Exercise-induced muscle soreness is characterized by stiffness, tenderness and pain during active movements and weakness of the affected musculature the days after unusually or particularly heavy work. The most pronounced subjective symptoms do not arise immediately but rather between a couple of hours to some days after the exercise (a delayed-onset of muscle soreness), the intensity of pain is greatest about 48 hours after the work. A particular association exists between muscle soreness and eccentric contractions. Despite the fact that muscle soreness is a well known phenomenon in the sphere of sports as well as working life, the pathophysiological mechanisms underlying this are still not understood. In the present study a detailed analysis of human muscle fibre population structure after high tension work (eccentric exercise) that gave rise to muscle soreness, was carried out. The objective was to elucidate how fibres of different types are influenced by repeated muscle contractions reaching extreme tension levels using qualitative and quantitative light and electron microscopic techniques. It was hoped that such morphological analysis would provide a basis for discussion of possible causes for muscle soreness. The muscle function after the work was measured by isokinetic methods. To improve the basis for the ultrastructural analysis the fibre populations in untrained and en­durance trained human m. vastus lateralis of age-matched individuals were classified into different fibre type groups according to their ultrastructure. The selective glycogen depletion from Type 1 fibres seen after long term submaximal work, visualized electron microscopically with PA-TSC-SP staining, substantiated the usefulness of the appearance of the M-band to differentiate between fibre types. Stereological data showed that neither volume density of mitochondria nor of lipid droplets provide sufficient criteria to differentiate between fibre types. After an eccentric exercise regimen sore muscles (m. soleus or m. vastus lateralis) showed disturb­ances of the cross striated band pattern. Fibres with disorganized myofibrillar material made up 1/3, 1/2 and 1/10 of the analysed material, 1 hour, 3 and 6 days after exercise, respectively. The myofibril­lar lesions were preferably localized in the Z-band. This showed streaming, broadening and sometimes total disruption. The Type 2 fibres were most affected. The reduction of strength was greatest with the most rapid contractions. Strength remained de­creased the period when the structural damage was most pronounced. Eight weeks of eccentric muscle training reduced all the above negative effects. The results indicate that the Z-disc constitute the weak link in the myofibrillar contractile chain at high muscle tensions. It is suggested that the myofibrillar lesions are a direct result of mechanical tearing. Rupture of myofibrils is thought to result in formation of protein components and a con- sequental release of protein bound ions that via osmosis result in oedema and soreness. Training, using eccentric contractions over a long period of time leads to adaptations at the fibre level by a reorgani­zation of the contractile apparatus as well as an optimization of nervous coordination. / <p>S. 1-40: sammanfattning, s. 41-79: 5 uppsatser</p> / digitalisering@umu

Patients with Peripheral Arterial Disease have a reduced capacity for exercise, the exact causes of which are poorly understood. This thesis investigated alternative testing procedures that aim to provide a more complete and precise description of the exercise capacities of these patients. Furthermore, the potential roles of gastrocnemius muscle fibre morphometry, capillary supply and glycogen stores in the exercise tolerance of PAD patients were studied. Study one aimed to determine the effect of test repetition on maximal exercise performance and test-to-test variability in PAD patients using an incremental treadmill walking test (T) (n=5), an incremental cycle test (C) (n=5), and incremental endurance (PF-endurance) and maximal strength (PF-strength) plantar flexion tests (n=5). Tests were conducted once per week for eight weeks. Performance was stable on the T (~530 s) and C (~500 s) tests across the eight weeks. Test-to-test variance on T decreased from 16%CV (CV: coefficient of variation) to 6%CV (p=.21,NS), and from ~8%CV to 2%CV on C (p<.05) over the eight week