Evidence of increased axillary blood flow velocity without increased handgrip strength and endurance in persons with a fibromuscular axillary arch.

BACKGROUND: The purpose of this in vivo study was to compare axillary artery blood flow velocity, and maximal handgrip strength and endurance performance in young subjects with and without an axillary arch (AA). MATERIALS AND METHODS: One hundred and fifty-six young adults were screened for the presence of an AA on their dominant arm side. After physical examination subjects were checked using diagnostic echography for the presence of an AA. Sixteen subjects with an AA and 15 without an AA had their axillary artery peak systolic velocity quantified in 3 different arm positions using Doppler ultrasound. Maximal handgrip strength and endurance performance was quantified in the same positions using a functional rehabilitation system. RESULTS: Mean peak systolic velocity was significantly higher in the AA group compared to controls in abduction/external rotation of the arm during muscle relaxation (p = 0.003) and contraction (p = 0.01). No significant differences between groups were found for maximal handgrip strength and endurance performance. CONCLUSIONS: This study provides evidence for a transient axillary artery compression by the AA in a throwing position. This is not reinforced by additional contraction of the shoulder muscles along with the AA. Axillary artery compression does not influence maximal handgrip strength and endurance performance in symptom-free young adults.

Direct relationship of body mass index and waist circumference with body tissue distribution in elderly persons.

OBJECTIVES: To explore the relationship of BMI and WC with muscle/adipose tissue mass ratios and with trunk adipose tissue distribution, based on an anatomical 5-compartment model, by dissection of cadavers of elderly persons. DESIGN: Cross-sectional explorative study. SETTING: Brussels Cadaver Analysis Study. PARTICIPANTS: Cadavers of twenty-nine white Caucasian elderly persons (17 females and 12 males, aged 78.1±6.9 years). MEASUREMENTS: Whole body and trunk composition were determined at the anatomical tissue-system level by direct dissection. RESULTS: BMI and WC were significantly and positively related to absolute tissue masses in both sexes. Muscle tissue mass, adipose tissue mass and trunk internal adipose tissue mass correlated better with BMI (r-values between 0.68 and 0.89) than with WC (r-values between 0.49 and 0.71). BMI was significantly and inversely related with various muscle/adipose tissue ratios in both sexes (r-values between -0.54 and -0.68). WC correlated with muscle/adipose tissue ratios in females only (r-values between -0.55 and -0.64). BMI was also significantly related to trunk adipose tissue distribution in elderly females, but not in males. When comparing individual tissue proportions within and between adjacent BMI-classifications or WC categories, body composition varied considerably. CONCLUSION: Our results show that BMI and WC are significantly related with adipose tissue mass and with several ratios of muscle to adipose tissue in elderly subjects. However, cautious clinical interpretation is warranted since important differences in tissue mass proportions were found in subjects with similar BMI and/or WC values.

Quality control of 157 whole body adiposity prediction formulae in age and activity matched men.

AIM AND METHODS: The physiological and clinical importance of body composition is part of public health, nutrition and Sports medicine. The most popular field method for estimating total body adiposity remains anthropometry separately or in formulae. The aim of this study was to verify the suitability of an absolute maximum out of more than 600 existing anthropometry equations estimating % adipose tissue (AT) in a cross validation with dual energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA) and hydrodensitometry (HD) on 74 British male subjects (mean age 34.4±14.1) with different lifestyles corresponding to a maximum of populations the original formula was developed for. RESULTS: Pearson correlation coefficients, paired sample t-test and Bland and Altman plots where used for analyses. From the tested formulae, 19 correlated well (r≥0.70) and showed no significant difference (p>0.05) with BIA, 15 with DXA and only 12 with HD. The results show a better match of the predicted % AT by anthropometric equations with BIA then with DXA or HD. CONCLUSION: All results and conditions considered, this study suggest not to use HD nor anthropometric formulae to assess % AT in men for an individual estimation.

