A 26 year physiological description of a National Hockey League team.

The primary purpose of this investigation was to examine the physiological profile of a National Hockey League (NHL) team over a period of 26 years. All measurements were made at a similar time of year (pre-season) in 703 male (mean age +/- SD = 24 +/- 4 y) hockey players. The data were analyzed across years, between positions (defensemen, forwards, and goaltenders), and between what were deemed successful and non-successful years using a combination of points acquired during the season and play-off success. Most anthropometric (height, mass, and BMI) and physiological parameters (absolute and relative VO2 peak, relative peak 5 s power output, abdominal endurance, and combined grip strength) showed a gradual increase over the 26 year period. Defensemen were taller and heavier, had higher absolute VO2 peak, and had greater combined grip strength than forwards and goaltenders. Forwards were younger and had higher values for relative VO2 peak. Goaltenders were shorter, had less body mass, a higher sum of skinfolds, lower VO2 peak, and better flexibility. The overall pre-season fitness profile was not related to team success. In conclusion, this study revealed that the fitness profile for a professional NHL ice-hockey team exhibited increases in player size and anaerobic and aerobic fitness parameters over a 26 year period that differed by position. However, this evolution of physiological profile did not necessarily translate into team success in this particular NHL franchise.

Modification of the Wingate anaerobic power test for rowing: optimization of the resistance setting.

The purpose of the study was to determine the resistance factor that would elicit the highest peak 5 s and mean 30 s power output (PO) during a maximal 30 s anaerobic power test on a rowing ergometer. Thirty-one rowers (17 male and 14 female) were recruited based on the light-weight (LW) (6 male; age 23 +/- 6 yrs and 6 female; age 19 +/- 2 yrs) and heavy-weight (HW) (11 male; age 24 +/- 4 yrs and 8 female; age 27 +/- 8 yrs) rowing categories. Each group completed 5 randomized series of maximal 30 s sprints equivalent to the following forces: 58.9, 63.8, 68.7, 73.7 and 78.6 N for LW males; 83.5, 88.4, 93.4, 98.2 and 103.1 N for HW males; 29.4, 34.3, 39.2, 44.1 and 49.1 N for LW females; and 44.1, 49.1, 54.0, 58.6 and 63.8 N for HW females. The tests were performed on a Gjessing rowing ergometer modified to accommodate greater resistance settings and computer linked to obtain the necessary data. The peak 5 s and mean 30 s PO (W) were determined for each test. A relative load factor (RLF) for determining the amount of resistance to be applied was calculated based on body mass (BM). The RLF settings that elicited the highest peak 5 s PO were 0.109 and 0.102 kg. kg (-1) BM for LW and HW male rowers and 0.111 kg. kg (-1) BM and 0.076 kg. kg (-1) BM for LW and HW female rowers, respectively. The RLF settings for eliciting the highest mean 30 s PO were 0.102 and 0.095 kg. kg (-1) BM for LW and HW male rowers and 0.103 kg. kg (-1) BM and 0.068 kg. kg (-1) BM for LW and HW female rowers, respectively. A 30 second anaerobic test was also performed on a Concept II rowing machine for comparison and it was found to elicit a significantly lower peak 5 s but not 30 s PO in both male and female rowers. Our findings provide RLFs for assessing anaerobic power using a 30 s test in male and female rowers. As well, peak 5 s but not mean 30 s PO is underestimated using the Concept II rowing machine.

A randomized trial of exercise and quality of life in colorectal cancer survivors.

