The_Increasing_Role_of_the_Hip_Extensor.7

The Increasing Role of the Hip Extensor Musculature With Heavier Compound Lower-Body Movements and More Explosive Sport Actions

Chris Beardsley,MA(Hons)1and Bret Contreras,BSc,CSCS2

1Strength and Conditioning Research Limited,Loughborough,Leicestershire,United Kingdom;and2School of Sport and Recreation,Auckland University of Technology,Auckland,New Zealand

A B S T R A C T

HIP EXTENSION MOMENTS INCREASE TO A MUCH GREATER DEGREE THAN KNEE EXTENSION MOMENTS WITH INCREASING LOADS DURING THE SQUAT,LUNGE, AND DEADLIFT EXERCISES AND WITH INCREASING RUNNING SPEEDS,JUMP HEIGHTS,AND LAT-ERAL AGILITY MANEUVERS.THERE-FORE,HIP EXTENSION TRAINING SHOULD BE PRIORITIZED IN ATH-LETIC CONDITIONING BY(A)USING HIP-DOMINANT EXERCISES IN THE ATHLETE’S PROGRAM,(B)EMPHA-SIZING HEAVIER LOADS DURING COMPOUND LOWER-BODY RESIS-TANCE EXERCISES AS THE ATHLETE MATURES,AND(C)INCORPORATING LOADS THAT MAXIMIZE THE HIP EXTENSION MOMENT DURING EXPLOSIVE LOWER-BODY TRAINING. INTRODUCTION

I t is generally assumed that sport ac-

tions and resistance-training exercises always require the same relative contribution of the hip and knee muscles,

irrespective of loading or speed.How-

ever,the proportions of joint moments

actually alter in an exercise or sport

action depending on the load or speed

of the movement.In this context,joint

moments are the product of muscular

force and moment arm length.Greater

muscular force of the involved muscula-

ture therefore leads to greater joint mo-

ments,so long as moment arm lengths

remain unaltered.Recent research indi-

cates that a squat or deadlift with

a heavier load is likely to require a differ-

ent proportional involvement(i.e.,ratio)

of the hip and knee extensor muscles.

Some authors have used these ratios

to categorize compound lower-body

movements as knee-dominant(if the

hip-to-knee extension moment is less

than1)or hip-dominant(if the hip-to-

knee extension moment is greater than

1)(10).The ratio of hip-to-knee exten-

sor moments increases with increasing

load during squats(2),lunges(10),dead-

lifts(14),and to a lesser degree,hex-bar

deadlifts(14).In these resistance-

training exercises,this represents an

increase in proportional hip involve-

ment with increasing load.Additionally,

the ratio of hip-to-knee extensor mo-

ments increases with increasing speed

in running(11)and with increasing

jump height in jumping(8).In jumping

and running,this represents not only an

increase in proportional hip involve-

ment with increasing load but also a shift

from knee-dominance at lower intensi-

ties to hip-dominance at higher intensi-

ties.These?ndings emphasize the

critical role of the hip extensors in ath-

letic activities and provide important

information regarding the training of

the hips for optimal performance.

HOW DO HIP EXTENSION

MOMENTS CHANGE WITH

INCREASING SQUAT LOAD?

Recent research indicates that hip

extension moments increase

with

CopyrightóNational Strength and Conditioning Association Strength and Conditioning Journal|https://www.wendangku.net/doc/4e3853137.html,49

increasing load to a greater extent than knee extension moments during the squat.Bryanton et al.(2)investigated the joint moments during the concentric phase of a squat performed by resistance-trained women at varying depths and different percentages of 1repetition max-imum (1RM)(i.e.,loading)(T able 1).The researchers found that hip extension moments increased signi?cantly with increased loading.However,knee exten-sion moments remained fairly constant.This means that the ratio of hip-to-knee extension moments increases with increasing load,making the hips progres-sively more important to the lift.The re-searchers found that the ratio changed from 1.1:1.0at 50%of 1RM to 1.5:1.0at 90%of 1RM.The proportional contri-bution of hip extension moments at 90%of 1RM was 33.3%greater than at 50%of 1RM.This shows us that as the weights get heavier in squats,the hips display a proportionally greater increase in exten-sor moment than the knees (Figure 1).

HOW DOES HIP EXTENSION IMPULSE AND WORK CHANGE WITH INCREASING LUNGE LOAD?

Recent research indicates that hip extension impulse increases with increasing load to a greater extent than knee extension impulse during the lunge.Riemann et al.(10)inves-tigated the differences in the work done and the net joint moment im-pulses during the concentric phase at the hip,knee,and ankle joints during lunges with loads equal to 12.5%,25%,and 50%of bodyweight (Table 2).The researchers found that as the external load increased,the greatest increase in net joint impulse and work done occurred at the hip,followed by the ankle and then the knee.This suggests that as weight is added to the lunge exercise,it becomes increasingly reliant on the hips for progression.Again,the ratio of hip-to-knee extension impulses increases with increasing load.The researchers

found that the ratio changed from 3.4:1.0at 12.5%of additional body-weight loading to 4.2:1.0at 50%of additional bodyweight loading.The proportional contribution of hip exten-sion impulse at 50%of additional body-weight loading is 22.8%greater than at 12.5%of additional bodyweight loading.This shows us that as the weights get heavier in lunges,the hips display a pro-portionally greater increase in impulse than the knees (Figure 2).

