Effect of endurance training on muscle fiber type composition and capillary supply in rat diaphragm

Summary Muscle fiber type composition and capillary supply in rat diaphragm were investigated after 14 weeks of endurance training: body weight and muscle fiber area were significantly decreased, the muscle fiber type composition, capillary to fiber ratio and number of capillaries around each fiber type were unchanged, and the capillary density and number of capillaries around each fiber relative to fiber type areas were significantly increased. These small fiber areas and increased capillary supplies in the trained rats would facilitate oxygen transport to all parts of the muscle fiber during exercise. It is concluded that the changes observed in the trained rat diaphragm appear to enhance the capacity for oxidative metabolism.     

Changes in performance,maximal oxygen uptake and maximal accumulated oxygen deficit after 5, 10 and 15 days of live high:train low altitude exposure

Nineteen well-trained cyclists (14 males and 5 females, mean initial V˙O_2max 62.3 ml kg^–1 min^–1) completed a multistage cycle ergometer test to determine maximal mean power output in 4 min (MMPO_4min), maximal oxygen uptake (V˙O_2max) and maximal accumulated oxygen deficit (MAOD). The athletes were divided into three groups, each of which completed 5, 10 or 15 days of both a control condition (C) and live high:train low altitude exposure (LHTL). The C groups lived and trained at the ambient altitude of 610 m. The LHTL groups spent 8–10 h night^–1 in normobaric hypoxia at a simulated altitude of 2,650 m, and trained at the ambient altitude of 610 m. The changes to MMPO_4min, V˙O_2max and MAOD in response to LHTL altitude exposure were not significantly different for the 5-, 10- and 15-day treatment periods. For the pooled data from all three treatment periods, there were significant increases in MMPO_4min [mean (SD) 5.15 (0.83) W kg^–1 vs 5.34 (0.78) W kg^–1] and MAOD [50.1 (14.2) ml kg^–1 vs 54.9 (13.1) ml kg^–1] in the LHTL athletes between pre- and post-altitude exposure. There were no significant changes in MMPO_4min [5.09 (0.76) W kg^–1 vs 5.16 (0.86) W kg^–1] or MAOD [50.5 (14.1) ml kg^–1 vs 49.1 (13.0) ml kg^–1] in the C athletes over the corresponding period. There were significant increases in V˙O_2max in the athletes during both the LHTL [63.2 (9.0) ml kg^–1 min^–1 vs 64.1 (9.0) ml kg^–1 min^–1] and C [62.0 (8.6) ml kg^–1 min^–1 vs 63.4 (9.2) ml kg^–1 min^–1] conditions. In these athletes, there was no difference in the impact of 5, 10 or 15 days of LHTL on the increases observed in MMPO_4min, V˙O_2max or MAOD; and LHTL increased MMPO_4min and MAOD more than training at low altitude alone. Electronic Publication     

The Effects of Discrimination Training on Voluntary Control of Cephalic Vasomotor Activity

The present study was conducted to test Brener's calibration theory of visceral learning. It was hypothesized that training in discrimination of cephalic vasomotor responses would enhance acquisition of voluntary and biofeedback control of cephalic vasomotor response. Four groups were given discrimination training to detect either constriction, dilation, both constriction and dilation, or given false feedback. All groups were then given biofeedback training in constriction. All groups were assessed on discrimination accuracy, acquisition of biofeedback control of constriction, and voluntary control of dilation and constriction. The results indicated that discrimination of cephalic vasomotor responses can be learned and that this skill facilitates the acquisition of biofeedback and voluntary control of vasomotor responses. This facilitation occurs only if discrimination training is given for the specific response to be learned. The data suggest that discrimination of the relevant response is a necessary but not sufficient condition for acquisition of voluntary control in biofeedback learning.     

Laboratory compliance with federal government and professional society recommendations

Quality assurance issues have assumed growing importance in the cytology laboratory. The 1988 Clinical Laboratories Improvement Amendment (CLIA '88) (United States Department of Health and Human Services, Federal Register: U.S. Government Printing Office 1990;55:9495) regulates the patient identifiers and clinical data on the requisition form but does not mandate physician compliance to provide the information. We investigated the use of patient identifiers and clinical data by laboratories as specimen acceptance/rejection criteria. We surveyed 81 board certified cytopathologists and 235 randomly selected cytology laboratories for acceptance criteria of cytology specimens and received responses from 104. Approximately two thirds of all responding laboratories had specific criteria for rejecting specimens on the basis of inadequate identification or clinical data. While the vast majority required the specimens to be identified with patient name, collection date, and specimen source, a minority of laboratories required clinical information such as LMP, prior atypical cytologic/histologic specimens, and history of previous therapy. Little correlation was found between practice setting and the use of rejection criteria. Diagn Cytopathol 1994; 11:85–92. © 1994 Wiley-Liss, Inc.     

