The lateral batting backlift technique: is it a contributing factor to success for professional cricket players at the highest level?

   Background: This study aimed primarily to investigate the lateral batting backlift technique (LBBT) among semi-professional, professional and current international cricket players. A key question was to investigate whether this technique is a factor that contributes to success for cricket players at the highest levels of the game.  Methods: The participants in this study’s sample (n = 130) were South African semi-professional players (SP) (n = 69), professional players (PP) (n = 49) and South African international professional players (SAI) (n = 12). Biomechanical and video analyses were performed on all the participating groups. Classifiers were utilised to identify the batting backlift technique type (BBTT) employed by all batsmen. All statistics and wagon wheels (scoring areas of the batsmen on a cricket field) were sourced online. A Pearson’s Chi-squared test, Student T-test, one-way analysis of variance and T-test were performed in this study. All analyses were performed using R (R Core Team) at a significance level of α = 0.05.  Results: This study found that a LBBT is more common at the highest levels of batsmanship with batsmen at the various levels of cricket having percentages of the LBBT as follows: SP = 37%; PP = 38%; SAI = 75%; p = 0.001. There was also a noticeably higher difference in the highest scores and career averages between all groups of players, as well as batsmen who either use a straight batting backlift technique (SBBT) or a LBBT. This study also found that SAI batsmen who used the LBBT were more proficient at scoring runs in various areas around the cricket field (according to the wagon wheel analysis).  Conclusion: This study found that a LBBT is a contributing factor for success regarding players wanting to play cricket at the highest levels. Cricket coaches should also pay attention to the direction of the backlift with players, especially when correlating it to various scoring areas on the cricket field. Further in-depth research is required to fully investigate the change in batting backlift techniques among cricket players over a long-term period. 

Carbohydrate intake, obesity, metabolic syndrome and cancer risk? A two-part systematic review and meta-analysis protocol to estimate attributability

INTRODUCTION

Linkages between carbohydrates, obesity and cancer continue to demonstrate conflicting results. Evidence suggests inconclusive direct linkages between carbohydrates and specific cancers. Conversely, obesity has been strongly linked to a wide range of cancers. The purpose of the study is to explore linkages between carbohydrate intake and cancer types using a two-step approach. First the study will evaluate the linkages between carbohydrate intake and obesity, potentially stratified by metabolic syndrome status. Second, the estimated attributable fraction of obesity ascribed to carbohydrate intake will be multiplied against obesity attributable fractions for cancer types to give estimated overall attributable fraction for carbohydrate versus cancer type.

METHODS AND ANALYSIS

We will perform a comprehensive search to identify all possible published and unpublished studies that have assessed risk factors for obesity including dietary carbohydrate intake. Scientific databases, namely PubMed MEDLINE, EMBASE, EBSCOhost and ISI Web of Science will be searched. Following study selection, paper/data acquisition, and data extraction and synthesis, we will appraise the quality of studies and risk of bias, as well as assess heterogeneity. Meta-weighted attributable fractions of obesity due to carbohydrate intake will be estimated after adjusting for other potential confounding factors (eg, physical inactivity, other dietary intake). Furthermore, previously published systematic reviews assessing the cancer-specific risk associated with obesity will also be drawn. These estimates will be linked with the attributability of carbohydrate intake in part 1 to estimate the cancer-specific burden that can be attributed to dietary carbohydrates. This systematic review protocol has been developed according to the 'Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) 2015'.

ETHICS AND DISSEMINATION

The current study will be based on published literature and data, and, as such, ethics approval is not required. The final results of this two part systematic review (plus multiplicative calculations) will be published in a relevant international peer-reviewed journal.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42015023257.

