The Impact of Acute and Chronic Weight Restriction and Weight Regulation practices on Physiological, Osteogenic, Metabolic and Cognitive Function in Elite Jockeys

Horse racing is a weight category sport. One of the key challenges facing jockeys is the pressure of “making weight” throughout the protracted racing season. Aim: The aim of this study was to examine the effect of a chronically weight restrictive lifestyle and acute weight loss practices on aspects of physiological, osteogenic, metabolic and cognitive function in jockeys. Methods: The primary aim was achieved through the completion of four related studies. Study One: The effect of a 4% reduction in body mass in 48 hours on physiological and cognitive function was assessed through performance on an incremental cycle ergometer test to volitional exhaustion and a computer based cognitive test battery. Study Two: Bone mass was compared between jockeys (flat and national hunt), elite amateur boxers and a group of age, gender and BMI matched controls. Study Three: Bone mass, bone turnover and endocrine factors related to growth and metabolism were analysed in a group of jockeys and age, gender and BMI matched controls. Study Four: The impact of 6 months whole body vibration therapy (0.3 g and 30 Hz) on bone mass and turnover was analysed in a group of professional jockeys. Results: In study one maximal aerobic exercise performance was negatively affected following a 4% loss in body mass in 48 hours as evidenced by a reduction in peak power output achieved and an increase in submaximal cardiovascular strain. No changes to cognitive performance were identified in this study. In study two both groups of jockeys had lower bone mass at a number of sites than either the boxer or control groups. Adjustment of bone data revealed that differences in height and lean mass accounted for some of the variation between the groups, but that additional factors were present which may have impacted on bone mass in. Study three showed that bone mass was reduced and bone resorption increased in a jockey group. Elevated SHBG and reduced IGF-1 levels in comparison to an age, gender and BMI matched control group appeared to have a role to play in this finding. No aspect of body composition, bone mass or turnover was affected by the vibration therapy protocol used within study four. Conclusion: Results from this research appeared to indicate that aspects of physiological, osteogenic and metabolic function are affected in jockeys. This is likely to have occurred in response to a chronically weight restricted lifestyle. These findings may convey both long and short term health risks to jockeys and as such represent a major health and safety concern to the racing industry

Beyond muscle: the effects of creatine supplementation on brain creatine, cognitive processing, and traumatic brain injury

The ergogenic and therapeutic effects of increasing muscle creatine by supplementation are well-recognized. It appears that similar benefits to brain function and cognitive processing may also be achieved with creatine supplementation, however research in this area is more limited, and important knowledge gaps remain. The purpose of this review is to provide a comprehensive overview of the current state of knowledge about the influence of creatine supplementation on brain function in healthy individuals. It appears that brain creatine is responsive to supplementation, however higher, or more prolonged dosing strategies than those typically used to increase muscle creatine, may be required to elicit an increase in brain creatine. The optimal dosing strategy to induce this response, is currently unknown, and there is an urgent need for studies investigating this. When considering the influence of supplementation strategies on cognitive processes, it appears that creatine is most likely to exert an influence in situations whereby cognitive processes are stressed, e.g. during sleep deprivation, experimental hypoxia, or during the performance of more complex, and thus more cognitively demanding tasks. Evidence exists indicating that increased brain creatine may be effective at reducing the severity of, or enhancing recovery from mild traumatic brain injury, however, only limited data in humans are available to verify this hypothesis, thus representing an exciting area for further research

A comparison of the physiological demands of two commercially available cycle ergometers in trained cyclists

Cycling ergometers are routinely used in a laboratory setting to evaluate physiological function and monitor changes in training status. One limitation of many cycle ergometers, in relation to the performance testing, is their inability to replicate the cyclist own specific cycling position thereby bringing the validity of the ergometer used into question. Purpose: The purpose of this study was to compare the aerobic and anaerobic energy demands of two commercially available cycle ergometers in trained cyclists. The first ergometer allowed full adjustment of cycling position and was electromagnetically braked (EB). The second ergometer allowed for saddle height adjustment only and was resistance braked (RB). Methods: Ten trained male cyclists were tested on 2 separate occasions within a 14 day period under the same conditions. Subjects performed a 30 second Wingate maximal sprint test followed 60 minutes later by a continuous maximal incremental step test on either the EB or RB cycle ergometer, in a random order. The Wingate test was performed at 9% of body mass and for 30 seconds with a 5 second speed up period. The incremental test started at 100W and increased in resistance by 50W every 3 minutes until volitional exhaustion. Heart rate, VO2, power output and blood lactate were measured during the maximal incremental test. Results: The results showed a significant difference (p<0.01) for the Wingate test between the RB and EB both in terms of peak power output (POmax) and mean power output (POmean) with subjects generating greater power outputs on the EB. During the maximal incremental test, significant differences (p<0.01) were found between EB and RB for submaximal power output, heart rate, and VO2 at both lactate threshold 1 (1mmol.l-1 rise above baseline, LT1) and onset of blood lactate accumulation (4mmol.l-1 blood lactate reference point, OBLA), as well as peak power output at VO2max (PVO2max). Conclusions: Overall it was shown that significant differences in physiological demands were present between the two ergometers under both anaerobic and aerobic conditions. This is may in part be explained by the different positions that the cyclists adopted on either ergometer. Further research is required to compare the findings of the current study with actual cycling performance

