Managing the return to sport of the elitefootballer following semimembranosusreconstruction

Matt Taberner ,1 Fares SHaddad,2,3 Andy Dunn,4,5 AdamNewall,6 Lloyd Parker,1,7

Esteban Betancur,8 Daniel D Cohen 8,9

ABSTRACTHamstring strains are the most common injury in elite footballand typically occur during high-speed running. Despite itsimportant contribution to power production in the late swingphase, injury to the semimembranosus (SM) is less commonthan to the biceps femoris, but may involve the free tendon anddepending on the degree of retraction, warrant surgical repair.Few case reports detail clinical reasoning, supported byobjective data during rehabilitation in elite footballers, andnone have described the return to sport (RTS) processfollowing this type of hamstring injury. In this article, we outlinethe management and RTS of an English Premier League (EPL)footballer who suffered a high-grade SM proximal tendon tearduring training. Due to the degree of retraction of the freetendon, the player underwent surgical reconstruction at therecommendation of an orthopaedic surgeon. Earlyphysiotherapy care, nutritional support, on- and off-pitchinjury-specific reconditioning and global athletic developmentare outlined, alongside strength and power diagnostic andglobal positioning systems data, assessment of pain, playerfeedback and MRI informed clinical reasoning and shareddecision-making during the RTS process. 18 weeks post-surgery the player returned to team training, transferring to anew club 3 weeks later. 2.5 years post RTS, the playerremains free of re-injury playing regularly in the EPL.

CASE SCENARIOHamstring injuries are the most prevalent inelite football and the biceps femoris long head(BFlh) the most frequently injured muscle.1

Injury to the BFlh typically occurs during high-speed running (HSR) as the muscle undergoeshigh strain. Despite its important contributionto force production during the late swing phaseof maximal speed running, injuries to the semi-membranosus (SM) are less frequent, and tendto occur in slow stretch type activities.2 3 Thistype of injury may also involve a degree ofretraction of the proximal free tendon, whichmay warrant surgical intervention.3

In this article, we outline the managementand return to sport (RTS) of an English Pre-mier League (EPL) footballer who suffereda high-grade SM proximal free tendon tear(figure 1). The injury occurred during train-ing as he overstretched stepping over the ball.

Surgical repair was required, and 18 weekspost-injury, the player returned to team train-ing. Two and a half year’s post RTS, he isplaying regularly in the EPL without re-injury.There are few case reports in the literaturedescribing the rehabilitation and RTS of elitefootballers in detail and none following thistype of hamstring injury. We share theplayer’s pre-injury and RTS running loads,strength and power (S&P) diagnostic data,on- and off-pitch physical preparation, andthe clinical reasoning and considerationsinvolved in the decision-making process.

DECISION-MAKING PROCESS LEADING TOSURGERYAs the post-injury MRI revealed a retracted tear(figure 2A and table 1), an orthopaedic sur-geon recommended an operative approachover the conservative option which was deemedto present a greater risk of re-injury, extending

To cite: Taberner M, HaddadFS, Dunn A, et al. Managing thereturn to sport of the elitefootballer followingsemimembranosusreconstruction. BMJ Open Sport& Exercise Medicine 2020;0:e000898. doi:10.1136/bmjsem-2020-000898

► Supplemental material ispublished online only. To viewplease visit the journal online(http://dx.doi.org/10.1136/bmjsem-2020-000898).

Accepted 26 September 2020

© Author(s) (or theiremployer(s)) 2020. Re-usepermitted under CC BY-NC. Nocommercial re-use. See rightsand permissions. Publishedby BMJ.

For numbered affiliations seeend of article.

Correspondence toMatt Taberner;matthewtaberner@btinternet.com

Key points

► Semimembranosus injuries tend to occur duringslow stretch type activities and may involve thefree tendon. Depending upon the upon the degreeof tendon retraction, these injuries may warrantsurgical repair.

► Off-pitch rehabilitation progressively integratedhigh-intensity isometrics, high strain eccentricsand exercises requiring intermuscular coordination— emphasising involved limb loading. Alongsidereconditioning specific to the injury, rehabilitationalso provided a ‘loading opportunity’ to integratejump-landing activities to improve the player’soverall athletic qualities.

► On-pitch rehabilitation followed the ‘control–chaoscontinuum’ considering important factors specific tohamstring injury; positional-specific conditioning,progressive exposure to HSR volume and maximalspeed running under increasingly chaotic conditions.

► Communication and a player-centred shareddecision-making process involving externalhealthcare professionals and a multidisciplinaryteam help to ensure optimal player care during RTS.

