Karin Henriksson-Larsén

Muscle performance, electromyography and fibre type composition in fibromyalgia and work-related Myalgia

Muscle performance and fibre type composition were investigated in women with fibromyalgia, work-related trapezius myalgia and healthy volunteers. Each subject performed 100 repetitive shoulder flexions using an isokinetic dynamometer during simultaneous registration of surface electromyography. A biopsy from the trapezius muscle was obtained. The groups differed neither in mechanical performance nor in fibre type proportions. An inability to relax between contractions was found in all registered muscles in patients with fibromyalgia. The patients with work-related myalgia displayed an inability to relax only in the myalgic trapezius muscle. An inability to relax during repetitive movements might play an important role both in initiating and upholding muscle pain.

Effect of High Impact Activity on Bone Mass and Size in Adolescent Females: A Comparative Study Between Two Different Types of Sports

The purpose of this cross-sectional study was to investigate the influence of two different types of weight-bearing activity, muscle strength, and body composition on bone mineral density (BMD), bone mineral content (BMC), and bone area in three different groups of late adolescent girls. The first group consisted of 10 females participating in competitive rope-skipping (age 17.8 ± 0.8 years) training for 6.7 ± 3.1 hours/week; the second group consisted of 15 soccer players (age 17.4 ± 0.8 years) training for 6.1 ± 2.0 hours/week; and the third group consisted of 25 controls (age 17.6 ± 0.8 years) with physical activity of 0.9 ± 1.1 hours/week. The groups were matched for age, height, and weight. BMD (g/cm2), BMC (g), and bone area (cm2) of the total body, lumbar spine, hip, total femur, distal femur, diaphyses of femur and tibia, proximal tibia, and humerus were measured using dual-energy X-ray absorptiometry (DXA). Bone density was also assessed in the radial forearm site of the dominant limb in the rope skippers and in 10 matched controls. The rope skippers had 22% higher BMD at the ultradistal site (P < 0.01). Both high-activity groups had significantly higher BMD (P < 0.05) at most loaded sites compared with the control group. When adjusting for differences in lean mass and starting age of sport-specific training between the activity groups, the rope-skipping group had a higher BMD of the total body, lumbar spine, and right humerus compared with the soccer group. They also had a significantly higher bone area of the total body, total femur, and the proximal femur than both other groups, and a significantly higher bone area of the tibia diaphysis, compared with the soccer group. In a multivariate analysis among all subjects (n = 50), all BMD sites, except the femur diaphysis, distal femur, and proximal tibia, were significantly related to type of physical activity (β= 0.25–0.43, P < 0.05). The bone area values at different sites were strongly related to muscle strength and parameters related to body size [height, weight, lean mass, fat mass, and body mass index (BMI)]. In conclusion, it appears that in late adolescent women, weight-bearing activities are an important determinant for bone density, and high impact activities such as jumping also seem to be associated with a modification of the bone geometry (hence, the bone width) at the loaded sites.

Cardiac autonomic imbalance in an overtrained athlete

PURPOSE In order to investigate overtraining-related adaptations in the autonomic nervous system, cardiac autonomic activity was examined in a junior cross-country skier who presented with reduced performance in competitions, early breathlessness during training sessions, and accumulated central fatigue. METHODS Power spectral analysis of heart rate variability (HRV) was performed before, when overtrained (OT), and after recovery (Rec). RESULTS In the overtrained state, high frequency (HF) and total powers in the lying position were higher compared with before and after. In normalized units, the increased HF in OT was even more prominent and clearly higher than in any control subject, and it was reversed in Rec. Resting heart rate was slightly reduced in OT and returned to baseline in Rec. CONCLUSIONS The shift toward increased heart rate variability, particularly in the HF range, together with a reduced resting heart rate suggest a cardiac autonomic imbalance with extensive parasympathetic modulation in this athlete when overtrained.

Distribution of different fibre types in human skeletal muscles. I. Method for the preparation and analysis of cross-sections of whole tibialis anterior

SummaryThe aim of this study was to examine whether small biopsy specimens are representative of the whole human skeletal muscle or whether the different fibre types are unevenly distributed at different depths of the muscle. Ten micrometre thick cross-sections of whole human tibialis anterior were prepared using LKB PMV Cryo-Microtomes with a stroke length of 160 to 480 mm and the sections were stained for myofibrillar ATPase according to a modified procedure. The total and relative number of different fibres (Types 1 and 2) was determined in every 9th mm2 of the section. The data obtained were analysed by means of a computer program, which allowed assessment of bivariate data in the form of contour plots.The total number of fibres varied greatly between individuals (from 96 000 to 162 000; five individuals). The relative number of different fibres varied systematically in all individuals as a function of depth in the muscle. There was a gradual, often dramatic, relative increase in Type 2 fibre occurrence from the surface of the muscle (about 10–25%) towards the deeper regions (30–50%), the maximum being approximately along a line slightly posterior to the middle of the muscle. Additionally, superficial peaks were seen in places. In conclusion, the fibre type distribution in the tibialis anterior is not random. These results point to the importance of defining biopsy depth.

