Glucose control, cardiorespiratory fitness, and dietary composition in healthy men.

The overarching aim of my study was to investigate whether continuous glucose monitoring could be utilised in healthy individuals for the earlier identification of individuals that may be at higher risk for the future development of insulin resistance which leads to prediabetes and ultimately type 2 diabetes.

The idea arose from wondering why one healthy person stays healthy while another becomes insulin resistant.  Are there clues in the every-day glucose responses that cannot be picked up by the traditional measures of glucose control that are used to diagnose prediabetes and overt diabetes (fasting glucose, the glucose concentration 2 hours after consumption of 50 g of pure glucose (glucose tolerance), and glycated haemoglobin (HbA1c)).  We thought that maybe some individuals are more tolerable to carbohydrate foods and that continuous glucose monitoring could perhaps be used to identify differences between healthy individuals’ sensitivity to carbohydrate foods.

27 apparently healthy men between the ages of 30 and 50 years volunteered to wear a continuous glucose monitoring sensor for two weeks and to write down everything they eat or drink during this period.   They also underwent a body composition measurement, a treadmill VO2max test and a morning of undergoing all the traditional glucose control tests at their nearest PathCare.

Glycaemic variability measures were calculated from the continuous glucose monitor data.  Whether the study participants had normal or impaired glucose control was determined by the PathCare tests: fasting and 2-h glucose concentrations and HbA1c.  We asked for additional glucose and insulin measures during the glucose challenge test for the purpose of insulin sensitivity calculations.

The diet diaries that the participants kept were analysed and used to determine each individuals’ dietary glycaemic load (GI of the carbohydrate foods x the amount of carbohydrates consumed).  The ratio of energy intake from fats, carbohydrates and protein was also calculated.  Based on this information, the participants were grouped into 3 groups by a K-means cluster analysis.

Glycaemic variability, glucose control, and insulin resistance measures were investigated in relation to cardiovascular fitness, dietary glycaemic load and dietary macronutrient composition.

The strongest association that was found was between insulin sensitivity and cardiovascular fitness.  The strongest association of dietary glycaemic load was with the average height of glucose excursions as measured by the continuous glucose sensors.  The macronutrient groups did not reveal any differences between the traditional glucose control measures, but there were differences in glycaemic variability and insulin sensitivity measures.

As for the overarching aim, we were unable to determine whether at-risk individuals could be identified with the use of continuous glucose monitors. It was, however, clear that insulin resistance develops before any changes in fasting or after-meal blood glucose levels are evident.  The eventual conclusion of the study was that for the early identification of metabolic health declines, focus should be shifted from measuring glucose to measuring insulin.  It was also evident that the most deleterious diet in terms of the development of insulin resistance is one that is high in both carbohydrates and fats.  The dietary group that had the most favourable glucose as well as insulin (and body composition) measures was the low-carbohydrate, high-fat group.

Physiological demands of the Absa Cape Epic mountain bike race and predictors of performance.

The purpose of the study was to determine the exercise intensity of the actual competion (ABSA Cape Epic). Exercise intensity profiling of actual competitions can be useful to understand the physiological demands of these particular cycling events. From a practical point of view, this information will also help to design proper training programs. Furthermore, as many coaches include some races as part of training, the exercise-intensity profile could be useful to understand the training load imposed on athletes. This information can be used to ensure proper training intensities for efficient training adaptation, but also to prevent overtraining.

The main findings of this study were that the men and women in the study sample did not differ from each other in physiological characteristics or in performance outcomes in the laboratory. Therefore all the participants where pooled and divided into a novices and experienced group according to their MTB experience. The two groups didn’t differ in physical or physiological characteristics and performance outcomes in the laboratory. Except for the higher blood lactate response during the TT by the experienced group. The experienced group performed better during the event than the novice group in both the final event time and general classifications category. The experienced group spent statistically significantly more time in the “moderate” HR zone and a greater percentage of time in the “high” HR zones than the novices group. It was also found that there was a decrease in maximal HR obtained in the field from the first day of the event to the last. The same happened for the average stage HR and the percentage time spent in the hard HR zones (80-90% and 90-100% of maximal HR) for both groups. Absolute and relative PO at OBLA showed the strongest correlations to event performance. Low correlations were found between the laboratory variables and average HR during the event, showing that it is not possible to predict the HR response during an event from laboratory variables. Lastly, the correlations found between the laboratory TT variables and event performance was not high and therefore the use of the maximal aerobic test to determine predictors of performance is sufficient.

The study investigated the effect of high intensity interval training (HIIT) on the post-exercise hypotensive response in overweight/obese young women.

Twenty overweight/obese young women were recruited in the study. The participants performed six sessions of HIIT within two weeks and detrained for two weeks. SBP, DBP, and HR were monitored during seated recovery after exercise for 60 min after an acute (first HIIT session) session and the after completion of the six HIIT sessions as well as during detraining from exercise intervention to determine the change from resting values.