period. Variance of peak gas exchange variables tended to decrease with performance variance on both tests; however, other physiological variables, and the associated variance levels, were stable throughout the study. PF strength (635-712N) gradually increased over the initial 2-3 weeks (p<.05) which was accompanied by a reduction in variance from ~8%CV to ~3%CV (p<.05). Similarly, PF endurance increased over the first two weeks (~32,000 to 41500 N.s-1) while variance of this measure fell from ~21%CV to ~10%CV (p<.05) over the study duration. It is concluded that the implementation of familiarisation sessions leads to a reduction in whole body and local calf muscular performance variance in patients with PAD. Using a randomised crossover design, study two aimed to compare performance and the physiological and symptomatic responses between a T test and a C test in 16 patients with PAD. Peak exercise time on C (690 s) was greater than that on T (495 s); however the two were significantly correlated (n=16, r=.69, p<.05). Peak HR (120 bpm), VO2 (~1.22 l.min-1) and rate pressure product (~20') did not differ between the two tests, nor did the post exercise ankle pressure (T: 56; C: 61 mmHg). In two subjects with lower back pain during C, the ankle pressure of their "worst" limbs failed to fall by >10mmHg. Performance on both the T and C tests was closely related to the onset of leg symptoms; however the site of pain during C was much more variable than during T. Incremental cycle testing would overcome some of the limitations of treadmill testing (e.g. measurement of mechanical work), and it appears to be an acceptable alternative for measuring the exercise capacity and physiological exercise responses in known claudicants. Use of cycle ergometry for the diagnosis of PAD requires testing in the general population. Study three aimed to compare whole body (T test and C test) and local calf muscular (PF strength and endurance) exercise performance between 16 PAD patients (age: 63 ± 2; BMI: 25.9 ± 1.1) and 13 healthy, sedentary control (CON) subjects (age: 62 ± 1; BMI: 25.9 ± 0.4), and to describe relationships between the whole body and local calf muscular exercise capacities within the two groups. Furthermore, this study aimed to compare several histochemical characteristics of the medial gastrocnemius muscle fibres between PAD and CON, and to establish whether these factors were related to the exercise capacities of both groups. Maximal performance on T was 59% lower in the PAD group compared with the CON group, as was performance on C (50%), PF strength (25%), and PF endurance (58%). Compared with CON, PAD patients had a lower estimated calf muscle mass and a slight reduction (10%) in muscle fibre size (p=.14, NS). They also had a lower proportion of type I fibres (PAD: 49%; CON: 62%) that was offset by a greater proportion of type IIA fibres (PAD: 27%; CON: 16%), and a reduction in the capillary contacts per muscle fibre (PAD: 1.63; CON: 2.12) compared with CON. When expressed relative to fibre area there were no differences in capillarisation between PAD and CON; however this index was significantly related to resting and post exercise ABI in the PAD patients. There were no differences in the mixed muscle [glycogen], nor the optical density of glycogen in the individual fibres, between the two groups. PF endurance was poorly predictive of walking performance, and did not correlate with any of the morphological variables in both groups. Calf muscle mass correlated with PF strength (r=.59 - .62), and strength was correlated with T performance (r= .61 - .63) in both groups. In the PAD patients, T performance was correlated with the cross sectional area (n=12, r=.72, p<.05), capillary contacts (n=10, r=.81, p<.05) and glycogen density (n=9, r=.81, p<.05) of type I fibres. This study confirms that a reduction in calf strength, which appears to be mediated through muscle atrophy, plays some role in the reduced exercise capacity of claudicants. While both fibre area and capillary supply seem to be of relevance to the exercise capacity of PAD patients, these two factors are closely linked and further research is required to establish the determinants, and relative importance of both. An important, and possibly limiting role of carbohydrate oxidisation in PAD patients is supported by the strong relationship between type I glycogen stores and whole body exercise capacity.