Perceived exertion influences pacing among ultramarathon runners but post-race mood change is associated with performance expectancy

Objectives. This study investigated whether post-race mood changes among ultramarathon runners are associated with perceived exertion or the discrepancy between their actual and predicted performance times.Methods. Eight runners completed the Puffer ultramarathon, which is a challenging 73 km mountainous race across Table Mountain National Park in South Africa. Each runner completed a series of profile of mood state questionnaires (POMS) 2 days before the race (baseline), on the morning of the race (pre-race) and immediately after the race (post-race). Ratings of perceived exertion (RPE) were measured at 13 points during the race using the Borg 6-20 scale. The accuracy of performance expectationswas measured as the difference between runners’ actual and predicted race times.Results. Average completion time was 11:31:36±00:26:32 (h :mm:ss), average running speed was 6.4±2.2 km.hr-1 and averageRPE was 14.1±2.0. Increased POMS confusion was found before the race (33.30.7 v. 37.1±5.2, p=0.014; baseline v. pre-race). Post-race increases in POMS total mood disturbance (TMD) were found (168.3±20 v. 137.5±6.3, p=0.001; post race v. baseline) characterised by decreased vigour (43.3±4.0 v. 33.5±7.0, p=0.008; baseline v. post race), increased confusion (33.3±0.7 v. 38.5±4.8, p=0.006; baseline v. post race) and increased fatigue (37.8±4.8 v. 53.8±7.3, p=0.0003; baseline v. post race). A linear increase in RPE was found during the race (r=0.737, p=0.002).The magnitude of their post-race mood change (r=-0.704, p=0.026) was not found to be associated with runners’ average RPE but was found to be negatively correlated with accuracy of the performance predictions. A time series analysis indicated that POMS TMD would have taken 142±89 min to recover. Conclusions. The results show that RPE influences the wayultramarathon runners pace themselves more than performance expectancy but performance expectations have a greater influence on post-race mood. The magnitude of post-race mood change is associated with the extent of discrepancy between runners’ predicted and actual performance. This has implications for designing appropriate goals and pacing strategies for ultraendurance athletes. 

Previous experience influences pacing during 20 km time trial cycling

OBJECTIVE

To investigate how experience and feedback influence pacing and performance during time trial cycling.

DESIGN

Twenty-nine cyclists performed three 20 km cycling time trials using a Computrainer. The first two time trials (TT1 and TT2) were performed (1) without any performance feedback (n = 10), (2) with accurate performance feedback (n = 10) or (3) with false feedback showing the speed to be 5% greater than the actual speed (n = 9). All participants received full feedback during the third time trial (TT3), and their performance and pacing data were compared against TT2.

RESULTS

Completion time, average power and average speed did not change among the false feedback group, but their pacing strategy did change as indicated by a lower average cadence, 89.2 (SD 5.2) vs 96.4 (6.8) rpm, p<0.05, and higher power during the first 5 km (SMD = 39, 36, 36, 27 and 27 W for 1-5 km respectively). Pacing changed among the blind feedback group indicated by a faster completion time, 35.9 (3.1) vs 36.8 (4.4) min, p<0.05, and power increases during the final 5 km (SMD = 14, 13, 18, 23 and 53 W for 16-20 km respectively). No performance or pacing changes were observed among the accurate feedback group.

CONCLUSIONS

Pacing is influenced by an interaction between feedback and previous experience. Conscious cognitive processes that lead to ratings of perceived exertion and pacing appear to be influenced by previous experience.

Jim Peters' collapse in the 1954 Vancouver Empire Games marathon

On 7 August 1954, the world 42 km marathon record holder, Jim Peters, collapsed repeatedly during the final 385 metres of the British Empire and Commonwealth Games marathon held in Vancouver, Canada. It has been assumed that Peters collapsed from heatstroke because he ran too fast and did not drink during the race, which was held in windless, cloudless conditions with a dry-bulb temperature of 28 degrees C. Hospital records made available to us indicate that Peters might not have suffered from exertional heatstroke, which classically produces a rectal temperature > 42 degrees C, cerebral effects and, usually, a fatal outcome without vigorous active cooling. Although Peters was unconscious on admission to hospital approximately 60 minutes after he was removed from the race, his rectal temperature was 39.4 degrees C and he recovered fully, even though he was managed conservatively and not actively cooled. We propose that Peters' collapse was more likely due to a combination of hyperthermia-induced fatigue which caused him to stop running; exercise-associated postural hypotension as a result of a low peripheral vascular resistance immediately he stopped running; and combined cerebral effects of hyperthermia, hypertonic hypernatraemia associated with dehydration, and perhaps undiagnosed hypoglycaemia. But none of these conditions should cause prolonged unconsciousness, raising the possibility that Peters might have suffered from a transient encephalopathy, the exact nature of which is not understood.

