
A.V.Lorimer,P.A.Hume
e
c
n
e
Refer [56] [55] [52] [33] [43] [31] [30] [49] [61] [51] [40] [63] [62] [58] [57] [58] [102] [60] [59] [40] [64] [68] [66] [67] [67] [40] [65]
4.09 1.62 1.53 0.06- 0.24- 1.78 0.46 3.95 35.87 0.34-
CI 48, 95, 53, 96, 69, 37, 08, 8,3 74, 62,
% 2. 0. 1. 2. 0. 0. 0. 1. 5. 0.
95 - - - - - - - -3 -3 -
e 0 4 0 1 7 1 9 7 7 8
nkl S 0.8 0.3 0.0 1.5 0.4 0.7 0.1 1.0 0.0 0.4
A E - - -
11.33 2.75 4.87 4.11 0.10 0.03- 1.84 8.12 8.28 0.20-
CI 23, 38, 60, 24, 10, 97, 55, 6,1 2,1 32,
% 0. 2. 3. 4. 0. 0. 1. 7. 9. 0.
95 -1 - - - - - -1 -1 -
5 9 4 6 0 0 0 6 6 6
e 5 1 6 0 0 5 7 2 4 2
ne S 0. 0. 0. 0. 0. 0. 1. 0. 0. 0.
K E - - - -
6 5 2
26 48 79 54 98 31 0.6 45 07 0.6 79 0.0 36 11 44 77 69 90 52 94
1. 2. 1. 0. 1. 1. - 5. 0. - 0. - 0. 0. 0. 0. 4. 2. 2. 0.
CI 0, 8, 1, 3, 9, 9, 3, 3, 0, 9, 7, 8, 0, 3, 7, 3, 0, 6, 8, 9,
0 3 7 8 9 4 2 0 1 7 5 2 1 2 2 1 3 0 9 9
% 1. 2. 1. 1. 1. 1. 3. 7. 0. 0. 0. 0. 0. 0. 0. 2. 3. 3. 2. 1.
95 - - - 1- - - - - - - - - -
3 3 5 6 0 7 6 9 1 2 8 5 3 6 6 8 0 8 3 3
1 4 7 5 0 0 0 7 0 7 6 1 2 0 3 6 0 0 2 5
Leg ES 1. 2. 1. -0. 0. -0. 4.- -0. -0. 0.- 0. 0.- 0. -0. 0. -0. 4. 0.- 0.- 0.-
1 2 5
8 0 9 0 9 1 1 8 8 2 2
7.2 7.9 0.4 2.9 1.2 2.4 15. 2.6 30. 47. 1.7
CI 8, 5, 9, 4, 3, 8, 3, 6, 9, 5, 5,
4 4 8 2 3 5 6 0 3 4 8
% 5. 5. 1. 1. 2. 0. 3. 4. 0. 5. 2.
95 - - - - - - -1 - -3 -4 -
al
c 0 3 1 9 9 5 4 9 2 0 6
erti S 0.9 1.2 0.6 0.5 0.3 0.7 0.7 0.6 0.2 0.9 0.5
V E - - - -
)x
Movement Bihop Unihop Unihop Sprint(max) Sprint(max) Run(95%VO2ma Run(preferred) Run(vVO)2max Bihop(1.5Hz) Bihop Run(3.3m/s) Run(3.8–4.1m/s) Bihop(2.2Hz) Bihop(2.0Hz) Bihop(2.2Hz) Bihop(2.5Hz) Bihop(preferred) Bihop(preferred) Bihop(preferred) Run(3.3m/s) TMrun(3.6m/s) Run Hop(2.2Hz) Run(3.3m/s) Run(3.3m/s) Run(3.3m/s) TMRun(65%VO)2max
y
ed Change 1.5–2.1Hz(/kg) 1.5–2.2Hz(D) 1.5–2.2Hz(ND) -20%—preferred Preferred—?20% Correlation Correlation Correlation Correlation Correlation Men–boys Young–eld.(50%max) Young–eld.(75%max) Young–eld.(100%max) y16–20–36–60 y\35–50? Young–eld. Female–male Female–male Female–male Female–male Female–male Female–male yFemale35?–male35? Barefoot–350-gshoe Shoe-racingflat(female) Shoe-racingflat(male) Barefoot–shoe Barefoot–shoe(0-mmmidsole) 0mmmid–16-mmmidsole Soft–hardmidsole Minimal–standardshoe
u
n
nti h
3co lengt ear
Table Factor Stride Age Sex Footw
123
StiffnessasaRiskFactorforAchillesTendonInjury
e
c
n
e
Refer [71] [123] [69] [72] [70] [41] [69] [51] [88] [33] [43] [73] [44] [83] [31] [32] [75]
2 1 9
2.2 63 56 58 92 48 97 02 0.7 0.1
- 2. 3. 3. 1. 1. 2. 4. - -
CI 0, 3, 1, 1, 4, 0, 7, 6, 3, 0,
9 6 1 5 3 0 6 2 0 2
% 5. 0. 1. 0. 0. 0. 0. 1. 3. 2.