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RTS and potentially placing the player’s career in jeopardy.Progressing with a conservative approach would haveincreased the formation of scar tissue and resulted ina loss of tension within the SM. This would be expected tohave profound consequences for an elite footballer, interms of the decreased ability to generate force, powerand run at high-speeds, and potential increased risk ofinjury to other hamstring musculature due to compensa-tory demands. Furthermore, delaying surgery or operatingon a scarred tissue bed would increase the challenge ofrestoring anatomy.4

The procedure was undertaken under general anaes-thesia (prone position). A longitudinal incision is neces-sary to access these tears, allowing tracking into themedial window between the hamstring and adductorcompartments. The SM injury lies next to the sciaticnerve and the tendon tends to tear in a staggered way sothere is one segment still connected to the membraneand muscle distally and one segment connected to thetendon insertion proximally. The two segments are iden-tified, the sciatic nerve and its branches protected. Thetwo tendon ends are re-approximated to the correct levelof tension, assessed by restoring anatomy and held

together with Ethibond non-dissolving sutures whichhold in situ long enough for the tendon to heal. Theseare reinforced with Vicryl dissolvable sutures to regain theappropriate tendon length (restore pre-injury length)and to provide tensile strength. The repair is then testedby manual pressure and by applying stretch to the ham-string musculature.

Figure 1 Overview of the return to sport (RTS) of an elite male football player following semimembranosus free tendonreconstruction. Early rehabilitation is divided into two phases: physiotherapy care (Weeks 1–7) and transition into gym-basedphysical preparation (Weeks 8–12) including isometrics (ISO), dynamic strength (DYN) and jump-landing preparation (J-L Prep)and progression from stationary bike to anti-gravity treadmill running (A-GR) (Alter-G, Fremont, CA, USA). Return to participationphase (Weeks 13–17); on-pitch sports-specific reconditioning using the ‘control–chaos continuum’ (weeks displayed on-pitch)plus progression (+) of gym-based physical preparation; ISO+, DYN+ and J-L Prep+. RTS decision=return to team training (Weeks18–20; return to train) and continued progressive optimal loading with reduced volume (sets) of ISO+, DYN+ and J-L Prep+. Arrowsindicate timepoints of isometric posterior chain (IPC), eccentric knee flexor (ENF) and countermovement jump (CMJ) assessments.Data from these strength and power diagnostic tests, quantifying neuromuscular deficits relative to his healthy preseason (PS)values, and his response to on- and off-pitch reconditioning, informed exercise and phase progression decisions.

Nutritional considerations following muscle-tendon injury

Nutritional support had two principal aims► to minimise muscle atrophy by maintaining caloric intake,5 taking

creatine (5g) and 3g omega-3 poly-unsaturated fatty acidsupplements (750 mg docosahexaenoic acid, 1500 mgeicosapentaenoic acid)6 and to promote maximal muscle proteinsynthesis by consuming approximately 35 g every 3 hours (5/day) toachieve a protein intake of ~2 g/kg/BM (170 g).6 Daily energyintake, monitored by 24-hour dietary recall and analysed usinga nutritional software package (Nutritics, v5, Ireland), wasestimated to be ~3000 kcal.

► to promote tendon healing. Beginning at 8 weeks post-surgery, an hourbefore activity the player consumed a collagen (20 g) and vitaminC (80 mg) supplement shown to be beneficial for tendon remodelling.7

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MECHANICAL LOADING AND RTSAnMRI 7 weeks post-surgery, following early post-surgicalphysiotherapy management, showed a good healingresponse (table 1; figures 1 and 2B). Reconditioningthen began under sports science supervision, with dailycommunication including pain response (numerical rat-ing scale; NRS) and periodic checks of the player with theclub physiotherapist (table 1). Submaximal isometrics(at 60–90° knee flexion) were introduced in Week 7and a week later the player performed his first post-injury unilateral isometric posterior chain (IPC) test(figure 3).8 9The IPC test was used to quantify the players’ability (and willingness) to produce maximal force (IPCpeak force', IPC-PF) and early rate of force development(RFD) (force at 100 ms).10 Week 8 interlimb asymmetry(ILA) in IPC-PF was 13% and in force at 100 ms was 7%.While the force at 100 ms ILA was low relative to that ofIPC-PF, this should be considered in the context of thesubstantially larger magnitude declines in force at100 ms than peak force on both limbs (figure 4). Thesedata highlight both the importance of evaluating RFD-related variables following injury and of having healthybenchmark values to reduce the dependence on %ILAas a marker of status and progress.11 12

