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Objectives National dietary guidelines were introduced in 1977 and 1983, by the US and UK governments to reduce coronary heart disease (CHD) mortality by reducing dietary fat intake. Our 2016 systematic review examined the epidemiological evidence available to the dietary committees at the time; we found no support for the recommendations to restrict dietary fat. The present investigation extends our work by re-examining the totality of epidemiological evidence currently available relating to dietary fat guidelines. Methods A systematic review and meta-analysis of prospective cohort studies currently available, which examined the relationship between dietary fat, serum cholesterol and the development of CHD, were undertaken. Results Across 7 studies, involving 89 801 participants (94% male), there were 2024 deaths from CHD during the mean follow-up of 11.9±5.6 years. The death rate from CHD was 2.25%. Eight data sets were suitable for inclusion in meta-analysis; all excluded participants with previous heart disease. Risk ratios (RRs) from meta-analysis were not statistically significant for CHD deaths and total or saturated fat consumption. The RR from meta-analysis for total fat intake and CHD deaths was 1.04 (95% CI 0.98 to 1.10). The RR from meta-analysis for saturated fat intake and CHD deaths was 1.08 (95% CI 0.94 to 1.25). Conclusions Epidemiological evidence to date found no significant difference in CHD mortality and total fat or saturated fat intake and thus does not support the present dietary fat guidelines. The evidence per se lacks generalisability for population-wide guidelines.

Objectives National dietary guidelines were introduced in 1977 and 1983, by the USA and UK governments to reduce coronary heart disease (CHD) mortality by reducing dietary fat intake. Our 2015 systematic review examined randomised controlled trial (RCT) evidence available to the dietary committees at the time; we found no support for the recommendations to restrict dietary fat. What epidemiological evidence was available to the dietary guideline committees in 1983? Methods A systematic review of prospective cohort studies, published prior to 1983, which examined the relationship between dietary fat, serum cholesterol and the development of CHD. Results Across 6 studies, involving 31 445 participants, there were 1521 deaths from all-causes and 360 deaths from CHD during the mean follow-up of 7.5±6.2 years. The death rates were 4.8% and 1.1% from all-causes and CHD respectively. One study included men with previous heart disease. The death rate from CHD for those with, and without previous myocardial infarction was 20.9% and 1.0% respectively. None of the six studies found a significant relationship between CHD deaths and total dietary fat intake. One of the six studies found a correlation between CHD deaths and saturated dietary fat intake across countries; none found a relationship between CHD deaths and saturated dietary fat in the same population. Conclusions 1983 dietary recommendations for 220 million US and 56 million UK citizens lacked supporting evidence from RCT or prospective cohort studies. The extant research had been undertaken exclusively on males, so lacked generalisability for population-wide guidelines.