Physical training with and without oxygen in patients with chronic obstructive pulmonary disease and exercise-induced hypoxaemia

A randomized, controlled, single-blind study was performed on 20 patients with chronic obstructive pulmonary disease and exercise-induced hypoxaemia. Ten patients each were randomly assigned to one of two groups, one training with air and the other training with oxygen. There were no significant differences between the groups regarding values measured prior to the study. The patients trained 3 times per week for 30 minutes each time for a duration of 8 weeks. The training consisted of interval walking on a treadmill (intensity set according to Borg ratings) with either air or oxygen administered through a nasal cannula at a rate of 5 l/min. Training significantly improved the 6-minute walking distance by 20% and 14% in the air and oxygen group, respectively, when the patients were tested on air. In the same test the air group significantly decreased Borg ratings for perceived exertion. Borg ratings for dyspnoea and perceived exertion significantly decreased in the oxygen group when they were tested on oxygen. It was concluded that oxygen supplementation did not further improve the training effect, compared with training with air, in patients with chronic obstructive pulmonary disease and exercise-induced hypoxaemia.

Heart rate variability in athletes : relationship with central and peripheral performance.

PURPOSE To investigate relationships between heart rate variability (HRV) and peripheral and central performance measures, 17 cross-country (X-C) skiers and seven canoeists were studied before and after a training period of 7 months. METHODS For the skiers and canoeists respectively, leg and arm peak torque (Tq), time to peak torque (TiTq), and total work (Wrk) were measured in an isokinetic dynamometer. Maximal oxygen uptakes (VO(2max)) were obtained from treadmill tests. Power spectral analysis of HRV was performed on electrocardiographic recordings in the resting supine position and after a tilt to yield power in the low-frequency (0.04--0.15 Hz) and high-frequency (0.15--0.45 Hz) components of HRV. RESULTS The change in normalized LF-variability in standing (Delta LFnT) correlated (P < 0.01) with the changes in TiTq (r = 0.63), max lactate (r = -0.63), and VO(2max) (r = -0.53). The change in absolute LFT was inversely correlated with the change in Tq. Subjects who improved VO(2max) were characterized by consistently higher high-frequency and total HRV than subjects with deteriorated aerobic capacity (P < 0.05). CONCLUSION The results suggest that improved measures of both peripheral and central (aerobic) work capacities were associated with a reduction of low-frequency HRV in the tilted position. High-frequency and total HRV did not change in proportion with changes in muscle performance or aerobic capacity, but the ability to further improve VO(2max) with training in these already fit subjects seemed to depend on their average levels of these HRV measures, interpreted to reflect parasympathetic activity.

Low Bone Mass Density at Multiple Skeletal Sites, Including the Appendicular Skeleton in Amenorrheic Runners

Abstract. The aim of this study was to investigate any difference in bone mass at different sites between female long-distance runners with amenorrhea and those with eumenorrhea. We compared 10 amenorrheic and 10 eumenorrheic athletes to determine whether athletes with amenorrhea have lower BMD in multiple skeletal regions, including weight-bearing lower limbs. The amenorrheic group had experienced menstrual dysfunction ranging from 3 to 43 months. As a further control group, 16 eumenorrheic soccer players were compared with the former two running groups regarding their BMD measurements. The two groups were matched for age, height, and amount of training. Areal bone mineral density (BMD) was measured and was found to be significantly lower in the total body, humerus, spine, lumbar spine, pelvis, femoral neck, trochanter, total femur, femur diaphysis, tibia diaphysis and in the nonweight-bearing head of the femur in the amenorrheic group. Body weight, BMI, fat mass, and body fat percent were significantly lower in the amenorrheic group. The differences in the BMD of the head, humerus, femoral neck, total femur, femur diaphysis, and tibia diaphysis disappeared when adjusted for body weight. Compared with the soccer group, the amenorrheic subjects had significantly lower BMD values at all sites except for the head, Wards triangle, and femur diaphysis. Blood samples were obtained in the two running groups for analysis of osteocalcin, carboxy terminal telopeptide (ICTP), procollagen I (PICP), and estradiol. There were no significant differences between the groups but there was a strong tendency towards a lower estradiol level and a higher osteocalcin level in the amenorrheic group. A free estradiol index (FE2) was derived as the ratio of estradiol to sex hormone binding globulin (SHBG) and was significantly lower in the amenorrheic group. No difference in their daily intake of total energy, protein, carbohydrates, fiber, calcium, and vitamin D was observed. However, both groups showed a surprisingly low energy intake in relation to their training regimens. Stepwise regression analyses revealed that weight was the best predictor of spine BMD in both groups. Estradiol and FE2 were significant predictors of the BMD of the proximal femur in the eumenorrheic group, but did not predict any BMD site in the amenorrheic group. In conclusion, amenorrhea in athletic women affects trabecular and cortical bone in both axial and appendicular skeleton. However, some of the discrepancy can be explained by a lower body weight. Physical weight-bearing activity does not seem to completely compensate for the side effects of reduced estrogen levels even in weight-bearing bones in the lower extremity and spine.

