Recruitment of Internal Oblique and Transversus Abdominis ... | Summaries Biomechanics

Recruitment of Internal Oblique and Transversus

Abdominis Muscles During the Eccentric Phase of the

Curl-up Exercise

MARILYN I. MILLER

and JOHN M. MEDEIROS

The purpose of this study was to analyze the results of a training method to

increase voluntary recruitment of internal oblique and transversus abdominis

muscles. Forty volunteers were assigned to either a Control or an Experimental

Group. Training consisted of multisensory (auditory, tactile, visual, and kines-

thetic) cuing focused on the lower abdominal muscles during the slow curl-back

(eccentric) phase of curl-up exercises with the subjects' feet unsupported. We

recorded integrated electromyographic (IEMG) values using surface electrodes

from internal oblique and transversus abdominis muscles during pretest and

posttest exercises. Using an analysis of covariance, posttest

IEMG

values of the

Experimental Group were significantly higher (p < .001) than the Control Group.

Our results reveal that multisensory cuing with the feet unsupported during the

curl-back is an effective method of increasing combined recruitment of internal

oblique and transversus abdominis muscles. Motor skills developed by this

technique are discussed in relation to optimal trunk function and rehabilitation.

Key

Words:

Abdominal

wall,

Exercise

therapy,

Physical

therapy.

Common adult disorders

of the

trunk, such

as low

back

pain and inguinal hernias, are associated with weakened lower

abdominal muscles

and

their improper

inadequate

use in

daily activities.1-7

sedentary individuals, trunk muscle

im-

balance develops that favors strength

postural muscles,

such

as the

iliopsoas, compared with weakness

the more

phasically acting abdominal muscles.7

addition,

the

ilio-

psoas muscle, with

its

extensive lumbar attachment, contrib-

utes potentially hazardous compressive and lordotic forces on

the lumbar spine8

and

intervertebral disks,9

if not

balanced

by the stabilization forces

the

abdominal muscles.3,7,8

Awareness and recruitment

abdominal muscles

exer-

cise

and

daily activity appear

to be

required

maintain

balance

the trunk musculature. Thus, training should

directed toward voluntary recruitment

abdominal muscles

during common trunk training exercises such as the curl-up.

Using electromyography, Janda

and

Schmid showed that

stabilizing the feet dorsally during curl-ups facilitates iliopsoas

muscle predominance.7 Controlling

the

curl-up without

the

feet anchored requires pelvic stabilization

and

trunk coordi-

nation skills, which

are

essential

for

functional trunk train-

ing.3,10

pilot study,

used intramuscular EMGs recorded

from fine-wire electrodes

examine

the

relationship

the

iliopsoas, abdominal,

and

gluteus maximus muscles during

curl-ups, with

and

without dorsal foot stabilization.

Our

raw

EMG data recorded from three subjects support the results of

Janda

and

Schmid7

and

suggest that

inverse relationship

exists between internal oblique

and

iliopsoas muscle activity

during

the

curl-back (eccentric) phase

curl-ups.

other

abdominal muscles appeared

to be so

closely related

ilio-

psoas muscle activity during curl-ups. After training,

the

individuals' iliopsoas muscle activity decreased, whereas

the

activity

the abdominal muscles, particularly

the

internal

oblique muscle, increased markedly.

This apparent substitution would

anticipated from

the

anatomical

and

kinesiological similarities

the two muscles

(Fig. 1). Both

the

internal oblique

and the

iliopsoas muscles

are attached dorsally

and

ventrally and apply forces onto

the

pelvis

and the

spine

(the

iliopsoas muscle directly

and the

internal oblique muscle through

its

attachment

to the lum-

bodorsal fascia). The internal oblique and transversus abdom-

inis muscles

are the

only

two

abdominal muscles that

are

attached from

the

anterior trunk

to the

lumbar spine

by the

lumbodorsal fascia,

the

strongest

low

back supportive struc-

ture.3,11

They also

are the

only abdominal muscles passing

superior

to the

inguinal canal that supply active support

response

intra-abdominal pressure.6

Authors

previous studies

abdominal muscle exercise

have examined different muscle groups with different meth-

ods.

They have focused

on the

activity

the prime movers,

specifically

the

rectus abdominis

and

external oblique mus-

cles,

rather than

the

stabilizing muscles that encircle

the

trunk—the internal oblique

and the

transversus abdominis

muscles.12-18 Previous studies have

not

incorporated motor

learning techniques

for

facilitating trunk

and

hip flexor mus-

cle coordination.12-19

The objective

this study was

examine

method that

has been used clinically

teach individuals

to end

their

Ms.

Miller

is in

private practice

in low

back education

and

rehabilitation

Neskowin,

OR, and San

Francisco,

CA. She was a

graduate student, Physical

Education Department,

San

Francisco State University, when this study

was

completed

partial fulfillment

of her

Master

Arts degree. Address corre-

spondence

to 112

Montcalm

St, San

Francisco,

94110 (USA).

Dr. Medeiros

Director, Motion Analysis Laboratory, Children's Hospital

at Stanford,

520

Willow

Rd,

Palo Alto,

94304.

This article

was

submitted November

12, 1985; was

with

the

authors

for

revision

weeks;

and was

accepted September 25,

1986.

Potential Conflict

Interest:

Volume 67 / Number 8, August 1987

1213

Recruitment of Internal Oblique and Transversus Abdominis ..., Summaries of Biomechanics

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