Acclimatisation to environmental hypoxia initiates a series of metabolic and musculocardio-respiratory adaptations that influence oxygen transport and utilisation, or better still, being born and raised at altitude, is necessary to achieve optimal physical performance at altitude, scientific evidence to support the potentiating effects after return to sea level is at present equivocal. Despite this, elite athletes continue to spend considerable time and resources training at altitude, misled by subjective coaching opinion and the inconclusive findings of a large number of uncontrolled studies. Scientific investigation has focused on the optimisation of the theoretically beneficial aspects of altitude acclimatisation, which include increases in blood haemoglobin concentration, elevated buffering capacity, and improvements in the structural and biochemical properties of skeletal muscle. However, not all aspects of altitude acclimatisation are beneficial; cardiac output and blood flow to skeletal muscles decrease, and preliminary evidence has shown that hypoxia in itself is responsible for a depression of immune function and increased tissue damage mediated by oxidative stress. Future research needs to focus on these less beneficial aspects of altitude training, the implications of which pose a threat to both the fitness and the health of the elite competitor. Paul Bert was the first investigator to show that acclimatisation to a chronically reduced inspiratory partial pressure of oxygen (P1O2) invoked a series of central and peripheral adaptations that served to maintain adequate tissue oxygenation in healthy skeletal muscle, physiological adaptations that have been subsequently implicated in the improvement in exercise performance during altitude acclimatisation. However, it was not until half a century later that scientists suggested that the additive stimulus of environmental hypoxia could potentially compound the normal physiological adaptations to endurance training and accelerate performance improvements after return to sea level. This has stimulated an exponential increase in scientific research, and, since 1984, 22 major reviews have summarised the physiological implications of altitude training for both aerobic and anaerobic performance at altitude and after return to sea level. Of these reviews, only eight have specifically focused on physical performance changes after return to sea level, the most comprehensive of which was recently written by Wolski et al. Few reviews have considered the potentially less favourable physiological responses to moderate altitude exposure, which include decreases in absolute training intensity, decreased plasma volume, depression of haemopoiesis and increased haemolysis, increases in sympathetically mediated glycogen depletion at altitude, and increased respiratory muscle work after return to sea level. In addition, there is a risk of developing more serious medical complications at altitude, which include acute mountain sickness, pulmonary oedema, cardiac arrhythmias, and cerebral hypoxia. The possible implications of changes in immune function at altitude have also been largely ignored, despite accumulating evidence of hypoxia mediated immunosuppression. In general, altitude training has been shown to improve performance at altitude, whereas no unequivocal evidence exists to support the claim that performance at sea level is improved. Table 1 summarises the theoretical advantages and disadvantages of altitude training for sea level performance. This review summarises the physiological rationale for altitude training as a means of enhancing endurance performance after return to sea level. Factors that have been shown to affect the acclimatisation process and the subsequent implications for exercise performance at sea level will also be discussed. Studies were located using five major database searches, which included Medline, Embase, Science Citation Index, Sports Discus, and Sport, in

Objective: To investigate the relation between C-reactive protein (CRP), adiposity, physical activity, aerobic fitness and habitual diet in a cohort of schoolchildren. Methods: A cross-sectional study of 164 schoolchildren aged 12–13 years was conducted in two schools. Adiposity was estimated using body mass index and waist circumference. Blood samples were taken after an overnight fast and measured for CRP. Aerobic fitness and habitual physical activity were assessed using the 20 metres multistage fitness test, and a seven-day recall, respectively. A seven-day food diary provided measures of dietary intake. Results: To improve the distribution of this variable, CRP levels were logarithmically transformed in all analyses. There was no significant difference in mean CRP concentration between boys (1.07 (1.33) mg/l) and girls (1.24 (1.87) mg/l) (p⩾0.05). Compared to girls, boys reported significantly higher (i) aerobic fitness 59.2 (20.3) shuttles vs 42.9 (15.3) shuttles, (ii) vigorous activity levels per week 92 (123) minutes vs 11.2 (34.6) minutes and (iii) waist circumference 69.8 (1.1) cm vs 65.2 (0.9) cm (p⩽0.05). Among boys and girls, adiposity was significantly associated with log transformed CRP (p⩽0.05). CRP was not significantly related to any other variable. Conclusion: Elevated CRP was evident in this cohort; however, whether high CRP levels during childhood and adolescence leads to an increased risk of CVD in later life has not been determined. Adiposity was related to CRP concentration, suggesting that reducing adiposity may be effective in lowering CRP and preventing future cardiovascular events.