HOW DO HIP EXTENSION MOMENTS CHANGE WITH

INCREASING DEADLIFT LOAD?

Recent research indicates that the hip extension moment increases with increasing load by proportion-ally more than the knee extension moment during the conventional deadlift.Swinton et al.(14)investi-gated the peak net hip,knee,and ankle moments during straight bar conventional deadlifts and hex-bar deadlifts (Table 3).The researchers found that as the load lifted increased,there was a proportionally greater increase in hip extension mo-ments compared with the knee or ankle moments.Hence,the hip-to-knee extension moment ratio increased with increased loading.The researchers found that the hip-to-knee extension moment ratio for the straight bar conventional deadlift increased from 2.8:1.0at 10%of 1RM to 3.7:1.0at 80%of 1RM.This represented an increase in hip-dominance of 33.3%.Similarly,they found that the hip-to-knee extension moment ratio for the hex-bar deadlift increased from 1.70:1.0at 10%of 1RM to 1.78:1.0at 80%of 1RM.This represents an increase of 5.1%in hip involvement.The increase in the hip-to-knee extension moment ratio is greater in the conventional dead-lift compared with the hex-bar deadlift for the same relative increase in the load lifted.Both deadlift variations display an increase in hip involvement as the load is increased,just as is seen in the squat and in the lunge exercises,but the increase in hip involvement in the hex-bar deadlift was much smaller

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in the conventional deadlift.This shows us that as the weights get heavier in conventional deadlifts,the hips display a proportionally greater increase in moments compared with the knees (Figure 3).

HOW DO HIP EXTENSION MOMENTS CHANGE WITH

INCREASING RUNNING SPEED?

Recent research indicates that hip extension moments increase with increasing speed to a greater extent than knee extension moments during running at different speeds.Schache

et al.(11)investigated the joint mo-ments during running at various speeds (Table 4).They recorded moments at different points in the gait cycle,and the greatest hip extension moments were recorded during terminal swing.It was found that the ratio of hip-to-knee extensor moments increased with increasing running speed,suggesting that the hips become progressively more involved at greater velocities.At 3.5m/s,it was found that the ratio of peak hip-to-knee extensor moments was 0.29:1.0,whereas at 8.95m/s (considered “sprint running”),the

ratio of peak hip-to-knee extensor moments was 1.18:1.0.This shows that the hips became 304%more involved as running speeds progress from 3.5m/s to 8.95m/s and that the activity of running shifts from knee-dominance to hip-dominance (i.e.,greater hip than knee extensor mo-ments)as a result.This shows that as running speed increases,the hips dis-play a proportionally greater increase in moments compared with the knees (Figure 4).

HOW DO HIP EXTENSION MOMENTS CHANGE WITH

INCREASING JUMPING HEIGHT?

Recent research indicates that hip extension moments increase with increasing jump height to a greater extent than knee extension moments.Lees et al.(8)studied jumps of 3differ-ent intensities,which they labeled “low,”“high,”and “maximum”(T able 5).The low jump averaged 35cm,the medium jump 44cm,and the maximum jump height 53cm.Lees et al.(8)re-corded the joint moments and the work done at each joint during the various jumps and found that the work done at the hip increased markedly with increasing jump height but the work done at the ankle and knee did not increase relatively to the same extent.Joint moments followed a similar trend.Consequently,it was found that the ratio of hip-to-knee work done in the concentric phase increased from 0.64:1.0in the low jump (i.e.,the jump was actually knee-dominant)to 1.67:1.0in the maximal jump.This represented an increase in hip involvement of 163%and a shift from knee-dominance to hip-dominance as a result.This shows us that as jumping height increases,the hips display a proportionally greater increase in work done (and

extension

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moments)compared with the knees (Figure 5).

WHAT IS THE ROLE OF THE HIP EXTENSORS IN LATERAL MOVEMENTS?

Although all the above movements occur primarily in the sagittal plane,2recent studies have investigated the role of the hip extensors in side-stepping.Inaba et al.(6)found that hip extension moments increased signi?cantly with increasing side step distances but hip abduction moments did not.Similarly,Shimokochi et al.(12)reported that hip abductor function did not seem to be the crit-ical factor for lateral movements but rather that faster hip extension motions were the key to more explo-sive movements in the frontal plane.

WHY DOES THE ROLE OF THE HIP INCREASE WITH INCREASING INTENSITY?