We conducted a randomized controlled trial to determine the effects of a home-based exercise intervention on change in quality of life (QOL) in recently resected colorectal cancer survivors, most of whom were receiving adjuvant therapy. Participants were randomly assigned in a 2:1 ratio to either an exercise (n = 69) or control (n = 33) group. The exercise group was asked to perform moderate intensity exercise 3-5 times per week for 20-30 min each time. The primary outcome was change in QOL as measured by the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) scale. Adherence in the exercise group was good (75.8%) but contamination in the control group was problematic (51.6%). Intention-to-treat analysis revealed no significant differences between groups for change in the FACT-C (mean difference, -1.3; 95% CI, -7.8 to 5.1; P = 0.679). In an 'on-treatment' ancillary analysis, we compared participants who decreased versus increased their cardiovascular fitness over the course of the intervention. This analysis revealed significant differences in favour of the increased fitness group for the FACT-C (mean difference, 6.5; 95% CI, 0.4-12.6; P = 0.038). These data suggest that increased cardiovascular fitness is associated with improvements in QOL in colorectal cancer survivors but better controlled trials are needed.

Effect of concurrent strength and endurance training on skeletal muscle properties and hormone concentrations in humans.

The purpose of this study was to investigate the effect of concurrent strength and endurance training on strength, endurance, endocrine status and muscle fibre properties. A total of 45 male and female subjects were randomly assigned to one of four groups; strength training only (S), endurance training only (E), concurrent strength and endurance training (SE), or a control group (C). Groups S and E trained 3 days a week and the SE group trained 6 days a week for 12 weeks. Tests were made before and after 6 and 12 weeks of training. There was a similar increase in maximal oxygen consumption (VO2max) in both groups E and SE (P < 0.05). Leg press and knee extension one repetition maximum (1 RM) was increased in groups S and SE (P < 0.05) but the gains in knee extension 1 RM were greater for group S compared to all other groups (P < 0.05). Types I and II muscle fibre area increased after 6 and 12 weeks of strength training and after 12 weeks of combined training in type II fibres only (P < 0.05). Groups SE and E had an increase in succinate dehydrogenase activity and group E had a decrease in adenosine triphosphatase after 12 weeks of training (P < 0.05). A significant increase in capillary per fibre ratio was noted after 12 weeks of training in group SE. No changes were observed in testosterone, human growth hormone or sex hormone binding globulin concentrations for any group but there was a greater urinary cortisol concentration in the women of group SE and decrease in the men of group E after 12 weeks of training (P < 0.05). These findings would support the contention that combined strength and endurance training can suppress some of the adaptations to strength training and augment some aspects of capillarization in skeletal muscle.

Blood volume, aerobic power, and endurance performance: potential ergogenic effect of volume loading.

OBJECTIVE: Blood volume (BV) and hemoglobin concentration ([Hb]) play important roles in oxygen transport. Manipulation of both BV and [Hb] can markedly affect systemic oxygen transport and maximal aerobic capacity (VO2max). However, the role of BV in oxygen transport and aerobic performance is not well understood. It has recently been postulated that an acute expansion of BV using plasma volume (PV), independent of changes in [Hb], may represent a potential ergogenic property. Therefore, the primary objective of this review was to determine the potential ergogenic properties of volume loading. DATA SOURCES: An extensive research of Medline and Sport-Discus along with cross-referencing was conducted. Articles were included on the basis of their relevancy to the purpose of this review. Only articles published in English were included in the analysis. STUDY SELECTION: All study designs using human participants were reviewed. DATA EXTRACTION: A systematic analysis of data regarding the effect of BV on the determination of oxygen transport, aerobic capacity, and endurance performance was conducted. Particular emphasis was given to articles that examined BV as the key independent variable. Articles relevant to the evaluation of the impact of BV on aerobic capacity and endurance performance were reviewed according to the strengths of the individual study designs. RESULTS: Seven investigations evaluated the impact of acute changes in BV, independent of changes in [Hb], on VO2max. Of these investigations, three revealed that acute manipulations of BV result in no change or a slight reduction in VO2max. Three investigations revealed a significant improvement in VO2max after acute PV expansion. One investigation revealed a nonsignificant increase in VO2max after acute PV expansion. Seven investigations evaluated the impact of acute changes in BV, independent of changes in [Hb], on endurance performance: two revealed a significant improvement in endurance performance after acute PV expansion, and five revealed an unchanged or reduced endurance performance after acute PV expansion. The majority of investigations showing an improvement in VO2max and/or endurance performance after acute PV expansion were conducted using untrained individuals. CONCLUSION: Volume loading does not result in an improvement in VO2max and/or endurance performance in endurance athletes. Volume loading in untrained individuals may improve VO2max, but does not bring these individuals to the aerobic capacity of endurance-trained athletes. Also, volume loading generally does not lead to improvement in endurance performance, irrespective of its effects on VO2max.