5 - - - - -
9
e 6 0 3 5 6 0 7 1 1 9
nkl S 4.0 1.0 2.3 1.1 1.0 0.7 1.6 2.4 1.7 1.0
A E - - -
1
2 8 7 2 2
8.9 6.3 10. 1.9 3.6
CI 6, 6, 2, 4, 4,
6 4 4 3 0
% 5. 2. 3. 0. 1.
5 - -
9
3 6 7 6 4
e 6 9 0 0 1
ne S 1. 1. 7. 1. 2.
K E
9 7 0
75 0.2 0.1 74 60 32 76 31 71 95 46 15 98 1.2 92 15 44 96 59 37 79 64 41
1. - - 0. 8. 8. 2. 0. 1. 1. 2. 2. 1. - 1. 5. 5. 3. 5. 2. 0. 0. 1.
CI 2, 8, 1, 0, 3, 7, 8, 7, 9, 7, 8, 5, 8, 5, 8, 1, 8, 0, 8, 1, 1, 6, 1,
5 9 8 0 4 5 9 7 1 3 2 4 5 2 6 7 1 2 0 2 5 1 6
% 1. 1. 1. 3. 8. 6. 0. 1. 0. 0. 1. 1. 1. 2. 5. 5. 3. 5. 6. 3. 2. 1. 1.
5 - - - - - - - - - - - - - - - - - - - -
9
4 6 3 3 8 7 7 5 0 9 9 5 0 3 8 8 3 2 4 2 6 6 0
6 0 9 1 0 8 6 6 9 0 5 3 2 7 8 2 1 6 2 4 8 2 1
Leg ES 1. 1.- 0.- 1.- 0. 0. 0. -0. 0. 1. 0. 0. 0. -1. -1. -0. 1. -0. -0. -0. -0. -0. -0.
25.51 4.32 4.07 3.78 -1.98 9.01 8.18 7.29 12.21 14.34 5.06 0.79 2.09 3.79
CI 7, 8, 8, 3, 0, 3, 1, 6, 3, 9, 0, 1, 2, 3,
6 5 6 6 4 5 6 0 4 1 1 5 6 1
% 4. 3. 3. 3. 7. 5. 9. 8. 4. 7. 5. 2. 2. 4.