Background: Respiratory muscle training has been shown to improve both its strength and endurance. The effect of these improvements on whole-body exercise performance remains controversial. Objective: To assess the effect of a 10 week inspiratory resistive loading (IRL) intervention on respiratory muscle performance and whole-body exercise endurance. Methods: Fifteen apparently healthy subjects (10 men, 5 women) were randomly allocated to one of three groups. One group underwent IRL set at 80% of maximum inspiratory pressure with ever decreasing work/rest ratios until task failure, for three days a week for 10 weeks (IRL group). A second placebo group performed the same training procedure but with a minimal resistance (PLA group). IRL and placebo training were performed at rest. The remaining five control subjects performed no IRL during the 10 week study period (CON group). Cycling endurance capacity at 75% V˙o 2 peak was measured before and after the intervention. Results: After the 10 week IRL intervention, respiratory muscle strength (maximum inspiratory pressure) and endurance (sum of sustained maximum inspiratory pressure) had significantly improved (by 34% and 38% respectively). An increase in diaphragm thickness was also observed. These improvements translated into a 36% increase in cycling time to exhaustion at 75% V˙o 2 peak. During cycling trials, heart rate, ventilation, and rating of perceived exertion were attenuated in the IRL group. No changes were observed for the PLA or CON group either in the time to exhaustion or cardiorespiratory response to the same intensity of exercise. Conclusion: Ten weeks of IRL attenuated the heart rate, ventilatory, and perceptual response to constant workload exercise, and improved the cycling time to exhaustion. Familiarisation was not a factor and the placebo effect was minimal.

To examine levels of C reactive protein in users of anabolic androgenic steroids (AAS) compared with age matched control groups consisting of AAS using (but abstinent)/resistance trained and non-drug using/sedentary controls.Subjects included AAS using bodybuilders (n = 10); bodybuilders who denied AAS use (n = 10); sedentary controls (n = 8). Venous blood was sampled, from which serum concentrations of C reactive protein, male sex hormones, and cardiac troponin T were determined.A significantly altered hormonal profile in the AAS using group provided indirect confirmation of AAS use. C reactive protein concentrations were significantly (p0.05) higher in the AAS using bodybuilders. There was no relation between C reactive protein and cardiac troponin T.AAS using bodybuilders had significantly higher C reactive protein concentrations, indicating a greater propensity to develop peripheral arterial disease.

Take home message The duration of exposure to environmental hypoxia during physical exercise is a potential mediator of immune function and athletic performance. Continuous hypoxic training resulted in overt immunodepression whereas intermittent hypoxic training increased physical exercise performance considerably. Although most elite athletes invest a considerable amount of time and resources training at altitude, the practical benefits gained remain to be clearly established despite almost half a century of investigation. Elucidating the potential factors that affect physical performance after return to sea level has been the subject of much interest and controversy. The time spent exposed to the hypoxia of altitude would appear to be an important mediator of sea level performance. A combination of physical exercise and intermittent hypoxia (defined as an exposure time of 30 minutes to 12 hours a day) has been shown to accelerate the normal adaptations invoked by a comparable programme of normoxic training with cardioprotective and performance enhancing benefits.1 In contrast, increased free radical mediated oxidative stress,2 decreased cell mediated immunity,3 and increased incidence of infectious episodes4 have been reported in continuous hypoxia (defined as an exposure time of 24 hours a day). We have previously reported two cases of infectious mononucleosis following chronic exposure to 1500–2000 m.5 Glutamine has been identified as a conditionally essential amino acid required for lymphocyte proliferation and macrophage phagocytosis, and it has been suggested that any physiological decrease in plasma glutamine may impair the host's defence against opportunistic infections.6 In the light of these findings, …

OBJECTIVES: This investigation was designed to monitor altitude acclimatisation in an elite cohort of distance runners and follow the subsequent recovery from infectious mononucleosis which developed in one of these athletes. METHODS: Twenty six national standard distance runners performed treadmill tests 24 days before they travelled to an altitude camp (1500 to 2000 m). One of these athletes was diagnosed as suffering from infectious mononucleosis 14 days after return to sea level. A physician prescribed an individualised training programme which was designed to maximise recovery from the condition, which was monitored on days 16 and 147 after altitude training. RESULTS AND CONCLUSIONS: The data suggest that the athlete was in a state of over-reaching during the altitude sojourn. After return to sea level, the early stages of infectious mononucleosis resulted in a marked impairment in physiological response to endurance exercise, which improved over time. Longitudinal physiological monitoring in conjunction with a carefully prescribed training programme made recovery from this condition possible.