The effect of antecedent fatiguing activity on the relationship between perceived exertion and physiological activity during a constant load exercise task

This study assessed the relationship between the rate of change of the rating of perceived exertion (RPE), physiological activity, and time to volitional exhaustion. After completing a graded exercise test, 10 participants cycled at a constant load equating to 75% of peak oxygen uptake (V O(2)peak) to exhaustion. Participants performed two further constant load exercise tests at 75%V O(2)peak in a fresh state condition within the next 7 days. The RPE was regressed against time and percentage of the time (%time) to volitional exhaustion in both conditions. Despite a lower respiratory exchange ratio (RER) and higher heart rate at the start of the exercise bout in the fatigued condition, there were no differences in RPE at the onset or completion of exercise. As expected, the rate of increase in RPE was greater in the fatigued condition, but there were no differences when expressed against %time. Results suggest that RPE is set at the start of exercise using a scalar internal timing mechanism, which regulates RPE by altering the gain of the relationship with physiological parameters such as heart rate and RER when these are altered by previous fatiguing exercise.

Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon

CONTEXT

Critical assessment of recommendations that athletes consume additional sodium during athletic events.

OBJECTIVE

To evaluate if sodium supplementation is necessary to maintain serum sodium concentrations during prolonged endurance activity and prevent the development of hyponatraemia.

DESIGN

Prospective randomised trial of athletes receiving sodium (620 mg table salt), placebo (596 mg starch), or no supplementation during a triathlon. The sodium and placebo tablets were taken ad libitum, with the suggested range of 1-4 per hour.

SETTING

The 2001 Cape Town Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run).

SUBJECTS

A total of 413 triathletes completing the Ironman race.

MAIN OUTCOME MEASURES

Sodium supplementation was not necessary to maintain serum sodium concentrations in athletes completing an Ironman triathlon nor required to prevent hyponatraemia from occurring in athletes who did not ingest supplemental sodium during the race.

RESULTS

Subjects in the sodium supplementation group ingested an additional 3.6 (2.0) g (156 (88) mmol) sodium during the race (all values are mean (SD)). There were no significant differences between the sodium, placebo, and no supplementation groups with regard to age, finishing time, serum sodium concentration before and after the race, weight before the race, weight change during the race, and rectal temperature, systolic and diastolic blood pressure after the race. The sodium supplementation group consumed 14.7 (8.3) tablets, and the placebo group took 15.8 (10.1) tablets (p = 0.55; NS).

CONCLUSIONS

Ad libitum sodium supplementation was not necessary to preserve serum sodium concentrations in athletes competing for about 12 hours in an Ironman triathlon. The Institute of Medicine's recommended daily adequate intake of sodium (1.5 g/65 mmol) seems sufficient for a healthy person without further need to supplement during athletic activity.

Adherence to cardiovascular risk factor modification in patients with hypertension

AIM

The effectiveness of the support of a healthcare practitioner and a family member in producing changes in cardiovascular risk factor modification was tested in a randomised, controlled trial in patients with hypertension.

METHODS

The primary outcome measured after the 24-week intervention was blood pressure change. Secondary outcomes included patients' adherence to the programme, their knowledge about hypertension, exercise capacity, body weight, self-reported ability to control stress, adherence to medication and salt restriction, as well as symptoms.