Morphology and kinematics of the atlanto-axial joints and their interaction during manual cervical rotation mobilization.

BACKGROUND DATA: At present little data are available on the relationship between spinal anatomy and kinematics. No studies have verified the relationship between atlanto-axial kinematics during manual mobilization and the spatial features of the atlanto-axial ligaments and the lateral joints. MATERIALS AND METHODS: Twenty un-embalmed cervical spine specimens (9 male and 11 female; 80 ± 11 years) were studied. Atlanto-axial kinematics were registered during manual axial rotation mobilization using an ultrasound-based motion tracking system. Anatomical landmarks were digitized and spatial features of the lateral atlanto-axial joint surfaces and alar ligaments were extracted. The relationship between the anatomical features and the spinal kinematics was analyzed using statistical regression analysis. RESULTS: Only the range of motion of the coupled flexion-extension motion component, the ratio and the time shift between main axial rotation and coupled lateral bending motion components could be predicted for about 52%, 49% and 73%, respectively, by a selected set of anatomical features. CONCLUSION: Supposed relationships between anatomical features and joint kinematics are only partially confirmed. The results indicate that the kinematics of the atlanto-axial joint during manual regional axial mobilization are not completely predetermined by the specimens' specific anatomy.

Hazards of hydrodensitometry.

The limitations of the two-component model of body composition have been investigated extensively in the past resulting in a clear message of violation of basic assumptions underlying its use. This strong message may or may not be appropriate, since hydrodensitometry is still used, in particular in sports sciences. The combination of novel information with previously described indicators should allow to confirm or reject the pretended violation of basic assumptions underlying the use of hydrodensitometry. Water content of adipose tissue (AT) and of AT free mass as opposed to fat and fat free mass, and bone density of separate bones was obtained from the Brussels Cadaver Analysis Study collection. Analysis of different studies indicated anomalies up to -12% fat but also suggests that the borderline between chemical and morphological interpretations becomes vague and the ad hoc terminology does not reflect reality. Predicted % body fat using different methods on the same individual ranges between 9.6% up to 21% of AT. Total body water of separate tissues suggests intra-and intervariability within tissues. Whole skeleton density and the separate bone density cannot support the two-component constancy (1.164 g/mL to 1.570 g/mL).

Direct measurement of tibial cortical bone surface area.

Cortical bone surface area estimation is generally performed by analysis of medical images but its accuracy has not yet been verified by direct bone measurements. This study was performed to evaluate the reproducibility of direct ex vivo estimations of cross sectional tibial cortical bone surface area. Ten tibiae were evaluated by two observers using direct 3D-digitization at 38 and 66% of total tibial length using a 'critical' and a 'general' criterion for differentiation between cortical and cancellous bone. The results of the analysis using the more severe 'critical' differentiation criterion yielded high intra and interobserver agreement. Mean intraobserver reliability was demonstrated by R = 0.98 (Spearman rank correlation between 0.98 and 0.97; P < 0.01) and inter observer reliability by R = 0.91 (Spearman rank correlation between 0.95 and 0.88; P < 0.01). When using strict criteria to differentiate between cortical and cancellous bone, intra and interobserver reliability of the presented method of direct cortical bone surface area estimation is very high. The results indicate that cross-sectional cortical bone surface estimation by direct 3D-digitization can serve as a gold standard for validation of other estimations methods.

Body mass index as a measure of bone mass.

AIM: BMI is an indicator of body composition (BC) and adiposity in particular. This status is the result of good correlations with indirect (e.g. predictive) two- and three-component models predicting body fat. Aim of the study is to measure the direct relation of BMI with total and segmental BC, e.g. of skin, muscle, bone, viscera and adipose tissue. METHODS: BC constituents of 29 white elderly persons (17 females and 12 males, aged 78.1+/-6.9 years) were determined by direct dissection. Correlations and stepwise linear regression analysis with BMI (dependent variable) and all BC constituents (independent variables) were calculated. RESULTS: All tissues dissected indicated a too high unexplained variance except for bone that accounted for 84% of BMI variance in females and 61% in males (P<0.001). No other constituents improved the prediction. CONCLUSION: The BMI cannot be an appropriate adiposity index. The high proportion of unexplained variance between BMI and direct BC constituents limit its use as a whole body and as a segmental BC index. The BMI could be an index for Bone Mass instead.