Abstract The dihydropyridine receptor (DHPR) in the skeletal muscle plasma membrane functions as a voltage sensor for excitation-contraction coupling. In the present work the expression and special features of DHPR were studied under various conditions. In order to localize and visualize the DHPRs, a method using fluorophore-conjugated dihydropyridine molecules as a probe was developed. In addition, different laboratory assays and electrophysiological measurements were used to study the expression of the myofibrillar proteins, force production of the muscle and conduction velocity of the plasma membrane. During the postnatal development of mouse skeletal muscle the density of DHPR increased. By the time of DHPR appearance, the expression of sodium channels had started and the typical assembly of basic structural components and membrane compartments was clearly detectable. According to the histochemical analysis, the DHPR was selectively expressed in type IIA muscle fibres of mouse. In addition to the fibre type specificity, the uneven distribution of DHPRs was also seen at the muscle level. The attenuation of the contraction force after addition of DHPR blocker was largest in muscles with a high percentage of type IIA fibres. In fish muscles, the distribution of DHPR was homogenous and the density between different fibre types was quite similar. In gastrocnemius muscle of mouse, the density and mRNA expression of DHPR increased significantly by 21.5 and 66.8%, respectively, after a 15-week aerobic exercise programme. The increase correlated significantly with the raise in % myosin heavy chain IIa isoform. In thigh and heart muscles, no significant changes were observed. In fish, the environmental change following hatchery release and downstream migration of 46.5 km induced an increase in the DHPR density in swimming muscles. Furthermore, a transition of phenotypic profile from fast-to-slow fibres was observed. Taken together, the present data provide evidence for the fact that the expression of DHPR increases during postnatal development. Moreover, the expression correlates with a specific fibre-type metabolism, thus having an impact on the overall contractile properties of the muscle. This is further manifested as an increase in the DHPR density after endurance training in mammalian as well as in fish muscle. In addition, a strong correlation exists between the level of muscle activity and the density of DHPR. / Tiivistelmä Poikkijuovaisen lihaksen solukalvolla esiintyvä dihydropyridiini (DHP) reseptori toimii jännitesensorina lihaksen ärsytys-supistus kytkennässä. Tässä työssä tutkittiin DHP reseptorin erityispiirteitä sekä erilaisten fysiologisten tekijöiden vaikutusta reseptorin ilmenemiseen. DHP reseptorien visualisointiin kehitettiin histologinen värjäysmenetelmä, jossa merkkiaineena toimi fluorofori-konjugoitu DHP molekyyli. Lisäksi työssä tutkittiin lihaksen proteiinien ekspressiota, lihaksen voimantuottoa sekä solukalvon johtonopeutta erilaisten määritysmenetelmien ja elektrofysiologisten mittausmenetelmien avulla. Tulokset osoittivat, että yksilönkehityksen aikana DHP reseptorien tiheys kasvoi hiiren poikkijuovaisessa lihaksessa. DHP reseptorien ekspression alkaessa natriumkanavat olivat jo ilmaantuneet solukalvolle ja lihassolun rakenne oli pitkälle erilaistunut. Histokemiallisten määritysten perusteella DHP reseptorin ekspressio oli selektiivistä. Reseptoreita esiintyi runsaimmin tyypin IIA soluissa. Reseptoriproteiinin solutyyppispesifisyys oli huomattavissa myös lihastasolla. Tulosten mukaan proteiinin salpaaja alensi lihaksen supistumisvoimaa erityisesti niissä hiiren lihaksissa, joiden solutyyppikoostumuksessa tyypillä IIA on suuri prosentuaalinen osuus. Kalan lihaksissa DHP reseptorit olivat homogeenisesti jakautuneet. Lisäksi reseptoritiheys oli samankaltainen eri solutyyppien välillä. 15 viikon aerobinen harjoittelu lisäsi sekä DHP reseptorin proteiini- että mRNA- ekspressiota tilastollisesti merkitsevästi (21,5 ja 66,8 %) hiiren kantalihaksessa. Ekspression kasvu korreloi merkitsevästi samanaikaisesti tapahtuneen myosiini isomuoto IIa määrän kasvun kanssa. Reisi- ja sydänlihaksessa merkittäviä muutoksia ei havaittu. Kalan uintilihaksissa DHP reseptorien tiheys kasvoi vapauttamisen jälkeisen ympäristön muutoksen ja 46,5 km pituisen vaelluksen jälkeen. Lisäksi lihasten solutyyppikoostumuksessa tapahtui muutos kohti hitaasti supistuvia solutyyppejä. Yhteenvetona voidaan todeta, että saatujen tulosten perusteella DHP reseptorien ekspressio kasvaa syntymän jälkeen hiiren poikkijuovaisessa lihaksessa. Solujen erilaistuessa ekspressio korreloi solutyyppimetabolian kanssa vaikuttaen edelleen lihaksen supistumisominaisuuksiin. Tästä johtuen myös kestävyysharjoittelun seurauksena DHP reseptorien määrä kasvaa sekä nisäkkään että kalan lihaksissa. Erityisesti lihaksen aktiivisuudella on merkitystä DHP reseptorin ekspressioon.