95 -2 - - - - -1 - - -1 -1 - - - -
al
c 2 7 0 8 9 6 1 9 1 3 2 9 7 7
erti S 0.4 0.3 0.2 0.0 4.6 3.2 0.7 0.3 1.1 1.4 0.0 0.0 0.2 0.1
V E - - - - - - - - -
)x )x
s) ma ma
Movement Bihop Run(3.4–4.2m/ Bihop Run(3.3m/s) Run(preferred) Run(3.4m/s) Bihop Bihop Run(LT) Sprint(max) Sprint(max) Sprint Sprint Run(VO)2max Run(95%VO2 TMrun(80%VO)2peak Run(78%VO2
ed Change Untrained–endurance Runcorrelation Staticcorrelation Closed–opened 3–4BW 3–6BW Pre–post-weightedsledtrain Gpreact.correlation VLonsetcorrelation Solpreact.correlation Lat.Gpreact.correlation Med.Gpreact.correlation Eld.sol(BR/PR)correlation. Eld.med.G(BR/PR)correlation Eld.lat.G(BR/PR)correlation Eld.TA(BR/PR)correlation Eld.TA/solcoact.correlation CR–5%T2 CR–20%T2 CR–100%T2 2nd–12thsprint 25–375m Sprint1–sprint2 Sprint1–sprint4 1st–2nd100m 1st–4th100m 10–100% 10–100% Pre–post Pre–post
u
n
nti
o
c n
Table3 Factor Trainingstatus RFA Intensity Strength Muscleactivity Transitio Fatigue
123
A.V.Lorimer,P.A.Hume
Reference [76] [78] [65] [49] [84] [85] [86] [80] [81] [74] [77] [87] [82] [30] [60] lat.G.size,lateralpref.Preactivation,VLvastuslateralis,
95%CI ESeffectpreact.e,hopping,
Ankle ES Elderly,propulsivunipedal
Eld.PRhop
%CI ngleg,xercise,unimill,
95 ntkickinningeMtread
Knee 95%CIES -0.01,0.85 -0.03,0.59 -3.69,3.75 -3.31,3.72 -1.99,0.94 -2.72,0.95 -2.38,1.36 -1.83,0.70 -4.55,-2.82 -1.09,0.82 -3.19,3.19 -0.60,2.26 -1.24,0.57 -2.84,2.86 -1.33,0.65 -1.19,0.95 0.11,0.93 -0.42,0.35 -0.49,0.37 -17.43,17.78 -11.28,11.65 RDcontrolrun,dominapostkickingleg,post-ruTATn,tibialisanterior,
Leg ES 0.42 0.28 0.03 0.20 -0.53 -0.89 -0.51 -0.57 -3.68 -0.14 0.00 0.83 -0.33 0.01 -0.34 -0.12 0.52 -0.03 -0.06 0.18 0.18 Cation,ominantsitionru
vdn
al 95%CI 0.94,1.66 2.54,3.11 -5.60,5.63 -5.01,5.63 -2.62,2.42 -25.77,25.08 -10.27,10.53 -5.28,3.94 -6.20,-1.59 -2.33,3.25 -5.07,5.93 -3.39,3.55 -5.16,6.70 -1.49,2.54 -6.48,6.50 -2.12,0.72 -1.71,1.54 -0.11,0.73 2.11,1.35-- 2.08,0.65-- 0.08,0.40 -6.78,6.97 coact.val,CoactiNDmeffort,non-T2striderate,traygenuptake
Vertic ES 1.30 2.82 0.01 0.31 0.10 -0.35 0.13 -0.67 -3.90 0.47 0.43 0.08 0.77 0.52 0.01 -0.70 -0.09 0.31 1.73- 1.36- 0.24 0.16 nceintermaximuSRoleus,peakox
Movement Run(70%VO)2max TMrun(2.8m/s) TMrun(65%VO)2max Run(VO)2max Run(95%VO)2max Run(3.5–3.7m/s) Run(2.9–2.7m/s) Run(3.3m/s) Run(3.9m/s) Run(2.8m/s) TMrun(3.3m/s) Run(3.3m/s) Run(3.6m/s) Run(race) Run(preferred) Bihop(preferred) italic CIdyweight,95%confidemaxmedialgastrocnemius,solrear-to-forefootangle,sVOumoxygenuptake,2peak
Table3continued FactorChange Pre–post Pre–post?7-minmax Fatigue0–2h 0–4h Pre–post-50min Pre–post-exhaustion Pre–post-exhaustion Pre–post-Mtmarathon Pre–postuphillmarathon Pre–post-mountainultra Pre–post-multi-stagerace Pre–post-cyclesprints Pre-post Pre–3hpost Pre–post 1st–4thlap 1stlap–finishchute 200–1000m 200–2000m 200–5000m Pre-postsquats(male) Pre-postsquats(female) Allcleareffects(CIsdonotcrosszero)are bihopBRBWbipedalhopping,braking,boLTmed.G.gastrocnemius,lactatethreshold,preRFApreferred,priortorunningexercise,vVOVOvelocityatVOmaxim2max2max2max,
123