The ?ndings of these studies indicate that the ratio of hip-to-knee extensor moments or related variables increases with heavier loads during squats,lunges,deadlifts,and hex-bar dead-lifts (Table 6).Additionally,the stud-ies indicate that the ratio of hip-to-knee extensor moments or related variables increases with greater speeds in running and with greater heights in jumping.This may happen as a result of different movement strategies being used with different loads and speeds,as indeed Frost et al.(4)recently observed.Frost et al.(4)found that when performing lifting or squatting tasks with a faster movement speed,subjects used a less upright posture and shifted to a more hip-dominant pattern involving an increase in trunk inclination toward the horizontal.Such alterations in kinematics would be expected to lead to corresponding changes in kinetics.Indeed,Hay et al.(5)observed a simultaneous change in trunk incli-nation along with a proportionally greater increase in hip extension moment during squat exercises with increasing load.However,exactly what drives this change in

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kinematics and kinetics of the move-ment patterns as intensity increases is unclear.It is possible that as the demand of the movement increases,individuals ?nd they are able to move faster or lift heavier by leaning for-ward more,which may then lead to a shift in the proportion of hip and knee extension moments in favor of the hip.Because athletes typically display signi?cantly greater hip extension moments than knee extension moments during maximal isometric testing (e.g.,Bu s ko and Gajewski (3)),it may be the case that this shift occurs because the hip muscles are stronger than the knee muscles and therefore pro-vide greater scope for increased moments.However,because maxi-mal isokinetic moments do not dem-onstrate such clear differences between the magnitude of hip and knee extension moments at all angu-lar velocities (e.g.,Smith et al.(13)and Blazevich and Jenkins (1)),the exact reasons for the changes remain unknown.

PRACTICAL IMPLICATIONS

The 5examples shown in this article demonstrate that as loads get heavier (squat,lunge,conventional deadlift,and hex-bar deadlift),running gets faster,and jumps get higher,hip extension moments or related varia-bles contribute proportionally more to the movement and knee extension moments or related variables contrib-ute proportionally less (Figure 6).Similarly,faster lateral movements require greater increases in hip exten-sion moments than hip abduction moments.This means that for ath-letes training to produce maximal power and speed,whether in the sag-ittal or frontal plane,developing the muscular strength of the primary hip extensors (i.e.,the gluteus maximus and hamstrings)must be a primary concern.

For athletes training with exercises that closely resemble their competi-tive activities (e.g.,sprinters sprinting or powerlifters squatting),it is

likely

and Lees et al.(8).

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that submaximal performances will involve signi?cantly lower hip-to-knee extension moments.Therefore, strength coaches will want to address this de?cit.The de?cit could be ad-dressed in several ways.First,addi-tional work could be performed for the hip extensors.This could take the form of assistance work in the gym,comprising hip-dominant com-pound movements such as Romanian deadlifts,good mornings,back exten-sions,reverse hypers,barbell hip thrusts and/or kettlebell swings,and waist-attached sled dragging,which has been shown to be superior to shoulder-attached sled dragging in terms of hip extensor moments(7). Second,maximal work could be emphasized and submaximal work de-emphasized,to the degree that this is possible within the periodized program that the coach considers necessary for the long-term develop-ment of the athlete.Finally,although most researchers have emphasized the optimal load for power training as being the load that leads to the greatest overall power output,it may be more fruitful to train with the load that maximizes power out-put at the hips.Moir et al.(9) recently reported that power output was maximized at the hip during jump squats at42%of1RM,whereas system power output was maximized with no load(i.e.,0%of1RM). Future research should be conducted to determine the optimal loads for hip extension power with other

explosive lifts,and to determine

whether training at these loads is

more bene?cial for performance

than training at optimal loads for

system power.

CONCLUSIONS

As we have seen in the previous

examples,the ratio of hip-to-knee

extensor moments or related varia-

bles increases with heavier loads

during squats,lunges,deadlifts,and

hex-bar deadlifts.Additionally,the

ratio of hip-to-knee extensor mo-

ments or related variables increases

with greater speeds in running and

with greater heights in jumping.In

these movements,this represents

a shift from knee-dominance at

lower intensities to hip-dominance

at higher intensities.It is not surpris-

ing that the hips produce greater

moments as intensities increase dur-

ing these movements.However,the

fact that the hip moments rise to

a greater extent than knee moments

shows that the mechanics(i.e.,form

or technique)are altered during

these movements in a manner that

relies more on the hips and less on

the knees for propulsion.As force

increases,therefore,the role of the

hip extensors becomes much more

important and their contribution to

the movement increases.This has

important rami?cations for training

and performance.

Con?icts of Interest and Source of Funding:

The authors report no con?icts of interest

and no source of

funding.

Chris

Beardsley is the

Director of

Strength and

Conditioning

Research

Limited.

Bret Contreras

is currently pur-

suing his PhD at

AUT University.

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