RESULTS

There were no marked improvements in blood pressure regulation in either group. The differences between the experimental and control groups were 3 mmHg (CI -6.18-12.18) for systolic blood pressure and 4 mmHg (CI -1.48-9.48) for diastolic blood pressure. The estimated blood pressure effects were small increases in both diastolic and systolic blood pressure, due to larger changes in the control group. These small changes were of no clinical significance. This intervention was not successful in reducing blood pressure of hypertensive patients who participated in a lifestyle programme. Secondary outcomes did show positive changes as a result of the given intervention. The absolute difference in improvement between the two groups was significantly greater for the experimental group than for the control group for the following variables: 24% better adherence to the programme (p = 0.007); 10% higher mean percentage score of hypertension knowledge and its management (p = 0.04); 20% more patients could control their stress levels (p = 0.05); 26% more patients could control their salt ingestion (p = 0.02); and 20% had better adherence to their given medication regimen (p = 0.05). The experimental group had a statistically significant weight reduction of 1 (+/- 4) kg relative to the control group (p = 0.03). Both groups increased their exercise capacity during the trial (p = 0.03). On the completion of the intervention, significantly fewer patients in the experimental group than in the control complained of tiredness (p = 0.05). Patients who had a 75% adherence or more to the programme were found to have maintained their knowledge and their exercise capacity, but not their weight loss after a maintenance phase of 12 weeks, during which time there was no intervention.

CONCLUSION

Patients in a supported environment such as the one in this study were able to modify their cardiovascular risk factors, even though there were non-significant changes in blood pressure reported in this study.

Fluid replacement during marathon running

During endurance exercise, about 75% of the energy produced from metabolism is in the form of heat, which cannot accumulate. The remaining 25% of energy available can be used for movement. As running pace increases, the rate of heat production increases. Also, the larger one's body mass, the greater the heat production at a particular pace. Sweat evaporation provides the primary cooling mechanism for the body, and for this reason athletes are encouraged to drink fluids to ensure continued fluid availability for evaporation and circulatory flow to the tissues. Elite level runners could be in danger of heat illness if they race too quickly in hot/humid conditions and may collapse at the end of their event. Most marathon races are scheduled at cooler times of the year or day, however, so that heat loss to the environment is adequate. Typically, this postrace collapse is due simply to postural hypotension from decreased skeletal muscle massage of the venous return circulation to the heart on stopping. Elite athletes manage adequate hydration by ingesting about 200-800 mL/hour, and such collapse is rare. Athletes "back in the pack" are moving at a much slower pace, however, with heat accumulation unlikely and drinking much easier to manage. They are often urged to drink "as much as tolerable," ostensibly to prevent dehydration from their hours out on the race course. Excessive drinking among these participants can lead to hyponatremia severe enough to cause fatalities. A more reasonable approach is to urge these participants not to drink as much as possible but to drink ad libitum (according to the dictates of thirst) no more than 400-800 mL/hour.

Hyponatremia in distance runners: fluid and sodium balance during exercise

Since its first description in 1985, two opposing theories have evolved to explain the etiology of symptomatic hyponatremia of exercise. The first holds that the condition occurs only in athletes who lose both water and sodium during exercise, and fail to fully replace their sodium losses. The second theory holds that the symptomatic form of this condition occurs in athletes who generate a whole body fluid overload as a result of an excessive fluid intake during prolonged exercise. It is argued that the promotion of the idea that athletes should drink as much as possible during exercise has produced, rather than prevented, the recent increase in the incidence of this condition. A series of case reports and laboratory studies reported in the past 2 years have established that it is a whole body fluid overload, resulting from sustained high rates of fluid intake, that causes the symptomatic hyponatremia of exercise. There is no evidence that, in the absence of fluid overload, the usual sodium deficits generated during exercise can cause this condition. These findings confirm that the potentially fatal condition of symptomatic hyponatremia would be eliminated from sport immediately if all athletes were advised of the dangers of ingesting as much fluid as possible during any exercise that lasts more than 4 hours.