The relationship between adipose mass and bone density in an over-weight/obese population: a systematic review protocol.

This review aims to look at the relationship between adipose mass and bone density in an overweight/obese population. The available evidence does appear to support evidence of a positive relationship between adipose mass and bone density when considered from a population level. There are however factors associated with an overweight or obese state, that have been shown to be detrimental to bone health, e.g. an increased state of oxidative stress, and physical inactivity. It is possible therefore, that the relationship between adipose and bone mass, which appears positive when considered from a population perspective, may in fact not be when considered from the upper end of the adiposity continuum

Effects of self-monitoring of heart rate and additional sprint running on exercise intensity and technical performance during small-sided games in soccer.

The purpose of this study was to assess whether relatively simple interventions including self monitoring of heart rate and the use of targeted sprints for those with the lowest relative HR values (%HRmax) could be used to increase exercise intensity during small sided games (SSGs) in soccer. A secondary aim of the study was to assess the effect of these interventions on overall gameplay. Fourteen male semi-professional players performed SSGs (6 vs. 6) under four conditions including a control, a self-monitoring approach where players monitored their own HR via a wristwatch, and two sprint conditions where players with HR values below 90%HRmax performed sprints either during the game or during the recovery period between games. A linear mixed effects model was used to test for main effects whilst accounting for covariances between observations made on the same player. The results identified relatively small but significant differences in average %HRmax (p<0.001) and RPE values (p<0.001) between the three modified conditions and the control. No significant differences were found between any of the modified conditions for measures of exercise intensity. On average, the modified conditions resulted in a 3.7% increase in %HRmax values and a 9.3% increase in RPE. The results from this study demonstrate that exercise intensity of SSGs in soccer can be increased by relatively simple and practical manipulations, the most basic of which requires only the use of inexpensive HR monitors

Can selenium supplementation modify oxidative stress in-vitro?

Two thirds of the UK population are either overweight or obese (body mass index (BMI) 25-29.9 and >30 kg/m2 respectively) and are typically characterised by systemic oxidative stress (OS); deemed to play a key role in cardiovascular disease (CVD) development. OS results from chronically high reactive oxidative species (ROS) formation and reduced antioxidant status. OS plays a key role in CVD development by initiating atherosclerosis (fatty plaque accumulation within the arterial walls); therefore obese individuals are at increased risk of atherosclerosis development. Increased monocyte ROS generation instigates atherosclerotic plaque formation by increasing the recruitment, binding and transmigration of monocytes across arterial endothelial cells and into the arterial wall. An increased dietary antioxidant intake or up-regulation of endogenous antioxidant enzymes may counteract this OS state and therefore lower CVD risk. Selenium is an essential dietary micronutrient incorporated within the catalytic site of endogenous antioxidant Glutathione Peroxidase (GPx) enzymes, which protect cells from OS and consequent cell damage. There is, however, a lack of knowledge concerning the effect of selenium supplementation in an OS state representative of sedentary overweight/obese individuals. The aim of this work was to investigate the ability of selenium supplementation to modify monocyte cell viability/ROS production under OS. ITEM WAS A POSTER PRESENTATION AT 1ST ANNUAL MEETING OF THE SCOTTISH SOCIETY OF CYTOMICS (SCC) 2014. TRANSLATIONAL CYTOMETRY FROM BENCH TO BEDSID

Time-course analysis following initial warm-up to inform pre-pitch entry preparations of soccer substitutes.