Exercise selection and programming was based on theoptimal loading concept — to maximise physiologicaladaptation of the involved structures.13 Isometrics werethe predominant mode of strength training during initialprogramming, with the conceptual aims of increasingtendon stiffness and enhancing maximal force

development.14 15 Programming began with unilateralshort-lever overcoming isometrics at 90° hip and kneeflexion (figure 5; single-leg (SL) heel drives — kneedominant; online supplemental video 1) to bias medialhamstring recruitment.9 While this exercise remainedkey prior to gym-based rehabilitation sessions to‘prime' the injury site, progression involved integratinglong-lever yielding isometric variations such as double-leg isometric hip extension, followed by its SL deriva-tive — hip dominant, with knee involvement as the ham-string is elongated (figure 5).16We used >80%ofmaximalvoluntary contraction — the threshold to stimulate thedevelopment of mechanical and material tendonproperties17 and programmed in clusters (3–5×~3–5 s iso-holds), to develop maximal strength, RFD and strength-endurance.15 18 19 We delayed integrating high straineccentric exercises in the initial 2 weeks of reconditioningto avoid excessive mechanical strain on the healingstructures.20 Furthermore, post-injury inhibition isreported during bilateral eccentric loading, potentiallycompromising adaptations,21 whereas maximal iso-metrics elicit higher voluntary muscle activation andlower inhibition.22

With no pain reported (<2/10 NRS) following earlyisometric loading, we added dynamic strength exercises,coaching ‘intent’23 to move as explosively as possible todevelop power, with the conceptual goals of promotingcollagen synthesis, fibre alignment and improving ten-don-tensile strength.24–26 We first introduced the heelelevated hip thrust (hip dominant, with the hamstrings

Figure 2 MRI throughout the return to sport process. Green arrows indicated key prognostic features. (A) 24 hours post-injury: (1)semimembranosus (SM) free tendon laxity and muscle retraction, (2) longitudinal split tearing at SM tendon origin. (B) 7 weekspost-surgery: (1) normal SM tendon/myotendinous junction tension, (2) maturing granulation tissue in SM tendon repair site. (C) 11weeks post-surgery: (1) segmental tendon thickening and restoration of tension, (2) intratendinousmaturing fibrous scar tissue. (D)17 weeks post-surgery: (1) continued maturation of scar tissue throughout the site of surgical repair of the free proximal extramuscular portion of the SM tendon, (2) long segment of tendon repair shows relatively uniform low signal intensity scarring andmaintains normal tension throughout the extra muscular portion and the proximal intramuscular portions of the tendon.

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Taberner M, et al. BMJ Open Sp Ex Med 2020;0:e000898. doi:10.1136/bmjsem-2020-000898 3

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ugust 24, 2021 by guest. Protected by

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MJ O

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nloaded from

Tab

le1

Injury

details,surgica

linterve

ntion,

cons

ultant

summaries,phy

siothe

rapyca

rean

dMRId

etailsthroug

hout

reha

bilitatio

nfollo

wingse

mim

embrano

susreco

nstruc

tion

Injury

14Aug

ust20

17

Surgical

interven

tion

19Aug

ust20

17(5

day

spost-injury)

Early

phy

siotherap

yca

re(W

eeks

1–7)

Rep

eatMRIa

ndco

nsultant

chec

k-up

(7wee

kspost-o

p)

Phy

siotherap

yca

re→

sportssc

ienc

e(W

eeks

7–11

)

Rep

eatMRIa

ndreha

bilitationup

date

(11wee

kspost-o

p)

Rep

eatMRIa

ndco

nsultant

chec

k-up

(17wee

kspost-o

p)

Playe

rfelta‘sha

rp’ac

ute

painin

pos

terio

rthigh

(proximal)a

fter

step

ping

over

theballa

ndstretching

.Playe

rimmed

iatelystop

ped

andwith

drewfrom

thepitc

h—icean

dco

mpress

ion

applied(pha

se1;

rest,ice

,co

mpress

ionan

delev

ation

(RICE).

MRIp

erform

ed24

hours

pos

t-injury.

MRIs

ummary(A):ac

ute

high

-gradepartia

ltea

ring

extend

ingthroug

hout

along

cran

ioca

udal

dim

ension

invo

lvingtheproximal

free

extramus

cularportio

nof

these

mim

embrano

sus(SM)

tend

on,w

ithlong

itudinal

splittearingat

theoriginan

dpartia

ltrans

versefib

redisruptio

nof

the

mem

brano

usportio

nof

the

tend

on,w

hich

compris

esap

proximately50

%disruptio

nof

thetend

onfib

resco

ntinuing

into

along

segm

ento

fminor

partia

ltearingof

themyo

tend

inou

sjunc

tion(M

TJ)rep

rese

nting

agrad

e3C

injury.