Reproducibility of kinematic motion coupling parameters during manual upper cervical axial rotation mobilization: a 3-dimensional in vitro study of the atlanto-axial joint.

INTRODUCTION: The reproducibility of the 3-dimensional (3D) kinematic aspects of motion coupling patterns of segmental manual mobilizing techniques is not yet known. This study analyzes the segmental 3D aspects of manual mobilization of the atlanto-axial joint in vitro. METHODS AND MATERIALS: Twenty fresh human cervical specimens were studied in a test-retest situation with two examiners. The specimens were manually mobilized using three different techniques: a regional mobilization technique, a segmental mobilization technique on the atlas with manual fixation of the axis and a segmental mobilization applying a locking technique. Segmental kinematics were registered with a Zebris CMS20 ultrasound-based tracking system. The 3D aspects of motion coupling between main axial rotation and coupled lateral bending were analyzed by six parameters: the range of motion the three motion components, the cross-correlation, the ratio and the shift. RESULTS: The results indicate stronger intra- than inter-examiner reproducibility. The range of motion of the axial rotation component shows a substantial level of intra- and inter-examiner reproducibility (ICC's 0.67-0.76). The parameters describing the coupling patterns show only moderate to substantial intra-examiner reproducibility for the more experienced of the two examiners (ICC's 0.55-0.68). All other correlations were not significant and no differences could be observed between regional versus segmental techniques. CONCLUSION: Reproducibility of segmental 3D-aspects of manual mobilization of the atlanto-axial joint in an in vitro situation can differ between examiners. The results of the present study may indicate a possible tendency to higher reproducibility if mobilizations are performed by an examiner with high expertise and experience in applying the specific techniques. Continued investigation including more examiners with different levels of experience and different techniques is necessary to confirm these observations.

The role of the axillary arch (of Langer) in the management and the kinesiology of the overhead shoulder mobility.

AIM: Based on cadaveric, neurosurgical and medico-diagnostic evidence the axillary arch of Langer (AA) is assumed to create symptoms similar to those of entrapment or obstruction type syndromes, e.g. Thoracic Outlet Syndrome. Although the incidence of a AA varies between studies and races, there are many assumptions that its frequency and its axillary location influences the motor control of the shoulder girdle. In addition to the existing anatomical evidence and based on functional reasoning it can be predicted that the AA influences the shoulder girdle kinesiology in vivo also. However no study is known that verifies these functional assumptions in vivo. METHODS: In order to complete our knowledge of the AA we evaluated strength, endurance, motor control, precision and proprioception in vivo, e.g. hand held dynamometry, abduction and adduction shoulder strength and endurance, functional exercise assessment, throwing impact force on a (precision) target and shoulder joint position sense were measured in two groups of athletes and physical education students, one with an AA (N.=22) and a control group without AA (N.=22). RESULTS: The results indicate a significant (p<0.05) influence of the presence of an AA on strength, endurance and motor control increase in women associated with an increase of paraesthetics. For all these parameters no significant difference occurred in men. The throwing and proprioceptive joint position sense data however indicate a clear (P<0.05) increase of impact forces suggesting a possible shoulder stabilisation and an improvement of proprioception both in men and most in women. CONCLUSION: These finding have both a functional and clinical relevance and do not fully confirm the anatomical predictions from the cadaveric evidence nor support the (surgical) diagnoses of excision of the AA of Langer in throwing in athletes.

Does manual mobilization influence motion coupling patterns in the atlanto-axial joint?