Left ventricular morphology in junior and master resistance trained athletes.

PURPOSE: The objective of this cross-sectional investigation was to assess the effects of short (< 5 yr) versus long-term (> or = 18 yr) resistance training (RT) on left ventricular (LV) dimensions and mass. METHODS: The subjects for this study were 20 elite male powerlifters (8 junior athletes [JA], mean +/- SD, age: 21.1 +/- 1.2 yr and 12 master athletes [MA], age: 46.0 +/- 5.5 yr) and 19 age-matched male controls (8 young controls [YC], age: 21.8 +/- 2.8 yr and 11 middle-aged controls [MAC], age: 46.8 +/- 4.4 yr). Two-dimensionally guided transthoracic M-mode echocardiograms were performed at rest to quantify LV systolic and diastolic cavity dimension (LVIDs and LVIDd, respectively), ventricular septal wall thickness (VST), posterior wall thickness (PWT), LV mass (LVM), and LV systolic function as measured as fractional shortening (FS). RESULTS: Short- or long-term RT was not associated with a significant alteration in LVIDd (JA: 53.2 +/- 4.5 mm, YC: 52.1 +/- 3.7 mm, MA: 53.0 +/- 5.1 mm, MAC: 51.8 +/- 4.4 mm), LVIDs (JA: 33.5 +/- 4.8 mm, YC: 32.9 +/- 3.4 mm, MA: 33.0 +/- 4.4 mm, MAC: 31.4 +/- 3.7 mm), VST (JA: 9.4 +/- 0.9 mm, YC: 9.4 +/- 0.9 mm, MA: 9.4 +/- 1.6 mm, MAC: 9.7 +/- 0.9 mm), PWT (JA: 9.2 +/- 0.9 mm, YC: 9.4 +/- 0.9 mm, MA: 9.0 +/- 1.1 mm, MAC: 9.5 +/- 1.0 mm), LVM (JA: 184.6 +/- 36.1 g, YC: 179.0 +/- 26.5 g, MA, 183.3 +/- 58.1 g, MAC: 184.1 +/- 38.1 g), or FS (JA: 0.37 +/- 0.1%, YC: 0.37 +/- 0.05%, MA: 0.38 +/- 0.1%, MAC: 0.40 +/- 0.04%). CONCLUSIONS: These findings suggest that short or long-term RT as performed by elite junior and master powerlifters does not alter LV morphology or systolic function.

Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise. Part II: Novel techniques and new advances.

For exercise physiologists and sport cardiologists, one of the greatest challenges is to develop a valid, reliable, noninvasive and affordable measure of cardiac output (Q). There are several techniques available to measure Q during exercise conditions. These procedures generally provide accurate and reliable determinations of Q during submaximal exercise, but may be limited during maximal exercise conditions. The most commonly used noninvasive measures are the acetylene (C2H2) and carbon dioxide (CO2) rebreathe methods as reviewed in part I of this article. Only the foreign gas rebreathe method, using C2H2, meets all of the criteria of being noninvasive, easy to use, reliable and valid for use during maximal exercise. New methodologies have recently been developed to measure Q during exercise conditions. Although not as popular as the C2H2 and CO2 rebreathe methods, these methods have increasingly gained favour in exercise physiology and sport cardiology settings. The majority of these measures (if performed meticulously), with the exception of impedance cardiography, provide reasonably accurate and reliable determinations of Q. However, the cost of usage and technological limitations during maximal exercise have prevented these techniques from replacing the conventional measures of Q during exercise conditions. Doppler echocardiography and the modified C2H2 methods hold promise for the assessment of Q during maximal exercise. With further advances in these technologies their use in exercise physiology and sport cardiology setting may become more common.

Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise. Part I: Conventional techniques.

The assessment of cardiac function, particularly cardiac output (Q) during heavy exercise is essential for the evaluation of cardiovascular factors that might limit oxygen transport. A series of invasive and noninvasive techniques has been developed for the assessment and monitoring of Q during resting and submaximal exercise conditions. However, very few techniques have been found to give accurate and reliable determinations of Q during vigorous to maximum exercise. For exercise physiologists and sport cardiologists, maximal exercise data are of primary importance. The 'gold standard' measures of cardiac function are considered to be the direct Fick and dye-dilution methods. These have been widely shown to give accurate and reliable determinations of Q during resting and submaximal exercise conditions; however, their use during maximal exercise conditions is debatable due to the inherent risks involved with each and their increasing inaccuracy during the later stages of vigorous exercise. Thermodilution has also been considered to be a relatively good method for the determination of Q during rest and exercise conditions, but recent authors have questioned its use due to the nature of the measure and its inaccuracy during strenuous exercise. Various noninvasive measures of cardiac function have been developed to overcome the problems associated with the 'gold standard' measures. The first part of this article discusses conventional techniques used in exercise physiology settings. The majority of these provide accurate and reliable determinations of Q during rest and submaximal exercise. However, very few techniques are suitable for maximal exercise conditions. Perhaps only the foreign gas rebreathe using acetylene (C2H2) meets all the criteria of being noninvasive, simple to use, reliable over repeated measurements, accurate and useful during maximal exercise.

Development of a hockey-specific, skate-treadmill VO2 max protocol.

The purpose of this study was to investigate a protocol for the determination of VO2 max utilizing a motor-driven skate treadmill (ST). On separate days, 6 male hockey players completed a ST and a cycle ergometer (BK) VO2 max protocol. The results showed no significant difference between the ST and BK protocols for relative (60.4 +/- 5.09 vs. 59.0 +/- 8.31 ml.kg-1.min-1) and absolute VO2 max values (4.51 +/- 0.50 vs. 4.39 +/- 0.59 L.min-1), respectively. Significantly higher HR max was recorded during the ST protocol (202.3 +/- 4.27 vs. 200.7 +/- 4.55 b.min-1) (p < 0.05). Peak VE and VT were nonsignificant between the two conditions. However, peak f was higher for the ST protocol (63.0 +/- 7.56 vs. 60.2 +/- 7.76 breath.min-1) (p < 0.05). Although the physiological response to both protocols was similar, the ST protocol replicates a hockey stride, which may provide more applicable information for the development of training programs.

Relationship between aerobic fitness and metabolic recovery from intermittent exercise in endurance athletes .

This investigation examined the relationship between several different aerobic fitness test results and measurements of metabolic recovery from intermittent, high-intensity exercise in 16 male cyclists. No significant correlations were found between maximal oxygen consumption, ventilation threshold, various submaximal endurance measures and the rate of metabolic recovery, net excess postexercise oxygen consumption, or blood lactate removal after intermittent high-intensity exercise except for submaximal heart rate (r = .66, p < .05). These data indicate that aerobic fitness assessments do not indicate the ability to recover after intermittent, high-intensity exercise in endurance-trained cyclists.

The influence of maximal aerobic power on recovery of skeletal muscle following anaerobic exercise.

Phosphorus magnetic resonance spectroscopy (31P-MRS) was used to investigate the influence of maximal aerobic power (VO2max) on the recovery of human calf muscle from high-intensity exercise. The (VO2max) of 21 males was measured during treadmill exercise and subjects were assigned to either a low-aerobic-power (LAP) group (n = 10) or a high-aerobic-power (HAP) group (n = 11). Mean (SE) VO2max of the groups were 46.6 (1.1) and 64.4 (1.4) ml.kg-1.min-1, respectively. A calf ergometry work capacity test was used to assign the same relative exercise intensity to each subject for the MRS protocol. At least 48 h later, subjects performed the rest (4 min), exercise (2 min) and recovery (10 min) protocol in a 1.5 T MRS scanner. The relative concentration of phosphocreatine (PCr) was measured throughout the protocol and intracellular pH (pHi) was determined from the chemical shift between inorganic phosphate (Pi) and PCr. End-exercise PCr levels were 27 (3.4) and 25 (3.5)% of resting levels for LAP and HAP respectively. Mean resting pHi was 7.07 for both groups, and following exercise it fell to 6.45 (0.04) for HAP and 6.38 (0.04) for LAP. Analysis of data using non-linear regression models showed no differences in the rate of either PCr or pHi recovery. The results suggest that VO2max is a poor predictor of metabolic recovery rate from high-intensity exercise. Differences in recovery rate observed between individuals with similar VO2max imply that other factors influence recovery.