Ass

ociatedlaxity

ofthe

pelvictend

inou

sportio

nof

thefree

tend

onan

dmild

distalretractionof

the

mus

clebellyaread

verse

imag

ingprogn

ostic

features

.Exten

tofinjuryex

plained

toplaye

rbymed

ical

team

;co

nsultw

ithan

orthop

aedic

surgeo

n—su

rgical

repair

advise

d.

Playe

rund

erwen

tsurge

ryat

thePrin

cess

Grace

Hos

pita

l,Lo

ndon

.Bothse

gmen

tsof

the

horsetail(ruptureden

dof

thetend

on)w

eremob

ilise

dan

dhe

ldwith

No.

5Ethibon

d.F

ourse

tsof

Kes

sler

sutureswereus

edto

reco

nstitutean

dbrin

gbac

kthetens

ions

tocrea

teatubular

tend

onproximally.

Themem

brane

was

recrea

tedwith

No.

5Ethibon

dan

dthen

with

1Vicryltoco

verthesu

tures.

Astrong

repairob

tained

andtested

with

thekn

eebac

kin

extens

ion,

thorou

ghwas

hout

perform

ed.

Thene

urov

ascu

lar

structures

werese

enclea

rlyan

dprotected

—intact.

Closu

rewas

affected

inlaye

rsus

ing1Vicryl,2-0

Vicrylfollowed

by3-0

Mon

ocryltosk

in.

Operationdisch

arge

plan:

Tend

onin

a‘shred

ded

’state—

~8wee

kshe

aling

beforeprogres

sing

tostreng

then

ingprogram

me.

Pos

t-ch

eck-up

:6–8wee

kspos

t-op

forclinical

asse

ssmen

tand

obtain

updated

MRI.

Mob

ilise

NWBwith

crutch

es,b

race

at60

–12

0°~4wee

ks+grad

ualw

ean-

off.

Asp

irin+

TEDan

ti-em

bolism

stoc

king

sforVTE

prophy

laxis.

Wou

ndca

re(clean

ing/fres

hdressings

)Sciatic

nervemob

ilisa

tion

Minim

iseatrophy

:co

mbinationof

isom

etric

knee

extens

ion+

NMES

(atrop

hyse

tting)

(60°→90

°)progres

sing

tosu

pported

fund

amen

talm

ovem

ent

patternssu

chas

squa

t(→

ROM),isolated

hipab

/ad

duc

tor+an

klefle

xor/

extens

orstreng

then

ing.

Isolated

hamstrin

gco

ntractionon

invo

lved

limbav

oided

.Hyd

rotherap

y;walking

insh

allow

end.

Softtissu

e;sc

armob

ilisa

tion.

MRIs

ummary(B):Goo

dpos

t-op

features

follo

wing

along

segm

ento

fsurgica

lrepairof

theproximal

extra

mus

cularSM

tend

onan

dproximalregion

ofMTJ

.The

majority

ofthetend

onrepair

show

smaturelow

sign

alfib

rous

tissu

ewith

asm

aller

volumeof

maturingfib

rous

tissu

e.Signific

antly

,the

reis

good

restorationof

the

norm

altens

ionof

the

tend

onrepairsite

aswella

stheintram

uscu

lartend

on.

Thereareno

complicated

features

orco

ncerning

mus

cleatrophicch

ange

.Con

sulta

ntsu

mmary:

satis

factoryprogres

s.Slig

htne

ural

tens

ion

apparen

tbut

notune

xpec

ted,sca

ralittle

distally

thicke

ned→

progres

sso

fttis

sue.

Goo

dhip+kn

eemob

ility/

ableto

gene

rate

reas

onab

leha

mstrin

gco

ntraction

+mus

clebulk‘fa

rbetter’

than

pee

rsat

thisstag

e.MRIs

howsgo

odhe

aling

resp

onse

alon

gsidego

odtens

ionin

theintram

uscu

lar

tend

on+distalm

uscle.

Plan:

progres

sto

S&C

program

me→

football-

spec

ificac

tivity

.Nb.

Objectivestreng

thtesting

prio

rto

RTS

.

Pha

se2:

restorepain-free

rang

eof

motion,

FWB,

integrateprogres

sive

optim

alload

ing.

