Eva A. Andersson

The role of the psoas and iliacus muscles for stability and movement of the lumbar spine, pelvis and hip

The activation patterns of the psoas and iliacus muscles were investigated in 7 healthy adult subjects (4 men and 3 women) during a variety of motor tasks in standing, sitting and lying. Myoelectric activity was recorded simultaneously from the 2 muscles using thin wire electrodes inserted under guidance of high‐resolution ultrasound. In general, both muscles were coactivated, albeit to different relative levels, particularly when hip flexor torque was required. Selective activation of the iliacus could, however, be seen to stabilize the pelvis in contralateral hip extension during standing. Psoas was found to be selectively involved in sitting with a straight back and in contralateral loading situations requiring stabilization of the spine in the frontal plane. During training exercises from a supine position, such as sit‐ups, the contribution of the psoas and iliacus muscles could be varied by changing the range of motion as well as the position and support for the legs. Thus, the 2 anatomically different muscles of the iliopsoas complex were shown to have individual and taskspecific activation patterns depending on the particular demands for stability and movement at the lumbar spine, pelvis and hip.

Abdominal and hip flexor muscle activation during various training exercises

Abstractu2002The purpose of this study was to provide objective information on the involvement of different abdominal and hip flexor muscles during various types of common training exercises used in rehabilitation and sport. Six healthy male subjects performed altogether 38 different static and dynamic training exercises – trunk and hip flexion sit-ups, with various combinations of leg position and support, and bi- and unilateral leg lifts. Myoelectric activity was recorded with surface electrodes from the rectus abdominis, obliquus externus, obliquus internus, rectus femoris, and sartorius muscles and with indwelling fine-wire electrodes from the iliacus muscle. The mean electromyogram amplitude, normalised to the highest observed value, was compared between static and dynamic exercises separately. The hip flexors were highly activated only in exercises involving hip flexion, either lifting the whole upper body or the legs. In contrast, the abdominal muscles showed marked activation both during trunk and hip flexion sit-ups. In hip flexion sit-ups, flexed and supported legs increased hip flexor activation, whereas such modifications did not generally alter the activation level of the abdominals. Bilateral, but not unilateral, leg lifts required activation of abdominal muscles. In trunk flexion sit-ups an increased activation of the abdominal muscles was observed with increased flexion angle, whereas the opposite was true for hip flexion sit-ups. Bilateral leg lifts resulted in higher activity levels than hip flexion sit-ups for the iliacus and sartorius muscles, while the opposite was true for rectus femoris muscles. These data could serve as a basis for improving the design and specificity of test and training exercises.

Diverging intramuscular activity patterns in back and abdominal muscles during trunk rotation.

Study Design. An intramuscular electromyographic study was performed on trunk rotations during sitting and standing. Objective. The aim was to provide new information on activation levels for deep trunk muscles in various unresisted and resisted trunk rotations. Summary and Background Data. Frequent daily trunk twisting and decreased maximal strength during trunk rotation have been associated with low back pain or sciatic pain. However, the involvement of deep trunk muscles during different trunk rotations is relatively unknown. Methods. Ten healthy subjects participated. Fine-wire electrodes were inserted, under ultrasound guidance, into psoas, quadratus lumborum, the superficial medial lumbar erector spinae (ES-s, multifidus) and its deep lateral portion (ES-d, iliocostalis), iliacus, rectus abdominis, obliquus externus, and obliquus internus. Results. The highest involvement for all muscles was observed on the ipsilateral side, in maximal trunk twists with shoulder resistance, except obliquus externus, which showed a dominant contralateral side, and rectus abdominis, which was little activated in all rotations. In contrast, maximal trunk twist without shoulder resistance, i.e., freely performed, resulted generally in lower levels for all muscles involved and in a shift of side dominance for the lumbar muscles quadratus lumborum, psoas, and ES-s. Conclusions. During trunk rotations the activity patterns for various trunk muscles could drastically change, and even be the opposite, between the two body sides, within the same type of task, depending on several factors such as initial position, effort level, sitting or standing, and external shoulder resistance.