Dietary fat modifies exercise-dependent glucose transport in skeletal muscle.

Exercise stimulates muscle glucose uptake both directly and by increasing the sensitivity of this process to insulin. This study was designed to investigate whether the level of dietary fat would interact with the action of acute exercise in the presence or absence of insulin. Weanling female Sprague-Dawley rats were fed two levels of dietary fat (5 vs. 20%; wt/wt) for 6 wk. Rats then remained sedentary or were exercised by a single bout of swimming for a total of 2 h with 5-min rest intervals each 0.5 h. Basal (insulin-independent) and insulin-stimulated glucose uptake rates were determined in isolated epitrochlearis muscles by using 3-O-[methyl-3H]methyl-D-glucose. Muscles of sedentary rats fed a high-fat diet showed decreased glucose uptake overall because of a marked decrease in insulin-stimulated uptake. Muscles of rats fed a high-fat diet also showed considerable impairment of insulin-dependent glucose uptake measured both immediately and 3.5 h after exercise. Glucose uptake was suppressed by 64% at half-maximal concentrations of insulin (0.8 nM) and by 34% at maximally stimulating (20 nM) insulin levels. This lowered sensitivity and response to insulin were not altered by acute exercise. Glucose uptake in response to acute exercise (insulin independent) was quantitatively similar in rats fed high- and low-fat diets; rats on high-fat diet, however, showed higher insulin-independent glucose uptake at 3.5 h after exercise.

Epidemiology of recreational and old-timer ice hockey injuries.

OBJECTIVE: To examine the nature and incidence of injuries suffered by a sample of recreational and old-timer ice hockey players. DESIGN: Random sample of teams followed prospectively. SETTING: Various hockey rinks in the Greater Edmonton Region. PARTICIPANTS: Four hundred and thirty-one subjects--287 adult male recreational (AMRL) and 144 male old-timer (OTL) from five leagues were followed over the 1992-93 hockey season. MAIN OUTCOME MEASURES: Injuries sustained during the duration of a hockey season. RESULTS: A total of 151 injuries (100 AMRL and 51 OTL) were reported. The aggregate injury rate was 12.2/1000 player-exposures (12.3 AMRL and 12.0 OTL). The anatomic region most often injured by AMRL players was the head/neck/facial area (32%) while OTL players reported a greater proportion of lower extremity injuries (40%). Both groups reported sprains/strains as the most common diagnosis (35% AMRL and 47% OTL). The predominant injury mechanism for AMRL players was stick contact (24%) and for OTL players was puck contact (23%). No significant differences were detected between the anatomic, diagnostic, and mechanistic distributions of injury between AMRL and OTL players. Seventy-five percent of injuries occurred during league games, 10% during playoff games, 5% during tournament games, and 10% during practices. Penalties were assessed in 31% of injury instances. Forty-two percent of head/neck/facial injuries, 32% of upper extremity injuries, 13% of torso injuries, and 15% of lower extremity occurred as a result of penalizable behavior (p = 0.01). Three percent of players wearing full or half face protectors suffered facial injuries while 9% of players not wearing facial protection reported facial injuries (p = 0.03; Relative Risk = 2.56). CONCLUSIONS: The injury rates observed were lower than reported rates for major/elite hockey. The proportion of players injured through body contact was lower than that observed in adult major/elite hockey while the diagnostic and anatomic distribution of injury was similar. Studies such as this are useful in the development of injury prevention strategies.