Decreased resting metabolic rate in ballet dancers with menstrual irregularity

We studied 21 ballet dancers aged 19.4 +/- 1.4 years, hypothesizing that undernutrition was a major factor in menstrual irregularity in this population. Menstrual history was determined by questionnaire. Eight dancers had always been regular (R). Thirteen subjects had a history of menstrual irregularity (HI). Of these, 2 were currently regularly menstruating, 3 had short cycles, 6 were oligomenorrheic, and 2 were amenorrheic. Subjects completed a weighed dietary record and an Eating Attitudes Test (EAT). The following physiological parameters were measured: body composition by anthropometry, resting metabolic rate (RMR) by open-circuit indirect calorimetry, and serum thyroid hormone concentrations by radioimmunoassay. R subjects had significantly higher RMR than HI subjects. Also, HI subjects had lower RMR than predicted by fat-free mass, compared to the R subjects. Neither reported energy intake nor serum thyroid hormone concentrations were different between R and HI subjects. EAT scores varied and were not different between groups. We concluded that in ballet dancers, low RMR is more strongly associated with menstrual irregularity than is current reported energy intake or serum thyroid hormone concentrations.

Successful rehabilitation in patients with chronic disease

The aim of medical intervention in patients suffering from chronic diseases is to maintain a life of quality. Patients who have undergone coronary artery bypass surgery provide a good example of an intervention that will not necessarily result in the prolongation of life but the improved quality of life. Rehabilitation outcome should focus on the improved quality of life and the issue of who should be responsible for maintaining improved quality of life. In order to determine if self-responsibility was an aspect of improved quality of life 73 subjects and their spouses were followed up over a period of one year. Self-responsibility was identified as a significant variable (p=0.003) in patients with improved quality of life. Based on the evidence provided by this study it was concluded that unless patients accepted responsibility for their rehabilitation they would not have an improved quality of life.

Development of public policy and physical activity initiatives internationally

Epidemiological, pathological, clinical, and experimental studies over the past 40 years convincingly show that physical inactivity and low physical fitness contribute substantially to the major chronic diseases prevalent in industrialised societies. Several industrialised countries around the world report increases in physical activity participation among adults in recent years, but the prevalence of inactivity remains high. These increases in voluntary exercise are at least partially offset by decreasing daily energy demands due to increased mechanisation at home, at work and during leisure-time. In developing countries, physical inactivity is becoming a prevalent lifestyle due to rapid social and economic changes. Clinical interventions and mass appeals to be more physically active are limited in effectiveness against the background of increasingly sedentary lifestyles. Exercise scientists and public health officials need to turn attention to public policy and legislative initiatives to restructure physical and social environments to encourage more physical activity and discourage sedentary habits.

A fivefold reduction in the incidence of recurrent ankle sprains in soccer players using the Sport-Stirrup orthosis

A study was undertaken to evaluate the effect of a semi-rigid ankle orthosis (Sport-Stirrup) on the incidence of ankle sprains in soccer players during 1 playing season. Senior soccer players were divided into 2 groups: players with previous ankle sprains (N = 258) and players without such history (N = 246). The players in these groups were each randomly allocated to either a semi-rigid orthosis or a control group at the start of the playing season. All subsequent injuries during the season and the total number of playing hours were documented. There was a significant reduction in the incidence of ankle sprains (injuries/1000 playing hours) by ankles in the orthosis group with previous sprains (0.14) compared with the nonbraced group with previous sprains (0.86). The incidence of ankle sprains was significantly higher in the nonbraced group with previous sprains (0.86) compared with the nonbraced group without previous sprains (0.46). Thus, in this study, a semirigid orthosis significantly reduced the incidence of recurrent ankle sprains in soccer players with previous history of ankle sprains.