Fibre Loss and Distribution in Skeletal Muscle from Patients with Severe Peripheral Arterial Insufficiency

Cross-sections of whole calf muscles (m soleus and m gastrocnemius) were obtained from five previously clinically health individuals who had died accidentally (controls) and from amputated legs of five patients of similar age with severe peripheral arterial insufficiency. In the controls, but not in the patients, a characteristic distribution of different fibre types over the entire cross-sections was found, with a relative increase in number of (slow twitch) type 1 fibres in the central parts of both m soleus and m gastrocnemius. A pronounced neuromuscular pathomorphology was found in the patients, especially in m gastrocnemius. The findings suggested widespread damage to the fibres. There was also a lower total number of fibres in these ischaemic muscles; about 50% of the fibres of m gastrocnemius seemed to have disappeared. The results suggested that the relative inactivity as such may be responsible for some of the structural changes, above all the dedifferentiated distribution of different fibres over the cross-section. However, repeated acute and chronic subacute ischaemia may also cause, in the long term, irreparable damage and loss of many individual fibres. This may explain why muscles of patients with peripheral arterial insufficiency are also weaker, during single contractions. The lack of corresponding muscular atrophy in these patients seems to a large extent to be explained by an increase in connective tissue.

Physiological predictors of performance in cross-country skiing from treadmill tests in male and female subjects.

In order to study which parameter that best corresponds to performance during cross‐country skiing, seven male and nine female cross‐country skiers were tested with treadmill tests. Parameters measured or computed by metabolic gas measurements were the anaerobic threshold (AT), threshold of decompensated metabolic acidosis (TDMA), the exercise intensity where the Respiratory exchange ratio reaches 1.0 (R = 1) and peak oxygen (O2) uptake (VO2peak). Onset of blood lactate accumulation (OBLA, 4 mmol·l−1 blood lactate) was also measured. The various parameters were measured in percentage of maximal heart rate, percentage of peak O2 uptake, VO2 ml·kg−1·min−1, VO2 ml·min−1·kg−2/3 and VO2 l·min−1. Results from four large competitions were also collected to rank the subjects. With correlation analysis, it was revealed that in male subjects a high OBLA was associated with good ranking results (r = (−0.829) − (−0.964); P < 0.05–0.001). In female subjects, the best association with competition results was found for R = 1 (r = (−0.715) − (−0.810); P < 0.05). Concerning VO2 measurements, for male subjects the unit l·min−1 is suggested to be used and for female subjects either the units l·min−1, ml·min−1·kg−2/3, or ml·kg−1·min−1 could be used when predicting performance in cross‐country skiing. In conclusion, treadmill tests can be used for the prediction of performance in cross‐country skiing. Further, various parameters from treadmill tests in men and women are best used as predictors of performance in cross‐country skiing.

Combined metabolic gas analyser and dGPS analysis of performance in cross-country skiing

The purpose of this study was to provide a more detailed analysis of performance in cross-country skiing by combining findings from a differential global positioning system (dGPS), metabolic gas measurements, speed in different sections of a ski-course and treadmill threshold data. Ten male skiers participated in a freestyle skiing field test (5.6 km), which was performed with dGPS and metabolic gas measurements. A treadmill running threshold test was also performed and the following parameters were derived: anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio  =  1, onset of blood lactate accumulation and peak oxygen uptake ([Vdot]O2peak). The combined dGPS and metabolic gas measurements made detailed analysis of performance possible. The strongest correlations between the treadmill data and final skiing field test time were for [Vdot]O2peak (l · min−1), respiratory exchange ratio  =  1 (l · min−1) and onset of blood lactate accumulation (l · min−1) (r  =  −0.644 to − 0.750). However, all treadmill test data displayed stronger associations with speed in different stretches of the course than with final time, which stresses the value of a detailed analysis of performance in cross-country skiing. Mean oxygen uptake ([Vdot]O2) in a particular stretch in relation to speed in the same stretch displayed its strongest correlation coefficients in most stretches when [Vdot]O2 was presented in units litres per minute, rather than when [Vdot]O2 was normalized to body mass (ml · kg−1 · min−1 and ml · min−1 · kg−2/3). This suggests that heavy cross-country skiers have an advantage over their lighter counterparts. In one steep uphill stretch, however, [Vdot]O2 (ml · min−1 · kg−2/3) displayed the strongest association with speed, suggesting that in steep uphill sections light skiers could have an advantage over heavier skiers.