Parallel insulin-like growth factor I and insulin resistance in muscles of rats fed a high fat diet.

The possibility of a similarity between insulin-like growth factor-I (IGF-I) and insulin resistance in epitrochlearis muscles of rats fed a high fat diet [20% (wt/wt) fat] vs. a low fat diet [5% (wt/wt) fat] was investigated. Half-maximally and maximally effective concentrations of IGF-I- and insulin-stimulated 3-O-methyl-glucose transport were 2.32 and 25 nM, respectively, for IGF-I, compared with 0.79 and 20 nM for insulin. The high fat diet reduced both responsiveness and sensitivity of IGF-I-stimulated 3-O-methyl-glucose transport in parallel with the impaired insulin-stimulated 3-O-methyl-glucose transport. IGF-I binding at 2.5 nM to incubated epitrochlearis muscle was also decreased by the high fat diet (P < 0.05). Thus, the high fat diet caused simultaneous IGF-I and insulin resistance in rat skeletal muscle. The IGF-I resistance induced by feeding the high fat diet seems at least partially due to a reduction in IGF-I binding.

Knee muscle strength in elite male gymnasts.

This study was launched to establish the profile of knee dynamic concentric strength in elite male gymnasts after it was found that three of the 10-member Canadian men's gymnastics team had incurred anterior cruciate ligament (ACL) rupture. The dynamic concentric force characteristics of the quadriceps and hamstring muscles of 84 male gymnasts were studied at the Canadian National Championships using a Kin-Com isokinetic dynamometer. These tests were performed at 90 degrees/sec and 230 degrees/sec and revealed that the hamstrings to quadriceps peak torque ratio was not only unusually low (0.5) when compared with data collected in previous research, but that this ratio was consistent across all ages, from 12 to 27 years. The torque ratios were also reported at 30 degrees, 45 degrees, and 60 degrees and it was found that the ratios decreased as the joint angle increased and again was consistent across the four age groups. It was also found that the hamstrings to quadriceps peak torque ratio did not increase (hamstrings becoming stronger relative to quadriceps) as velocity of movement increased as has been reported in other studies. It was hypothesized that the large shear forces that are generated about the knee in gymnastics (extrinsically from backward landing and intrinsically from the quadriceps eccentrically contracting), combined with the relatively weak hamstrings, could be one cause for the increasing incidence of ACL injuries in that sport. The results of this study indicate that it would be prudent for clinicians involved with gymnasts to test for knee strength imbalance and to prescribe exercises to correct it when necessary.

Validity of breathing frequency to monitor exercise intensity in trained cyclists.

This study compared breathing frequency (fB) during a ventilation threshold (VT) test with fB during a simulated 40 km time trial (40TT) to assess whether fB can be used to monitor exercise intensity. Twenty-six male cyclists (mean +/- SD VO2max = 4.42 +/- 0274 l.min-1) performed an incremental VT ergometer test and a simulated 40TT on a set of wind-loaded rollers. During the 40TT, expired gas was collected for 3 min using open circuit spirometry at 10 km intervals. A significant correlation (r = 0.89; p < or = 0.05) was found between the fB threshold (VTf) and the gas exchange VT (VTg) (3.42 +/- 0.08 and 3.31 +/- 0.09 l.min-1, respectively). No differences were found in VO2 at the VTf vs. X VO2 (3.48 +/- 0.08 l.min-1) during the simulated 40TT. However, when fB in br.min-1 calculated from the VT test (32.5 br.min-1), was compared with fB during the 40TT (45.6 br.min-1), there was a significant difference. Ventilation, heart rate and the respiratory exchange ratio were all significantly higher during the 40TT. Although a significant relationship was found between the VT test and the 40TT for VTf measured in l.min-1 of VO2 (r = 0.66; p < or = 0.05), fB in br.min-1 obtained from the incremental test should not be used to identify exercise training intensity. These data suggest that during competition, trained athletes exercise at a higher fB than that determined when being tested, implying that fB in br.min-1 may not be a valid measurement of exercise intensity.