(criterion:

<2/10

NRS,<

5%ILASLR

/PKE)

Con

tinue

sciatic

nerve

mob

ilisa

tion+

softtis

sue;

scar

mob

ilisa

tion.

Inco

rporatemea

suremen

tsof

SLR

+PKE.

AtW

eek9:

SLR

:87°

each

side

PKE(gen

tle):69

°ea

chside.

Beg

inisolated

hamstrin

gco

ntraction;

includ

ing

progres

sion

ofisom

etric

s(sho

rt→

long

leve

r)—

combinationof

overco

ming/yielding

derivatives

,progres

sintens

ity(%

MVC)a

ndvo

lumetargetinginvo

lved

limb.

Beg

intran

sitio

nto

stationa

rybike(con

centric

actio

n;sh

ort-rang

e).

Gradua

llyintrod

uce

exercise

selection

inco

rporatingsimultane

ous

hipan

dkn

eeex

tens

ion

(interm

uscu

larco

-ordination).

Introd

ucerunn

ing

mec

hanics

(startingwith

walking

derivatives

alon

gsideus

eof

aeroflo

orto

↓im

pac

tforce

s/’elastic’

dem

andwhe

nintrod

ucing

dyn

amic

mov

emen

tsthat

is,A

-skips).

Asses

sIPCstreng

th/R

FD(IP

Cat

90°:biasmed

ial

hamstrin

grecruitm

ent—

startin

gat

Wee

k8,

evalua

tedwee

kly

throug

hout

theRTS

proce

ss.

MRIs

ummary(C):go

odpos

t-op

appea

ranc

esfollo

wingsu

rgical

repairof

theproximal

extramus

cular

SM

tend

onan

dproximal

extent

oftheintram

uscu

lar

portio

nof

thetend

on.

Interval

maturationof

intraten

dinou

smaturing

fibrous

scar

tissu

eisno

ted.

Res

toratio

nof

theno

rmal

tens

ionof

thetend

onan

dmus

clebellyareag

ain

noted,w

ithno

conc

erning

mus

clevo

lumereduc

tionor

MTJ

fattyinfiltration.

Reh

abilitatio

nplanup

date

follo

wingMRI:

Con

tinue

sciatic

nerve

mob

ilisa

tion+

softtis

sue;

scar

mob

ilisa

tion.

Initiatean

tigravity

runn

ing

whe

nsu

pportedby

objectivemea

sures/playe

rco

nfiden

ce(criterion:

<10

%PF%ILA,fullp

ain-free

ROM

<5%

%ILA),MRIp

ositive

healingresp

onse

,playe

rpain-free

<2/10

NRS).

Asses

sENFstreng

thbi-

wee

klyfollo

wingreturn

toon

-pitc

hrunn

ing.

Asses

sCMJperform

ance

compared

topre-injurydata

duringon

-pitc

hreco

ndition

ing.

Pha

se3:

progres

sop

timal

load

ing(S&C)+tran

sitio

nto

on-pitc

hsp

ort-sp

ecific

reco

ndition

ingus

ingthe

‘con

trol–ch

aosco

ntinuu

m’

(pre-injurydata).

(criterion:

<10

%IPC-P

F%

ILA,<

15%

IPC-F

at10

0ms

%ILA,E

NF<15

%ILAplus

tren

dsin

relatio

nto

pre-

injury

data,

pain-free

(<2/10

NRS)o

nan

ti-grav

itytrea

dmillrunn

ingat

90%

BW).

MRIs

ummary(D):

Con

tinue

dmaturationof

fibrous

scar

tissu

ethroug

hout

thelong

segm

ento

frep

airinvo

lving

theex

tramus

cularportio

nof

therig

htSM

tend

on.T

his

refle

ctsun

complicated

pos

t-op

healingwith

good

prese

rvationof

tend

ontens

ionproximal

toan

dwith

intheSM

mus

clebelly.

Mild

residua

lrem

odellin

grelatedmus

cleoe

dem

aat

proximal

extent

ofMTJ

and

mild

perite

ndinou

soe

dem

a,bothof

which

areex

pec

ted

pos

toperativefin

dings

Con

sulta

ntsu

mmary:

Exc

ellent

progres

s.Sca

rlong

but

wellh

ealed;

thisou

tcom

eex

pec

tedan

dex

plained

toplaye

rprio

rto

surgerydue

toex

tent

over

long

tend

inou

sportio

nof

thestag

geredSM

injury.

Mus

clemas

s‘rea

sona

ble’

relativ

eto

visu

alinsp

ectio

nof

theco

ntralaterallim

b.

None

uraltens

ionno

ted/SM

shap

esimilaro

nbothsides

.No'red

flags

'displaye

d.

