Comparison of muscular activities in the abdomen and lower limbs while performing sit-up and leg-raise (2024)

Abstract

[Purpose] This study compared the muscle activities of sit-up and leg-raise. [Subjectsand Methods] The subjects of this study were healthy students in their 20s. Forelectromyography of sit-ups and leg-raises in the supine position, 5 muscle groups of theabdomen were selected for the attachment of sensors: the upper and lower rectus abdominis,external oblique, rectus femoris, and the iliopsoas. SPSS 20.0 was used for thestatistical analysis. One-way ANOVA with repeated measures of all factors was performed toverify the statistical significance of the measurements taken for the muscle activitiesand follow-up verification was made with the Bonferroni post hoc test. [Results] Sit-upand leg raise showed a significant difference. The eccentric sit-up exercise elicited asignificant increase in the activation of the abdominal muscle. The leg raise andeccentric sit-up exercises elicited significant increases in the activation of hip flexormuscle. [Conclusion] The eccentric sit-up had the most outstanding effect on the abdominalmuscles involved in stability of the trunk.

Key words: Low back pain

INTRODUCTION

The majority of people living in the modern era experience lumbar pain, and although thereare numerous ways of reducing the pain, recent focus has been placed on the reinforcement ofabdominal muscle strength through exercise therapy. Kim¹⁾ compared the contraction ability of the abdominal muscle betweenlumbar pain patients and normal people. The results showed that lumbar pain patientsdisplayed a lower level of contraction ability in the abdominal muscles compared to normalpeople. Reinforcement of the abdominal muscles play an important role in the treatment andprevention of lumbar pain²⁾. The abdominalmuscles are very important, since they assist the harmonious movement of the limbs andmaintain the stability of the axis of the human body³⁾.

Exercising the abdominal muscles is aimed not only at improving body control, but also atfortifying muscular endurance⁴⁾. Methods ofreinforcing the abdominal muscles include sit-ups, straight leg-raises, etc. In addition, itis possible to effectively reinforce the abdominal muscles by using a diverse range ofexercise equipment⁵⁾. Gurmaraes⁵⁾ asserted that sit-ups fortify the upperrectus abdominis while straight leg-raises in the supine position target the lower rectusabdominis. In addition, Vera-Garcia et al.⁶⁾ asserted that various abdominal muscles must be activatedsimultaneously, rather than a single abdominal muscle, in order to maintain stability of thebody. However, there is inadequate research regarding the activation of the overallabdominal muscles when performing sit-ups and straight leg-raises in the supine position,and these are the most common exercises performed for strengthening the abdominalmuscles.

This study selected 2 representative methods of reinforcing the abdominal muscles, andmeasured and analyzed the extent to which the abdominal muscles were activated whileperforming these exercises.

SUBJECTS AND METHODS

Twenty healthy adult males and females attending D University were selected as the subjectsof this study. The subjects were informed of the study purpose and methods, and they signedan informed consent form. Subjects recruited for this study had no neurological problems ormusculoskeletal diseases. The subject characteristics were as follows (subject mean age:20.5 yrs; 8 males, mean age: 20.5 yrs, mean height: 173.4 cm, mean weight: 65.3 kg; 12females, mean height: 161.4 cm, mean weight: 53.4 kg).

For the electromyography of sit-ups and leg-raises in the supine position, 5 muscle groupsof the abdomen were selected for the attachment of sensors: the upper and lower rectusabdominis, external oblique, rectus femoris, and iliopsoas⁷⁾. For the upper and lower rectus abdominis, sensors were situated atthe center of the abdomen above and below the navel separated by a gap of 3 cm. For theexternal oblique, sensors were attached in the direction of the grain of the muscular fiberbetween the right ribs and iliac crest, and along the median line of the armpit. For therectus femoris, sensors were attached to the most protruding portion at the mid-point of thestraight line that connects the ASIS and the central portion of the patella. For theiliopsoas, the sensor was attached to the medial aspect of the rectus femoris, inferior tothe inguinal ligament.