The results indicate that both an acute bout and six sessions of HIIT elicited a meaningful PEH response. However, the six sessions of HIIT caused a clinically significant reduction which was approximately twice the acute session. Likewise, detraining showed clinically significant effects in DBP, but SBP returned to near baseline values. This suggests that in only two weeks, the accumulated effects of six sessions of HIIT elicited a greater hypotensive response than after an acute session of HIIT.

The study investigated the effectiveness of rugby specific video-based reactive agility training. The research found that video-based training is a sufficient add-on or alternative method to improve reactive agility in rugby union players. Both video and field-based training significantly improved reactive agility performance when compared to rugby training alone.  It is suggested that this may lead to overall improved performance during competition. When developing reactive agility it is important to include a perceptual and decision-making component.

The effect of graduated compression socks on muscle oxygenation in endurance athletes.
Lara will complete tests on 30 male endurance trained athletes to see how the use of compression socks will affect muscle oxygenation during and post exercise.
Through the research we hope to learn more about the mechanisms whereby compression socks brings about improvement in recovery. We also hope to establish some guidelines for the use of compressions socks in endurance running events.

The results show that definite differences exist between stroke patients and healthy elderly individuals when performing a simple and complex task. The positive effect of low intensity exercise on task performance was clearly seen in both groups, and holds a great deal of practical significance for the development of exercise programmes for healthy individuals, as well as stroke patients. Furthermore, rehabilitation following a stroke has obvious benefits as shown by the positive results of the current study, however, limited research exists to validate these findings, highlighting the need for further research in this area.

The study compared anthropometric, somatotype and functional fitness characteristics of young academy soccer in South Africa and Zimbabwe to distinguish variables that can be relevant for Talent Identification. The study followed a quantitative non-intervention design with a sample of convenience on 74 young soccer players (Age 15.9±0.81) from South African and Zimbabwean soccer academies.

Anthropometric variables were measured following the International Society of the Advancement of Kinanthropometry (ISAK) protocol include: body mass and height; skinfolds – (triceps, subscapular, biceps, iliac crest, supraspinale, abdominal, front thigh, medial calf); Girths – (arm relaxed, arm flexed and tensed, waist, gluteal, and calf); bone breadths – (biepicondylar humerus and biepicondylar femur). Functional fitness variables that were measured include: lower back muscle flexibility (sit and reach test), upper body flexibility (shoulder flexibility), leg power using (vertical and horizontal jumps), overhead throw (2kg medicine ball throw), speed tests (10, 20, and 40m sprint tests), agility (Illinois test) and aerobic fitness (Hoff test). There were no statistically significant differences in age, body mass, height, fat mass, body mass index, lower back flexibility, right shoulder flexibility, 20m sprint, and endurance capacity. Significant differences were found in percentage body fat, sum of 8 skinfolds, fat free mass, somatotype, left shoulder flexibility, upper and lower body power, 10m and 40m sprints. Agility, power and speed were the most distinctive variables that can be used during talent selection, height and weight can be relevant in allocating positional roles to players.

This study investigated the efficacy of graduated compression socks (CS) to modulate the recovery of muscle damage and athletic performance in well-trained distance runners after an actual 56 km ultra-marathon. 
The results suggest that wearing CS during a race leads to reduced muscle damage and muscle soreness which is probably due to less muscle fibre friction and oscillations. Subsequently, these athletes also showed a faster rate of physiological, as well as functional, recovery compared to those who ran without compression socks. It is concluded that compression socks is an effective aid to protect the muscle during strenuous, physical exercise.

This study aimed at determining the influence of running specific prostheses on the performance of an athlete with a unilateral lower limb amputation. We firstly defined some of the mechanical characteristics of the different prostheses models. We then tested the different models of prostheses on an athlete with a unilateral transtibial amputation. This was aimed at determining what influence the different mechanical characteristics as determined in the initial testing has on the physiological and biomechanical performance of the athlete. From these tests we determined that increased stiffness of the prosthesis is more efficient for longer distance sprints such as the 400m. This may be due to a decrease in the contact time with the stiffer prostheses, which decreases the physiological strain on the athlete.

The objective of my PhD dissertation was to determine the exercise training effects on brain oxygenation and cognitive function in older adults. I investigated the effect of three different exercise training interventions (resistance training, high-intensity aerobic interval training and moderate continuous aerobic training) on healthy, older adults’ physical and cognitive functioning over a period of 16 weeks. In short, I found that high-intensity aerobic interval training was more beneficial for gains in physical function; whereas moderate continuous aerobic training was more beneficial for improvement in higher-level cognitive function and cerebral oxygen utilization.