BACKGROUND: A restricted number of publications have reported on the analysis of coupling patterns in the atlanto-axial joint using an in vitro set-up applying pure moments of forces. The aim of this study is to analyze segmental motion coupling patterns during cervical manual mobilization. METHODS: The position and attitudes of sensors mounted on the atlas and axis were traced in nine embalmed and one fresh human spinal specimen using an electromagnetic tracking system. Segmental bony reference points were registered using a 3D-digitizing stylus for the definition of bone embedded coordinate systems. Segmental motion coupling was recorded for the atlanto-axial joints during manual mobilization through the full range of axial rotation and lateral bending. RESULTS: Coupled motions were described by the direction of the associated motion and by cross-correlation analysis. The results confirm the contra-lateral coupling pattern of axial rotation with lateral bending at C1-C2 observed in previous studies. The cross-correlation analysis offered a more objective interpretation of the coupling pattern for the analysis of the more irregular coupling patterns during lateral bending. Inter-individual differences in coupling patterns were observed. INTERPRETATIONS: The presented method provides possibilities for the study of coupled motion during manual diagnostic and therapeutic practice. Practitioners should be aware of the segmental 3D-aspects of manually induced so called planar mobilizations and their possible influence on motion coupling. Motion coupling patterns may be related to specimen specific anatomy.

3D morphometry of the transverse and alar ligaments in the occipito-atlanto-axial complex: an in vitro analysis.

This study verifies the three-dimensional anatomical features of the transverse and alar ligaments with reference to the axis using a direct in vitro approach. In 20 fresh spine specimens, metal markers were inserted on the cranium, atlas, and axis. After registration of the intact specimen, the bony segments were separated, and markers and anatomical landmarks were digitized. The length and the orientation of the ligaments with reference to the axis were derived from the relative position data. The transverse ligaments of the atlas have a mean estimated length of 21 mm and an absolute angle (i.e., independent of any reference frame) of 119 degrees +/- 17 degrees . The alar ligaments have a mean length of 9 +/- 2.5 mm, and the mean absolute angle between the ligaments is 117 degrees +/- 31 degrees . The plane of the alar ligaments shows a mean backward inclination of -10 degrees +/- 52 degrees . This plane has a mean inclination of 6 degrees +/- 4 degrees with reference to the sagittal plane indicating left-right symmetries. The transverse ligament arches around the dens and demonstrating its function as a stabilizer for the dens as well as guidance for axial rotation movements. A posterior inclination of the alar ligaments may induce a coupled extension in combination with a lateral bending during axial rotation. These detailed aspects of motion steering may be important to consider when attempting to reduce or restore movement.

The influence of circadian rhythm on muscle activity and efficient force production during cycling at different pedal rates.

The aim of this study was to examine the pedal rate and chronobiological impacts on muscle activity pattern and propulsive force production during cycling. Ten male competitive cyclists performed at 06:00 and 18:00 h a submaximal exercise on a cycle ergometer at a power output which elicited 50% of their respective W(max). The exercise was divided into 4 periods lasting 5 min each during which subjects were requested to use different pedal rates (free pedal rate, 70, 90 and 120 rev min-1) in random order. The study demonstrated that, under high pedal rate, several muscles exhibited a phase advance of activity. These modifications of temporal organization of muscle activity were not sufficient to keep an identical propulsive torque pattern. Time to peak torque was delayed when pedal rate increased. The effects of circadian fluctuation on electromyographic activity were limited to a later M. rectus femoris burst end and shorter activity duration for M. tibialis anterior at 06:00 h. From the results of this study, it seems that the influence of pedal rate in the range of torque fluctuation would depend on time-of-day of testing. The decrease in torque fluctuation due to pedal rate increase is reinforced when testing in the early morning. Taking this specific variable into consideration, the chronobiological effect increases the impact of pedal rate variations.

Wrist stabilisation and forearm muscle coactivation during freestyle swimming.