Planto

reintegratein

team

training

(pha

se4)

with

grad

ualp

rogres

sion

ofhigh

load

san

dhigh

-spee

dac

tivity

while

mon

itorin

gfor

anysymptomsof

tired

ness/

neural

features

(criterion:

<10

%IPC-P

F/F

at10

0ms%ILA,<

10%ENF

%ILAplustren

dsin

relatio

nto

preinjury

data,

GPS

training

load

data(pre-

injury),playe

rpainfree

(<2/

10NRS,p

ositive

playe

rfeed

bac

k,su

rgeo

ndisch

arge

,MRIh

ealin

gstatus

).

MRIs

cans

aresh

ownin

figure1.

BW,b

odyw

eigh

t;CMJ,

coun

term

ovem

entjum

p;~

,Circ

a;↓,Dec

reas

e;ENF,

ecce

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acting isometrically to resist knee extension) and the splitsquat (hip and knee hybrid), subsequently progressedwith external load, and increasing exercise complexityto provide additional challenges to the neuromuscularsystem (figure 5).13 A positive response to these explo-sively performed dynamic hip dominant exercises along-side progressive high-intensity isometrics may beapparent in the IPC response 2 weeks (Week 11) later.IPC force at 100 ms showed large increases in both limbs,although greater on the non-involved side, whileimprovements in IPC-PF were smaller but favoured theinvolved limb. High strain eccentrics were now intro-duced, and to emphasise bi-articular loading and medialhamstring recruitment, we selected the sliding leg curl(SLC),27 later progressed to the SL derivative to increaseinvolved limb overload (online supplemental video 2).28

Slow-stretch shortening cycle (SSC) jump-landing activ-ities were now added, to enhance the global athleticqualities of lower-limb stiffness, neuromuscular controland power.29

PROGRESSING TO ON-PITCH REHABILITATIONAt 12 weeks post-surgery, with 10% ILA in IPC-PF andfollow-up MRI showing further positive healingresponse (table 1; figures 2C and 4), the playerinitiated 70% bodyweight anti-gravity treadmill run-ning (AG-R), progressing to 90% bodyweight (com-pleting three sessions during Week 12; 70%, 80%and 90% bodyweight) (online supplemental video 3).Prior to each AG-R session, the player performeda series of running mechanic drills including A-skipsand straight-leg bounds to replicate the co-ordinationdemands and proximal-distal energy sequencing asso-ciated with running (figure 5).30 These drills were alsoimplemented within on-pitch warm-ups alongsidedrills to develop acceleration and deceleration quali-ties. At Week 12, IPC-PF ILA was <10%, IPC force at100ms ILA was 14%, and to further inform clinicalreasoning and decision-making at 13 weeks, we alsoassessed ENF strength, the player showing 11% ILA aswell as ENF force substantially above threshold pro-spectively associated with elevated hamstring injuryrisk (figure 4).31 We considered that these data pro-vided evidence to support our clinical judgement thatthe level of risk tolerance was above the level of riskexposure and did not warrant a delay in initiating thehigh control phase of the ‘control–chaoscontinuum’.32 The goal of this phase was to exposethe player to submaximal running speeds (<60% pre-injury maximal speed) monitored using global posi-tioning systems, promoting neuromuscular recoveryin preparation for HSR33 and to build player confi-dence in his return to on-pitch activities. The similarimprovements in IPC-PF and IPC force at 100 ms inthe involved limb between Weeks 13 and 14 (figure 4)suggested a positive response to the initial exposure tothe return to running phase and lack of load involvedlimb avoidance in on-pitch activities. Consequently, inWeek 14, we progressed to a low dose of ‘controlled’HSR (within-session 0.30 gameload HSR) alongsidethe introduction of directional change load and tech-nical skill integration (figures 4 and 6). Prior to begin-ning Week 3 of on-pitch reconditioning (Week 15post-surgery), IPC %ILAs (in PF and force at 100ms) were <10% and involved limb IPC-PF and ENFstrength increases of ~15% since Week 13 (figure 3).This gave us confidence in implementinga progressive increment in ‘controlled’ HSR volumethrough aerobic power conditioning (online supplemental video 4) alongside more chaotic activities —

phase-specific pass and move, and positional accelera-tion drills, in the transition to football-specific weeklyperiodisation.32 Off-pitch conditioning progressed(online supplemental videos 5 and 6), increasingmovement velocity emphasis (online supplementalvideos 7 and 8) (figure 5). Additionally, due to thestretch mechanism of the injury in which hip flexioncombined with an inability to control knee extension,we considered the barbell split squat with forward lean