Movement and muscle activity pattern in wheelchair ambulation by persons with para- and tetraplegia

The patterns of movement and muscle activation in wheelchair ambulation have been studied in two groups: subjects with paraplegia (n = 4) and tetraplegia (n = 3). All subjects were physically active and experienced wheelchair users. The tests were done in the subjects own wheelchairs and under free-wheeling conditions. The tasks studied were: self-chosen normal velocity, maximal velocity and maximally accelerated start. Muscle activation was registered by surface electromyography performed on several arm and shoulder muscles. The movement pattern was studied by goniometry of the shoulder and elbow joints, as well as by observing video recordings. Speed and arm cycle frequency were also recorded. The movement pattern was divided into three phases: pull, push and recovery. Relatively concordant muscle activation patterns were noted within the groups, whereas differences were noted between the groups with regard to muscle activation, length of the pull and push phases and the velocity-dependent adaptation. The subjects with tetraplegia were more dependent on the pull phase. The self-chosen normal and maximal speeds of the subjects with tetraplegia were approximately half those of the subjects with paraplegia. Three different types of recovery movements were noted as well as a velocity-dependent adaptation. Major trunk movements during the rim phase were only noted at the maximally accelerated start. In conclusion, the results point to both similarities and differences in the movement pattern and muscle activation in individuals with para- and tetraplegia under different ambulation conditions. The differences are of such a magnitude that they are important enough to consider when teaching wheelchair techniques and developing rehabilitation programmes for different groups of patients with spinal cord injuries.

Relative EMG levels in training exercises for abdominal and hip flexor muscles.

The main purpose of our study was to compare systematically EMG levels in sub-maximal training exercises for the trunk and hip flexor muscles with those voluntarily attainable in corresponding situations. Six healthy subjects performed three types of standardized training exercises, whose static positions, movement velocity and range of motion were reproduced during maximal voluntary isokinetic strength tests. EMG was recorded with wire electrodes from the iliacus muscle and with surface electrodes from the rectus femoris, sartorius, rectus abdominis, obliquus externus and internus muscles. The relative EMG values demonstrated a task dependency which could differ between individual muscles. The maximal voluntary activation levels were relatively constant across conditions. Exceptions were present, particularly for the rectus femoris and iliacus muscles. These findings highlight the consequences of using different methods of normalizing EMG. The relative EMG values presented may serve as guidelines when selecting training exercises for specific trunk and hip flexor muscles in sports and rehabilitation.

Maximal Aerobic Power versus Performance in Two Aerobic Endurance Tests among Young and Old Adults

Background: Aerobic fitness is of great value for reducing risk of mortality and cardiovascular diseases. Objective: This study evaluated the performance in and correlations between a new test (five-minute pyramid test, 5MPT), the six-minute walk-test (6MWT) and maximal oxygen uptake (VO2max) among old and young adults. Methods: Forty-four habitually active adults (females and males), 23 old (64–79 years) and 21 young (20–32 years) participated. In the 5MPT, the participants moved back and forth along a short walkway (5.5 m) over boxes (height: ‘old people’ 0.42 m, ‘young people’ 0.62 m) arranged like an elongated step pyramid for 5 min. Power in the pyramid test (5MPTpower) was calculated as the product of numbers of laps, body weight, gravity and highest box level divided by time. A 6MWT and a maximal cycle ergometer test for direct measurements of VO2max were also performed. In all tests heart rate, with on-line electrocardiography, and perceived exertion were recorded. Results: There was a strong correlation between the 5MPTpower and VO2max for the entire group studied (r = 0.98), and each of the four subgroups old and young females and males separately (r = 0.78–0.98). Contrary to several earlier studies, especially involving people with various diseases, the present data showed that 6MWT cannot be used to predict VO2max among old females and young adults. The correlation with VO2max was weaker for the 6MWT than for the 5MPTpower. The relative performance values for the old compared to the young (ratio old/young × 100) were considerably lower in 5MPTpower and VO2max (47–55%) than in distance and ‘work’ in the 6MWT (82–86%). Conclusions: The results, with age and gender variations, can be valuable information in health-fitness contexts, since measuring physical aerobic capacity is very significant in connection with risk evaluations of mortality and various diseases. The 5MPT is a rapid, functional, easy and inexpensive tool for predicting assessed maximal aerobic power.

Contents Vol. 57, 2011

Behavioural Science Section K.J. Anstey, Canberra L. Clare, Bangor D. Gerstorf, Berlin J.D. Henry, Sydney T. Hess, Raleigh, N.C. S.M. Hofer, Victoria I. Kryspin Exner, Wien D.C. Park, Dallas, Tex. K. Ritchie, Montpellier J. Smith, Ann Arbor, Mich. Experimental Section C. Bertoni-Freddari, Ancona R. Faragher, Brighton C. Franceschi, Bologna T. Fülöp, Sherbrooke L. Gavrilov, Chicago, Ill. L. Haynes, Saranac Lake, N.Y. K. Hirokawa, Tokyo G.J. Lithgow, Novato, Calif. M. Rose, Irvine, Calif. A. Viidik, Wien J. Vijg, Bronx, N.Y.