The aim of this study was to evaluate the stabilisation of the wrist joint and the ad hoc wrist muscles activations during the two principal phases of the freestyle stroke. Seven male international swimmers performed a maximal semi-tethered power test. A swimming ergometer fixed on the start area of the pool was used to collect maximal power. The electromyography signal (EMG) of the right flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) was recorded with surface electrodes and processed using the integrated EMG (IEMG). Frontal and sagittal video views were digitised frame by frame to determine the wrist angle in the sagittal plane and the principal phases of the stroke (insweep, outsweep). Important stabilisation of the wrist and high antagonist muscle activity were observed during the insweep phase due to the great mechanical constraints. In outsweep, less stabilisation and lower antagonist activities were noted. Factors affecting coactivations in elementary movements, e.g. intensity and instability of the load, accuracy and economy of the movement were confirmed in complex aquatic movement.

Manual fixation versus locking during upper cervical segmental mobilization. Part 1: an in vitro three-dimensional arthrokinematic analysis of manual flexion-extension mobilization of the atlanto-occipital joint.

BACKGROUND: Segmental manual spinal mobilization techniques are used to restrict the effects of interventions to one spinal segment. It is, however, not known whether it is possible to generate such a localization of effects. Segmental motion in the cervical spine was previously studied by applying pure moments of force on cadaver specimens. So far, no studies have been performed on the segmental three-dimensional (3D)-kinematic aspects of cervical manual flexion-extension mobilization. METHODS: 3D-aspects of manual flexion-extension motion in the atlanto-occipital and atlanto-axial segments were analysed in vitro using an electromagnetic tracking device. Segmental bony reference points were registered using a 3D-digitizing stylus to define bone-embedded coordinate frames. Six spinal specimens--five embalmed and one fresh--were analysed in this study. Segmental motions were analysed in the atlanto-occipital and the atlanto-axial joints during manual mobilization through the full range of flexion-extension mobility. The 3D-kinematic analysis of two different segmental mobilization techniques--manual fixation of C1 versus locking of the inferior cervical spine--is presented. RESULTS: A significant reduction (P<0.05) of the associated axial rotation and lateral bending motions was observed during the manual fixation technique without influencing the main motion component of flexion-extension. The locking technique did not significantly influence the movements on the mobilized atlanto-occipital segment, but reduced all movement components in the atlanto-axial joint. INTERPRETATIONS: The results suggest that, for manual segmental flexion-extension mobilization of the upper cervical spine, manual fixation or locking might be chosen in different situations according to the desired effects.

Manual fixation versus locking during upper cervical segmental mobilization. Part 2: an in vitro three-dimensional arthrokinematic analysis of manual axial rotation and lateral bending mobilization of the atlanto-axial joint.

BACKGROUND: Three-dimensional kinematic aspects of coupled motion during manual cervical mobilization have not previously been studied. Using an in vitro 3D-motion analysis method, the kinematic effects of two different segmental techniques for axial rotation and lateral bending mobilization of the upper cervical spine were investigated as a second part of the study (in part one, kinematic effects of flexion-extension mobilization have been investigated). METHODS: Axial rotation and lateral bending mobilization of the atlanto-occipital and atlanto-axial segments were analysed in vitro using an electromagnetic tracking device. Local reference frames were defined based on bony reference points that were registered using a 3D-digitizing stylus. Five embalmed and one fresh specimen were analysed. Segmental motion was registered simultaneously in the atlanto-occipital and the atlanto-axial joints during manual mobilization through the full range of axial rotation and lateral bending mobility. The 3D-kinematic aspects during regional mobilization were compared with those during segmental mobilization with manual fixation and during segmental mobilization using a locking technique. RESULTS: During both segmental axial rotation techniques of the atlanto-axial joint, a significant reduction of the coupled lateral bending and flexion-extension motion was observed. The locking technique also induced an increase in the main axial rotation component. During lateral bending mobilization of the atlanto-axial joint, the manual fixation technique reduced the effect on the coupled flexion-extension component significantly. INTERPRETATIONS: These results suggest that for manual segmental axial rotation and lateral bending mobilization of the upper cervical spine segmental manual fixation or locking may be preferred in different situations depending on the desired effects. This study brings additional information to the data provided by part 1 of this study on the 3D-arthrokinematic effects of flexion-extension mobilization.