Figure 3 Isometric posterior chain (IPC) test performedusing a portable force platform at 1000 Hz (PS-2141,Pasco, Roseville, CA, USA) with proprietary software(ForceDecks, Vald Performance, Brisbane, Australia). Testperformed with the player lying supine position, the heel ofthe testing limb placed on the force platform resting ona firm plinth with the testing angle set at 90° hip and kneeflexion using a goniometer (Physio Parts, Twickenham, UK)and the non-testing limb relaxed and fully extended. Theplayer was instructed to push the heel of the testing limbinto the force platform exerting as much force as fast aspossible while keeping the buttocks, hips and head on themat and hands crossed on chest. External pressure wasapplied to the non-tested pelvis/hip to prevent hipextension. The player was familiar with the test, butstandardised instructions were given before theassessment, a verbal command of ‘3, 2, 1 GO’ countdownbefore the initiation of a maximal effort contraction whichwas held for 3 s during which consistent verbalencouragement was given ‘PUSH, PUSH, PUSH, RELAX’.Three maximal voluntary contractions were performed with10 s rest between repetitions.

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a key exercise (online supplemental video 9),34 pro-gressed using external load and increasing exercise com-plexity (figure 4). Accommodating resistance was alsoadded to the SL eccentric SLC to increase the speedand strain rate of eccentric loading7 25 while fast SSCplyometric activities were also integrated into the player'sprogramming (online supplemental video 10) (figure 5).We took advantage of this period to integrate condition-ing aimed at developing the capacity to rapidly decele-rate the centre of mass and follow with rapid increasesin concentric force, power,32 explosive and reactive qua-lities important to the player’s playing characteristics.Our S&P diagnostic criterion for progression to the

moderate chaos phase29 was an IPC-PF and IPC force at100 ms ILA <10% and stable outputs (lack of regression)in response to the control to chaos phase (figure 4).The transition to the moderate and high chaos phases isimportant as it exposes the player to substantiallyhigher cumulative weekly HSR, and subsequently pro-gressing to HSR loads reflecting game output, progres-sively higher maximal speed exposure, alongsidepositional requirements and technical skill components(figures 4 and 6; online supplemental videos 11

and 12).10 32 Pre-injury running load and HSR volumesused to plan running load targets were based on playeroutputs under the previous manager’s regime. However,we anticipated higher team training loads under the newregime and therefore aimed to return the player to hismaximum cumulative training HSR volume to adequatelyprepare the player for these demands (figure 6). As anattacking midfielder, it was important to include additionalshooting practice in themoderate and high chaos phases tomitigate injury risk associated with inadequate exposure toball-striking (online supplemental video 13).35 Based ona combination of objective injury-relevant S&P and trainingload data (figures 4 and 6),MRI results highlighting healingand maturation (figure 2D), the surgeons' positive opi-nion (table 1), and positive feedback/lack of painreported by the player, we concluded that the players’level of risk tolerance was above estimation of re-injuryrisk, and 18 weeks post-surgery, the player resumedteam training. Furthermore, comparing the player’scountermovement jump profile to that of pre-injurysuggested a positive response to the off- and on-pitchloading (figure 7). Notably, at Week 17 despite mod-est deficits in jump height (5%) and peak power

Figure 5 Optimal loading approach following semimembranosus free tendon reconstruction during the earlyrehabilitation phase onwards; gym-based physical preparation (Weeks 8–20). Running mechanics prior to anti-gravitytreadmill running and implemented during on-pitch rehabilitation warm-ups. Dark grey=exercise, Light grey=exercisederivative. Strength (strain/stress) and (intermuscular emphasis)=dynamic strength training. w/=with, ↑=increase,↓=decrease, ~=circa, > progression/onto. DB, dumbbell; early, early-stage; end, end-stage; GCT, ground contact-time;mid, mid-stage; Nb., note; reps=repetitions; RFD, rate of force development; ROM, range of motion; S-E, strength-endurance.; SL, single-leg.