The purpose of this study was to investigate the time-course of decrements in physical performance following a pre-match warm-up in soccer players. Knowledge of this information could be used to inform re-warm-ups and pre-pitch entry practices of soccer substitutes. Data were collected over five sessions with 12 male youth professionals (15-17 yrs). Across the five sessions each player performed countermovement jumps (CMJ) and drop jumps (30 and 40 cm), pre-warm-up, immediately post-warm-up, and following 10-, 20-, 30-, 40-, and 50-minutes of inactivity. Physical performance was assessed by jump height and calculation of reactive strength index (RSI). Hierarchical generalized linear models (HGLMs) were fitted within a Bayesian framework to identify plausible time to achieve 10 to 50% decrements of the initial pre to post warm-up improvement. Mean improvements of 5.4 cm (95%CrI: 4.8 to 6.0), 0.24 ms-1 (95%CrI: 0.19 to 0.29), and 0.32 ms-1 (0.27 to 0.36) were obtained for the CMJ, and RSI measured from the 30 and 45 cm box, respectively. Decrements for all assessments were non-linear with the steepest rates of decline measured in the initial periods following warm-up. High probabilities were calculated (p ≥ 0.979) that up to 50% of the initial warm-up improvement for the CMJ would be lost between 20 and 30 minutes. The results of this study provide a guide for future research and practitioners managing the pre-pitch entry of soccer substitutes. It is suggested that practitioners consider and assess the effectiveness of exposing players to a re-warm-up between 20- and 30-minutes prior to pitch entry to maintain performance capabilities

Physiological, haematological and performance characteristics of ultra endurance cyclists competing in the inaugural race around Ireland

Ultra-endurance events are a growing area within the sport of cycling. The Race Around Ireland (RAI) is a non-stop event where cyclists must complete the 2,170km route in under 96 hours. Purpose: The purpose of this study was to investigate the physiological, haematological and performance characteristics of members of a 4 man team before, during, and after the RAI. Methods: Four trained male cyclists were tested on 2 separate occasions within a 14 day period, with the second bout of testing performed within 7 days of the start of the race, to determine baseline values. Each cyclist completed a maximal incremental test on an electromagnetically braked cycle ergometer, commencing at 100W and increasing in intensity by 50W every 3 minutes until volitional exhaustion. Heart rate, VO2, power output and blood lactate were measured during the test. Following a standardized recovery period, each cyclist then completed a 20 minute maximal performance test (MPT) designed to mimic the demands of the RAI. Baseline blood samples were taken prior to each testing session to facilitate a detailed haematological analysis. Blood samples were also taken before the start of the race, at set intervals during the race, as well as on the race completion. Subjects were also weighed and urine samples collected at the same time points in order to assess hydration status using urine specific gravity (Usg). Further testing was carried out 7 days (haematology), and 14 days (haematology and MPT) post race. Results: No significant differences were found between the MPT results pre and post race. Significant differences were found for white blood cells (WBC) and granulocyte count (p<0.01), haematocrit, haemoglobin, lymphocytes, and red blood cells (p<0.05). No significant difference was observed for changes in body mass or Usg. Conclusions: Variations in WBC and other immune function markers showed initial decrease followed by a gradual elevation during the race. However this did not seem have an impact on the post race MPT. Although there appears to be a significant change in immune function during ultra endurance cycling, this may not lead to a subsequent performance decrement. However, analysis may be complicated by the specific race tactics adopted by the team during the race and the time course of post race assessment

Protein and bone health across the lifespan

Bone health is determined by the rate of accrual in early life, followed by the rate of age associated bone loss. Dietary protein intake might have a role in bone health across both of these phases via pleiotropic mechanistic pathways. Herein we summarise the pathways through which protein may exert either a positive or negative influence on bone. In Section 1, we describe the acid-ash hypothesis, which states that a high protein intake may lead to an acidic residue that must be neutralised through the leaching of calcium and other minerals from the bone, subsequently leading to demineralisation and bone weakening. Conversely, and as described in Section 2, protein intake may act to strengthen bone by stimulating the activity of various anabolic hormones and growth factors, or by optimising muscle mass and functionality, which itself has an osteogenic influence. The net effect of these contrasting pathways is described in Section 3, where a number of meta-analyses have demonstrated that higher protein intakes have a small positive impact on bone mass and fracture risk. Sometimes higher than recommended protein intakes are advised, e.g., during the earlier and later phases of the lifespan or during reduced energy availability. We conclude that protein is an essential nutrient for bone health, although further research is required to clarify the mechanistic pathways through which it exerts its influence, along with clarification of the quantities, food sources and timing to allow for the optimisation of this protective influence and ultimately a reduction in fracture risk