After attaching the sensors for the electromyography, maximal voluntary isometriccontraction (MVIC) was executed in the manual muscular strength test posture to obtainnormalization values prior to the commencement of this experiment. Measurements of the MVICvalues were made 3 times in each posture over a period of 5 seconds for each measurement.The 5-second electromyogram data converted to root mean square (RMS) values and the averagestrength of the electromyogram signal during the middle 3 seconds, excluding the first andthe last second, was used as the 100% MVIC value in the analysis. A Telemyo 2400TG2electromyogram (Noraxon USA, Inc. Scottsdale, AZ, USA) was used to record theelectromyograms and the Myoresearch XP Master Edition from Noraxon was used for dataanalysis. A frequency of 1,500 Hz was used for the collection of the data.

The subjects were instructed to perform sit-ups and leg-raises in the supine position. Atotal of five measurements were made, with a period of rest of one minute between eachmeasurement. For sit-ups, the knee joints were bent at an angle of 100°, with both handscrossed and placed on the chest while the ankles were held down. The concentric movement oflifting the trunk was performed for 3 seconds followed by the eccentric movement of loweringthe trunk for 3 seconds. For the straight leg-raise in the supine position, both hands wereplaced next to the trunk and both shoulders were held down to prevent compensating action.The concentric movement of raising the legs was performed for 3 seconds followed by theeccentric movement of lowering the legs to the floor for 3 seconds. All experiments wereapproved by the Ethics Committee of Catholic University (CUPIRB-2015-012) of Pusan.

SPSS 20.0 was used for the statistical analysis. One-way ANOVA with repeated measures forall factors was performed to verify the statistical significance of differences in the upperand lower rectus abdominis, external oblique, rectus femoris and iliopsoas, and follow-upverification was made with the Bonferroni post hoc test.

RESULTS

The results of abdominal exercises were analyzed by repeated measure ANOVA and asignificant difference in the interaction between abdominal exercise type and muscleactivation (p<0.05) was found. The abdominal muscles displayed significant differences(p<0.05) between the exercises as illustrated in Table 1. The results of the follow-up verification are as follows.

DISCUSSION

This study compared the muscular activities of the upper and lower rectus abdominis, theexternal oblique, iliopsoas, rectus femoris between sit-ups and leg-raises usingelectromyography, and also examine the differences in concentric and eccentriccontractions.

Reinforcement of the abdominal muscles is a widely-used method for prevention and treatmentof lumbar pain. In addition, actions of the abdominal muscle perform the role of stabilizingthe lumbar region by increasing the intra-abdominal pressure and extending the thoracolumbarfascia. Therefore, reinforcement of the abdominal muscles is extremely important forreduction of lumbar pain⁸⁾.

Many lumbar pain patients display weakened abdominal muscle strength⁹⁾. This study used electromyography in order to find the mosteffective exercise for reinforcement of the abdominal muscles. For the activation of theupper and lower rectus abdominis and the external oblique, the sit-up was found to be moreeffective than the straight leg-raise. However, for the activation of the iliopsoas andrectus femoris, the straight leg-raise was found to be more effective than the sit-up. Onthe basis of the present results of this study, it can be concluded that the sit-up is anexercise that facilitates activation of the abdominal muscles with low activation of thelower limb muscles.

In order to appropriately stabilize the trunk, it is necessary to optimally align the bodybetween the pelvis and spine, and prevent excess movement of the pelvis as well as stresswhile the limbs are moving¹⁰⁾. Whenengaging in the exercise of the abdominal muscles, it is not only the abdominal muscles thatcontract, but also the iliopsoas and rectus femoris, as they are attached to the trunk(spine and pelvic girdle). At the time of performing sit-ups, excessive contraction of theiliopsoas muscle or rectus femoris can damage the lumbar vertebrae¹¹⁾. In order to avoid this possibility, sit-ups must beperformed using a trunk curl movement while reducing active hip flexion¹¹⁾. On the other hand, the straight leg-raise is deemed to bemore appropriate for the reinforcement of the flexors since the activation of the flexors ofthe lower limbs is high while the activation of the abdominal muscles is low. Use of theflexors of the lower limbs should be avoided while exercising the abdominal muscles since itwould aggravate the condition of patients with lumbar pain. According to the results of thisstudy, the sit-up effectively reinforces the movement of the lower limbs on the stability ofthe trunk.

This study investigated the most effective abdominal exercise by measuring the muscularactivities of the upper and lower rectus abdominis, external oblique, iliopsoas and rectusfemoris. The eccentric sit-up had the most outstanding effect on abdominal muscles involvedin the stability of the trunk.

Acknowledgments

This study was supported by a Dong-Eui Institute of Technology Research Grant in 2015.

REFERENCES