L-carnitine increases glucose metabolism and mechanical function following ischaemia in diabetic rat heart.

OBJECTIVE: Stimulation of glucose oxidation by L-carnitine improves mechanical recovery of ischaemic hearts from non-diabetic rats perfused with high levels of fatty acids. The aim of this study was to determine whether L-carnitine also increases glucose oxidation and function in diabetic rat hearts, which have suppressed glucose metabolism. METHODS: Isolated working hearts from six week streptozotocin diabetic and control rats were perfused with 11 mM (5-3H/U-14C)-glucose, 1.2 mM palmitate. Hearts were paced at 260 beats.min-1 during 60 min of low flow ischaemia, and were then subjected to 30 min of aerobic reperfusion. Total myocardial carnitine content in these hearts was first increased by a 60 min aerobic perfusion with 10 mM L-carnitine. RESULTS: Steady state glucose oxidation rates (measured as 14CO2 production) were depressed in diabetic rat hearts compared to control hearts during the initial aerobic period. However, L-carnitine treatment dramatically increased glucose oxidation rates in the diabetic rat hearts, as well as in control hearts. Glycolysis was also lower in diabetic rat hearts compared to control hearts, although L-carnitine treatment significantly increased glycolysis only in the diabetic animals. During reperfusion, steady state rates of glucose oxidation and glycolysis returned to preischaemic values in both the control and diabetic groups. L-carnitine treatment stimulated glucose oxidation during reperfusion in control and diabetic rat hearts. Mechanical function of control hearts returned to 38(SEM 9)% of preischaemic values, whereas in L-carnitine treated hearts function returned to 90(7)% of preischaemic values. Recovery of function was 80(15)% of preischaemic in the diabetic rat hearts, and was increased to 100% of preischaemic function with L-carnitine. CONCLUSIONS: Carnitine improves recovery of function of ischaemic non-diabetic rats by stimulating glucose oxidation during reperfusion, whereas it may be beneficial in diabetic rat hearts by stimulating both glycolysis during ischaemia and glucose oxidation during reperfusion.

Dietary omega-3 and polyunsaturated fatty acids modify fatty acyl composition and insulin binding in skeletal-muscle sarcolemma.

Feeding animals with diets high in saturated fat induces insulin resistance, and replacing saturated fat isocalorically with poly-unsaturated fat, especially long-chain omega-3 fatty acids, will prevent the development of insulin resistance in skeletal-muscle tissue. To investigate the mechanism, rats were fed on high-fat (20%, w/w) semipurified diets for 6 weeks. Diets containing ratios of polyunsaturated/saturated (P/S) fatty acid of 0.25 (low-P/S diet) and 1.0 (high-P/S diet) were used to study the effect of the level of saturated fat. To study the effects of omega-3 fatty acids, diets with a low-P/S ratio containing either 0 (low-omega-3 diet) or 3.3% (high-omega-3 diet) long-chain omega-3 fatty acids from fish oil were fed. Plasma membrane from skeletal muscle was purified. The content of fatty acids in sarcolemmal phospholipid was significantly related to the dietary composition. Insulin binding to intact sarcolemmal vesicles prepared from rats fed on diets high in omega-3 fatty acids increased 14-fold compared with animals fed on the low-omega-3 diet (P < 0.0001). Feeding rats on a diet with a high P/S ratio increased sarcolemmal insulin binding by 2.3-fold (P < 0.05). Increased insulin binding was due to increased receptor number at the low-affinity high-capacity binding site. Dietary effects on insulin binding were eliminated when studies were carried out on detergent-solubilized membranes, indicating the importance of the phospholipid fatty acyl composition for insulin binding. The results suggest that dietary omega-3 and polyunsaturated fatty acids increase insulin binding to sarcolemma by changing the fatty acyl composition of phospholipid surrounding the insulin receptor, and this might be the mechanism by which dietary fatty acids modify insulin action.