Exercise training after experimental myocardial infarction increases the ventricular fibrillation threshold before and after the onset of reinfarction in the isolated rat heart

Previous work has shown that exercise training increases the ventricular fibrillation threshold of the isolated perfused rat heart. The aim of our study was to determine whether exercise training that begins after myocardial infarction can similarly increase the ventricular fibrillation threshold. Rats that had suffered an experimental myocardial infarction were subject to a running training program. Thereafter, the ventricular fibrillation threshold was measured before and after the onset of acute reinfarction induced by a second coronary artery ligation. Ventricular fibrillation thresholds were significantly elevated in trained rats during normoxia (13.7 +/- 2.2 vs. 4.7 +/- 0.8 mA, p less than 0.01) and during acute ischemia (6.8 +/- 1.6 vs. 3.0 +/- 0.7 mA, p less than 0.02). The myocardial cyclic AMP level was lower in the nonischemic zone of the trained hearts (0.21 +/- 0.01 vs. 0.28 +/- 0.01 nmol/g, p less than 0.05), which also had lower cyclic AMP levels after epinephrine challenge (0.50 +/- 0.05 vs. 0.73 +/- 0.09 nmol/g, p less than 0.01; 1.41 +/- 0.11 vs. 1.85 +/- 0.09 nmol/g, p less than 0.02 after epinephrine 10(-7) M and 5 x 10(-6) M injection, trained vs. untrained). Both propranolol 10(-6) M and epinephrine 5 x 10(-7) M attenuated the difference in ventricular fibrillation thresholds before and after second coronary artery ligation and eliminated any difference in cyclic AMP content of both the nonischemic and ischemic myocardial tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise in the rehabilitation of CHD patients

The author sets out to show why cardiac patients should follow an exercise regimen and that the important psychological benefits achieved by an exercise rehabilitation programme relate to the healing concept - to making the patient whole again. In addition, the capacity for physical work increases as does the “angina threshold". The safety of the patient is ensured by prescribing exercise based on results of the target heart rate concept. Finally, the author defends walking and jogging as the ideal mode of exercise.

Evidence for an inverse relationship between the ventilatory response to exercise and the maximum whole body oxygen consumption value

Ventilatory responses to submaximal exercise loads indicate that in a population of 895 physically active and sedentary male and female subjects, exercise ventilation is inversely related to predicted VO2max. The correlation coefficients for males and females in this relationship are 0.61 (P less than 0.0001) and 0.26 (P less than 0.0001) respectively. The slopes of regression lines for VE/VO2 and VO2max in female and male subjects are -2.59 and -0.91 respectively. This is associated with changes in composition of the expired air in that PCO2 increases and PO2 decreases with greater VO2max. The difference between the mean oxygen and carbon dioxide partial pressures in expired air of individuals in the highest and lowest VO2max ranges are 1.2 kPa (9 mm Hg) and 0.8 kPa (6 mm Hg) respectively.

Coronary heart disease in marathon runners

Six highly trained marathon runners developed myocardial infarction. One of the two cases of clinically diagnosed myocardial infarction was fatal, and there were four cases of angiographically-proven infarction. Two athletes had significant arterial disease of two major coronary arteries, a third had stenosis of the anterior descending and the fourth of the right coronary artery. All these athletes had warning symptoms. Three of them completed marathon races despite symptoms, one athlete running more than 20 miles after the onset of exertional discomfort to complete the 56 mile Comrades Marathon. In spite of developing chest pain, another athlete who died had continued training for three weeks, including a 40 mile run. Two other athletes also continued to train with chest pain. We conclude that the marathon runners studied were not immune to coronary heart disease, nor to coronary atherosclerosis and that high levels of physical fitness did not guarantee the absence of significant cardiovascular disease. In addition, the relationship of exercise and myocardial infarction was complex because two athletes developed myocardial infarction during marathon running in the absence of complete coronary artery occlusion. We stress that marathon runners, like other sportsmen, should be warned of the serious significance of the development of exertional symptoms. Our conclusions do not reflect on the possible value of exercise in the prevention of coronary heart disease. Rather we refute exaggerated claims that marathon running provides complete immunity from coronary heart disease.