Measurements of free noradrenaline and adrenaline were made in the urine of 28 men sampled after rest and exercise prior to, and following six and twelve weeks of an excercise programme. The training consisted of thirty minutes of running and walking four times per week at an intensity estimated at 75% of the age-predicted maximum heart rate. A fifteen minute standardized cycle ergometer work test was conducted on all subjects prior to the training and following six and twelve weeks of training. Noradrenaline and adrenaline excretions in the urine were measured before and after the work test.

A group of eighty healthy women was studied following two months of programmed exercise (3 x 15 mins/per week) at 60 to 80 percent of age-predicted maximum heart rate. Physical work capacity corresponding to a heartrate of 170 bts. (PWC-170) was determined using a bicycle ergometer. Anthropometric and lung function variables were also ascertained prior to (T1) and following training (T2). The post training measurements of this exercise group, compared with measurements of a sedentary control group, displayed significant changes in PWC-170, resting systolic blood pressure and fat index. There were no significant changes in vital capacity, forced expiratory volume in one second (FEV1), strength and perceived exertion measures (RPE). The implication of these findings are discussed.

The study of physical performance capacity has been of particular interest to the exercise physiologist and many accurate techniques have been designed for the measurement of human performance. The use of maximal oxygen uptake has, since its development by Hill et al in 1924, been regarded as a valuable measure of cardiorespiratory function and used extensively as a criterion of performance capacity of endurance athletes (e.g. Taylor et al, 1955; Saltin and Astrand, 1967; Hanson, 1973).

Thirteen male competitive swimmers (mean age 14.7 years) were studied during maximal exercise on a treadmill, cycle ergometer and biokinetic swim bench. The mean maximal oxygen uptake values elicited (treadmill = 66.5 ml.kg-1 min.-1; cycle ergometer = 61.0 ml.kg.-1 min.-1; biokinetic swimbench = 44.5 ml.kg.-1 min.-1) were higher than those reported elsewhere for children not engaged in intensive training and even when compared with other groups of similarly aged swimmers the values exhibited were some of the highest recorded. The results were directionally similar to those of other studies comparing treadmill and cycle ergometer exercise with the mean maximal oxygen uptake on the cycle ergometer 9% lower than that on the treadmill. There is no other study with which to compare swim bench values but the majority of maximal values were consistently and significantly lower than those achieved on the other ergometers. The swimmers rank within the group was minimally affected by the type of ergometer on which the measurement was made.

The study compared five treadmill protocols (four utilising a motorised, and one a non-motorised, treadmill) on maximum oxygen uptake. The five male and five female subjects, all actively engaged in training, were assigned the tests in random order. Statistical analysis revealed no significant differences between the five protocols for maximal oxygen uptake, maximum ventilation, maximum heart rate and blood lactate inflection point, relative to maximal oxygen uptake. Significant differences were observed between the 3' protocol with incline increments of 1.5% and all other protocols on time to exhaustion (p = less than 0.01) and maximum blood lactate levels (HLA, p = less than 0.05). The results indicate that the protocols used in this study did not significantly influence the maximum oxygen uptake attained.

This study examined the relationship between estimates of alactacid anaerobic power, lactacid anaerobic power and aerobic power in a sample of trained swimmers (age 14.4 yr., n = 8) and a sample of untrained boys (age 13.7 yr., n = 13). The anaerobic power outputs were estimated using a modification of the Wingate Anaerobic Test and aerobic power was estimated using a continuous, incremental cycle ergometer test. In addition to leg power outputs the swimmers' arm power using each energy system was estimated and compared with the corresponding leg value. There was no relationship between the estimates of the power of the three energy systems with either the trained or untrained boys. Furthermore with the trained boys there was no relationship between estimates of the power of the same energy system utilised by different limbs. The data support a specificity hypothesis of energy utilisation during exercise with both trained and untrained adolescent boys.