Age- and training-related changes in the collagen metabolism of rat skeletal muscle

Summary The effects of ageing and life-long endurance training on the collagen metabolism of skeletal muscle were evaluated in a longitudinal study. Wistar rats performed treadmill running 5 days a week for 2 years. The activities of collagen biosynthesis enzymes, prolyl-4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, were highest in the muscles of the youngest animals, decreased up to the age of 2 months and from then on remained virtually unchanged. The enzyme activity in young animals was higher in the slow collagenous soleus muscle than in the rectus femoris muscle. The enzyme activity in the soleus muscle was higher for older trained rats than older untrained rats. The relative proportion of type I collagen increased and that of type III collagen decreased with age, suggesting a more marked contribution by type I collagen to the agerelated accumulation of total muscular collagen. The results show that collagen biosynthesis decreases with maturation and that life-long endurance training maintains a higher level of biosynthesis in slow muscles.     

Alteration of regulatory enzyme activities in fast-twitch and slow-twitch muscles and muscle fibres in low-intensity endurance-trained rats

The effect of progressive, low-intensity endurance training on regulatory enzyme activities in slow-twitch (ST) and fast-twitch (FT) muscle fibres was studied in 32 rats. Of those rats 16 were trained on a treadmill at a running speed of 10m · min^–1 5 days a week over an 8-week period. Running time was progressively increased from 15 min to 2 h · day^–1. Of the rats 4 trained and 4 sedentary rats were also subjected to acute exhausting exercise. Enzyme activities of phosphofructokinase 1 (PFKI) from glycolysis, -ketoglutarate dehydrogenase (-KGDH) from the Krebs cycle and carnitine palmitoyltransferase (CPT I and II) from fatty acid metabolism in soleus, tibialis anterior and gastrocnemius muscles were measured in trained and sedentary rats. Enzyme activities of individual ST and FT fibres were measured from the freeze-dried gastrocnemius muscle of 8 trained and 8 sedentary rats. In the sedentary rats the activity of PFK1 in tibialis anterior and soleus muscles was 141% and 41% of the activity in gastrocnemius muscle, respectively. The activity of -KGDH in tibialis anterior and soleus muscles was 164% and 278% of the activity in gastrocnemius muscle, respectively. The activity of CPT I in tibialis anterior and gastrocnemius muscles were at the same level, but in soleus muscle the activity was 127% of that in mixed muscle. Endurance training increased enzyme activities of -KGDH and CPT I significantly (P < 0.05) in gastrocnemius muscle but not in soleus or tibialis anterior muscle. After training both -KGDH and CPT II activities were elevated significantly (P < 0.05) in the ST fibres of gastrocnemius muscle, whereas in FT fibres only -KGDH was increased. For PFK1 activity no significant change was observed in ST or FT fibres. After acute exercise, activities of mitochondrial enzymes -KGDH and CPT I tended to be elevated in all muscles. Thus, low-intensity endurance training induced significant peripheral changes in regulatory enzyme activities in oxidative and fatty acid metabolism in individual ST or FT muscle fibres.     

Standard skin prick testing and sensitization to inhalant allergens across Europe--a survey from the GALEN network

Skin prick testing (SPT) is the standard method for diagnosing allergic sensitization but is to some extent performed differently in clinical centres across Europe. There would be advantages in harmonizing the standard panels of allergens used in different European countries, both for clinical purposes and for research, especially with increasing mobility within Europe and current trends in botany and agriculture. As well as improving diagnostic accuracy, this would allow better comparison of research findings in European allergy centres. We have compared the different SPT procedures operating in 29 allergy centres within the Global Allergy and Asthma European Network (GA(2)LEN). Standard SPT is performed similarly in all centres, e.g. using commercial extracts, evaluation after 15-20 min exposure with positive results defined as a wheal >3 mm diameter. The perennial allergens included in the standard SPT panel of inhalant allergens are largely similar (e.g. cat: pricked in all centres; dog: 26 of 29 centres and Dermatophagoides pteronyssinus: 28 of 29 centres) but the choice of pollen allergens vary considerably, reflecting different exposure and sensitization rates for regional inhalant allergens. This overview may serve as reference for the practising doctor and suggests a GA(2)LEN Pan-European core SPT panel.     