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(7%), relative to pre-injury, suggestive of performancedecline secondary to the injury/deconditioning, therewere substantial improvements in strategy/kinetic vari-ables such as eccentric deceleration RFD (20%), con-centric impulse-100 (8%) and lower limb stiffness(13%), indicative of improved SSC ability.11 36 Impor-tantly, at this time point, the player had achieved 97% ofpre-injury maximal speed (figures 4 and 6), without fullrecovery of aspects of neuromuscular performance, andseveral weeks remained before expected return to com-petition to further recover these.In the first week following return to team training

(online supplemental video 14), within-session HSRincreased (a 0.12 gameload increase from previousmax rehabilitation session) while cumulative HSR waswithin his range of chronic weekly volume and otherrunning load markers monitored across the playingsquad (figure 6). Importantly, the player communicatedthat he felt the demands of team training were below

that of rehabilitation (figure 6), suggesting he was ade-quately prepared to cope with a return. Within 2 weeksof his RTS, the player was the subject of a bid fromanother EPL team competing within the UEFA Cham-pions League. Twenty weeks post-surgery and following11 team training sessions, he passed a medical anda transfer was agreed.

SUMMARYFollowing surgery and early care management, on- andoff-pitch loading stimuli were progressively integratedwith global positioning systems and S&P diagnosticsused to quantify running load and monitor player neuro-muscular status, respectively. This objective data, in con-junction with clinical experience from several sourcesand player feedback, informed decisions on phase andloading progression to raise the level of risk tolerance andultimately facilitate a successful outcome for club andplayer.

Figure 6 Return to chronic running loads following semimembranosus free tendon reconstruction using the ‘control–chaoscontinuum’ as a framework for return to sport. Tables show the player’s pre-injury ‘gameload’ running load metrics from season2016/2017. Total distance (TD), high-speed running (HSR)=>5.5ms-1, explosive distance (Exp-D)=accelerating/decelerating from2ms to 4ms-1 <1 s, highmetabolic load distance=distance above 25 w•kg-1; HSR plus Exp-D). Gold box are absolute values. Lightblue and dark blue boxes show relative (multiples of) gameload (ie, 2×=2 games worth) and absolute, mean and max training andconcurrent (training plus game), respectively.Weekly absolute (left y-axis) and relative (right y-axis) TD, high metabolic load distance, HSR and Exp-D are shown foreach week of on-pitch rehabilitation in graphs. Session rate of perceived exertion (session-RPE) (y-axis=arbitrary units)shows weekly accumulated session-RPE (training session duration (min)×RPE). % max speed=(maximum speedachieved in session/player’s pre-injury maximal speed (8.95 ms-1)×100). Control–chaos continuum: Control; highinfluence on behaviour/actions/movement—controlled situations. Chaos; behaviour/actions/movement, unpredictable/random/reactive—chaotic situations. Green=high control, pale green=moderate control, yellow=control to chaos,orange=moderate chaos, red=high chaos and grey=return to team training (RTT). Global positioning systems;augmented 10 Hz Apex (StatSports, Belfast, UK).

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Author affiliations1School of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK2University College London Hospitals NHS Foundation Trust, London, UK3Institute of Sport, Exercise and Health, London, UK4Royal Liverpool and Broadgreen University Hospitals NHS Trust, Liverpool, UK5The OrthTeam, Spire Healthcare Ltd, Manchester, UK6Medical Department, Everton Football Club, Liverpool, UK7Nutrition Department, Everton Football Club, Liverpool, UK8Sports Science Center (CCD), Colombian Ministry of Sport (Mindeporte), Colombia9Masira Research Institute, Universidad de Santander, Bucaramanga, Colombia

Twitter Matt Taberner @MattTaberner, Lloyd Parker @parkernutrition and Danielcohen @daniecohen1971.

Contributors FSH surgically operated on the player, AD provided MRI reports, ANprovided physiotherapy care, LP provided nutritional support, MT led on- and off-pitchphysical preparation, planned and wrote the manuscript, DC provided assistance writingthe manuscript and feedback. MT, DC and EB provided an analysis of S&P diagnostics.

Funding This research received no specific grant from my funding agency in thepublic, commercial or not-for-profit sectors.

Competing interests None declared.

Patient consent for publication Obtained (BMJ consent form).

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has notbeen vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of theauthor(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibilityarising from any reliance placed on the content. Where the content includes anytranslated material, BMJ does not warrant the accuracy and reliability of thetranslations (including but not limited to local regulations, clinical guidelines, ter-minology, drug names and drug dosages), and is not responsible for any error and/oromissions arising from translation and adaptation or otherwise.

Open access This is an open access article distributed in accordance with theCreative Commons Attribution Non Commercial (CC BY-NC 4.0) license, whichpermits others to distribute, remix, adapt, build upon this work non-commercially,and license their derivative works on different terms, provided the original work isproperly cited, appropriate credit is given, any changes made indicated, and the useis non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

ORCID iDsMatt Taberner http://orcid.org/0000-0003-3465-833XDaniel D Cohen http://orcid.org/0000-0002-0899-4623

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