Morphological and constitutional comparison of age-matched in-vivo and post-mortem populations.

Cadaver studies are often used as a reference in clinical studies and in-vivo Body Composition (BC). However, there is a paucity of comparative information between in-vivo and post-mortem populations. Forty living volunteers for the study (18 males and 22 females, age range 55-92 years) were age-matched with a sample of 26 well-preserved cadavers (13 males and 13 females). Twenty eight anthropometric variables were chosen, i.e. nine circumferences, eight breadths, four lengths, five skinfolds, weight and height. These were measured both in vivo and post-mortem. All measures were taken according to Martin and Saller (1957), Clauser et al. (1969) and Clarys et al. (1984). Normality verification, Variant Analysis (one way Anova) and Mollison transformations were used for the comparative treatment. Data from this study confirm that the in-vivo and post mortem macro morphology are in agreement. The best similarities were found between the female groups. This study confirms that cadaver research is reliable for the validation of in-vivo techniques and as a reference standard in the absence of other direct validation measures.

Cadaver studies and their impact on the understanding of human adiposity.

The skinfold thickness is a much-used measurement for monitoring adiposity in a wide range of medical, health, occupational and sport science disciplines. Misconceptions abound, however, in its use, particularly that of purportedly predicting body 'fat' as opposed to 'adipose tissue'. To obtain data to investigate body composition and the extent to which anthropometry can be justifiably used to predict whole-body adiposity, an extensive dissection study was undertaken on 34 cadavers. In addition, to pre-empt questions on the applicability of cadaver data to living subjects, 40 elderly in vivo subjects of the same age range were compared with the cadaver population. No significant macro-morphological differences were found between males or females in the morbid and in vivo groups. Significant findings affect our previous understanding of the predictability of whole-body 'fat'. Skinfold compressibility was by no means constant; skin thickness varied with location in both sexes, females having thinner skin than males; there were significant sex differences in adipose tissue patterning. An identical thickness of adipose tissue did not necessarily contain the same concentrations of fat. Despite this variability, a relationship was demonstrated between aggregate skinfold measures and subcutaneous adipose tissue mass (as opposed to subcutaneous fat), this relationship being more evident in men. A strong relationship was found between subcutaneous adiposity and whole-body adiposity, and between direct skinfold depth measures and whole-body adiposity. The amount of visceral adipose tissue was the same in men and women, but in the men this represented a greater proportion of their total body adiposity. Further, the use of waist-to-hip girth ratio (WHR) was identified as an important predictor of health risk. These findings demonstrate that it is not sustainable to introduce a non-quantifiable error by transforming anthropometric values (skinfolds) into predictions of percentage body fat. If subcutaneous adiposity can be predicted, then an excellent indication of overall adiposity could be obtained. Currently, skinfold measurement can yield a reasonable indication of comparative subcutaneous adiposity (better in men than in women). In neither gender is this prediction completely reliable due to both inter- and intra-individual differences in the skinfold measurement procedure.

Cross-sectional analysis of BMI and some lifestyle variables in Flemish vegetarians compared with non-vegetarians.