Influence of plyometric training on the mechanical impedance of the human ankle joint

The objective of this work was to study the effects of plyometric training on the mechanical properties of the ankle joint in humans. Changes in the mechanical parameters of this musculo-articular structure were quantified with the aid of a sinusoidal perturbation technique. This technique allowed the expression of the mechanical impedance of the musculo-articular system in terms of stiffness, viscosity and inertia. Measurements were performed under passive conditions and when the subject performed plantar flexion. A 7-week period of training induced a decrease in the slope of the relationship between stiffness and plantar flexion torque, whereas passive stiffness was increased. A slight decrease in viscosity and an invariability in inertia were also found. These results are interpreted in terms of the possible adaptations of the musculo-articular structure and ultrastructure involved in the performance of plantar flexion. Accepted: 11 April 1997     

Changes in isometric force- and relaxation-time,electromyographic and muscle fibre characteristics of human skeletal muscle during strength training and detraining

HÄKKINEN, K., ALÉN, M. & KOMI, P.V. 1985. Changes in isometric force- and relaxation-time, electromyographic and muscle fibre characteristics of human skeletal muscle during strength training and detraining. Acta Physiol Scand 125, 573–585. Received 26 January 1985, accepted 9 May 1985. ISSN 0001–6772. Department of Biology of Physical Activity and Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland. Eleven male subjects (20–32 years) accustomed to strength training went through progressive, high-load strength training for 24 weeks with intensities ranging variably between 70 and 120% during each month. This training was also followed by a 12-week detraining period. An increase of 26.8% (P < 0.001) in maximal isometric strength took place during the training. The increase in strength correlated (P < 0.05) with significant (P < 0.05–0.01) increases in the neural activation (IEMG) of the leg extensor muscles during the most intensive training months. During the lower-intensity training, maximum IEMG decreased (P < 0.05). Enlargements of muscle-fibre areas, especially of fast-twitch type (P < 0.001), took place during the first 12 weeks of training. No hypertrophic changes were noted during the latter half of training. After initial improvements (P < 0.05) no changes or even slight worsening were noted in selected force-time parameters during later strength training. During detraining a great (P < 0.01) decrease in maximal strength was correlated (P < 0.05) with the decrease (P < 0.05) in the maximum IEMGs of the leg extensors. This period resulted also in decreases (P < 0.05) of the mean muscle-fibre areas of both fibre types. It was concluded that improvement in strength may be accounted for by neural factors during the course of very intensive strength training. Selective training-induced hypertrophy also contributed to strength development but muscle hypertrophy may have some limitations during long-lasting strength training, especially in highly trained subjects.     

Correlation between percentage fiber type area and myosin heavy chain content in human skeletal muscle

Histochemical methods are routinely used to delineate skeletal muscle fiber types. In the present investigation, this qualitative determination of fiber type composition was compared to the electrophoretically determined myosin heavy chain (MHC) content from a large number of human muscle biopsy samples. Biopsies were taken from the vastus lateralis muscle at the beginning and every 2 weeks during 8 weeks of highi-ntensity resistance training from men (n = 13) and woman (n = 8). Muscle was also extracted from nontraining men (n = 7) and women (n = 5) at the same periods. Six muscle fiber types (I, IC, IIAC, IIA, IIAB, and IIB) were determined using basic myofibrillar adenosine triphosphatase histochemistry. Cross-sectional areas were determined for the three major fiber types (I, IIA, and IIB) and used to calculate the percentage area of these types. Electrophoretic techniques were used to separate and quantify the percentage MHC content in these same biopsy samples, and these data were then used to compare with the percentage fiber type area. Correlation analyses suggest a relationship between the histochemically assessed percentage fiber type area and the electrophoretically assessed MHC content in human limb musculature. However, because of possible histochemical misclassification of some fibers (especially in trained muscle) both techniques may be essential in yielding important information about fiber type composition and possible fiber type transformations.