Epidemiological studies on vegetarians indicate that appropriately planned vegetarian diets are associated with certain health benefits, which may lower mortality and morbidity. A healthy lifestyle, such as regular physical activity and avoidance of harmful practices, such as smoking and heavy drinking, could also influence these positive health-related outcomes in vegetarians. This study reports BMI, smoking and drinking habits, engagement in physical activity, medication use and subjective health perception in a vegetarian population (women: n = 206, mean age 37.0 +/- 12.3 years; men: n = 120, mean age 42.3 +/- 15.9 years) as compared with a reference Belgian population (women: n = 4993, mean age 49.8 +/- 18.0 years; men: n = 4666, mean age 48.0 +/- 17.1 years). When considering the vegetarian group as a whole, the vegetarians had a lower mean BMI compared with the reference population (respectively 22.1 +/- 3.1 kg/m2 compared with 24.6 +/- 4.8 kg/m2 for women (p < 0.001) and respectively 22.6 +/- 3.6 kg/m2 compared with 25.7 +/- 4.0 kg/m2 for men (p < 0.001)). Vegetarians smoked less than subjects of the reference group (13.5% compared with 28.5% respectively; p < 0.001). During weekdays the percentage of subjects consuming alcoholic drinks in the two populations was comparable (32.8 in the vegetarian and 35.8 in the reference population; p = 0.159). During the weekend, more subjects of the reference population drank alcohol compared with the vegetarian subjects (70.2% vs. 58.6% respectively; p = 0.026). More vegetarians were involved in intensive physical activity (over 4 h per week) compared with the reference population (36.8% vs. 17.3% respectively; p < 0.001), while fewer vegetarians were involved in moderate physical activity (up to 4 h per week) compared with subjects of the reference group (28.2% and 51.0% respectively; p < 0.001). Percentages of subjects involved in no physical activity were comparable in both groups (vegetarians 34.9 vs. reference subjects 31.8; p = 0.625). Use of prescribed medication was lower among the vegetarians (25.5% compared with 47.3% in the reference population; p < 0.001), while use of non-prescribed drugs was comparable between both groups (34.1% in the vegetarian group and 28.2% in the reference group; p = 0.580). More vegetarian subjects perceived their health to be good to very good compared with the subjects of the reference population (90.4% vs. 77.2% respectively; p < 0.001). The significant difference for the BMI values when comparing the vegetarian males and females with the reference population cannot be completely explained by the evaluated lifestyle characteristics. However, the lower BMI values in vegetarians are in agreement with the literature.

Measurement of three-dimensional intra-articular kinematics: methodological and interpretation problems.

Intra-articular kinematics evaluates joint motion in terms of the configuration of the joint. Therefore data are needed concerning joint kinematics as well as joint configuration. We have developed accurate measurement methods for both in vivo and in vitro evaluation. Interpretation of the processed data is more complex than simply setting up a coordinate system based on the joint configuration. Although the description of intra-articular motion in terms of Euler-Cardan or helical angles may be complete, the therapeutic interpretation may be doubtful. Using the the ulno-humeral joint during flexion-extension as an example, we found the combination of helical angles in the directions of extension/external rotation/varus. In the case of the Cardan angles, inconsistent patterns of rotation resulted from a different choice of sequence order and were different from the helical angles. The finite helical axis (FHA) provides a functional representation of the joint movement, i.e. pathways of motion, whereas the sequence dependency of Euler-Cardan angles produces problems in the therapeutic interpretation of the movement. Therefore we believe that an FHA approach should be used in intra-articular kinematics research.

Effects of spontaneously chosen crank rate variations on electromyographic responses in sub-maximal arm exercise in inexperienced subjects.

The aim of the present study was to compare electromyographic responses during arm exercises with a crank rate chosen spontaneously ( T(S)) or set at 20% below or above ( T(-20), T(+20)) the spontaneously chosen crank rate (SCCR). Ten male physical education students performed arm exercises with intensities ranging from 20% to 80% of maximal power. Muscular activity levels were analysed for the biceps brachii and the triceps brachii muscles using integrated rectified surface electromyography (iEMG). All values were presented as the mean and standard deviation. During T(S), the sum of iEMG for the two muscles studied was significantly ( P<0.05) lower than during T(+20) for each power output. No significant differences were observed in iEMG values between T(S) and T(-20). The hypothesis that SCCR relates to a minimisation of muscle activation during an upper body exercise was not confirmed. Variations superior or inferior to a 20% increase of the iEMG responses do not influence it. Moreover, the selection of crank rates depends on the power output and the SCCR increased significantly ( P<0.05) with increasing power output.