Brain oxygenation declines in elite Kenyan runners during a maximal interval training session.

PURPOSE: The purpose of this study was to characterise the cerebral oxygenation (Cox) response during a high-intensity interval training session in Kenyan runners, and to examine any relationship with running performance. METHODS: 15 Kenyan runners completed a 5-km time trial (TT) and a Fatigue Training Test on a treadmill (repeated running bouts of 1-km at a pace 5% faster than their mean 5-km TT pace with a 30-s recovery until exhaustion). Changes in Cox were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxy-haemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI). RESULTS: The number of 1-km repetitions achieved by the participants was 5.5 ± 1.2 repetitions at a mean pace of 20.5 ± 0.7 km h-1. Δ[O2Hb] measured at the end of each running repetition declined progressively over the course of the trial (p = 0.01, ES = 4.59). Δ[HHb] increased during each running bout until the end of the Fatigue Training Test (p < 0.001; ES = 6.0). TOI decreased significantly from the beginning of the test (p = 0.013, ES = 1.83), whereas nTHI remained stable (ES = 0.08). The Cox decline in the Fatigue Training Test was negatively correlated with the speed at which the test was completed (p = 0.017; r = -0.61), suggesting that the best performers were able to defend their Cox better than those of lower running ability. CONCLUSIONS: In conclusion, this study suggests that elite Kenyan runners cannot defend cerebral oxygenation when forced to exercise to their physiological limits. This emphasises the critical importance of pacing in their racing success.

Are gait characteristics and ground reaction forces related to energy cost of running in elite Kenyan runners?

The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h-1 and 20 km ·h-1). VO2 and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg-1· km-1 at 12 km· h-1 and 184.8 ± 9.9 ml· kg-1· km-1 at 20 km· h-1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg-1·km-1 and 0.93 ± 0.07 kcal· kg-1· km-1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h-1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners.

Relationship between vertical jump and maximal power output of legs and arms: effects of ethnicity and sport.

The hypothesis that ethnicity and sport practice influence the relationship between maximal power in cycling (P(max)) and countermovement jump (CMJ) has been studied by relating CMJ and P(max) in two groups (volleyball players, VB, and physical education students, PES) including subjects with Caucasian (67 C) or West African (39 WA) origins. Maximal power of the arms (P(max) Arms) was also measured. A two-way analysis of variance (groups × ethnicity) showed significant effects of both factors upon CMJ, which was higher in WA and VB, P = 0.002 and P < 0.001, respectively. Within WA, CMJ was significantly higher in VB (0.732 ± 0.057 m) than in PES (0.661 ± 0.082 m), although there was no difference in P(max) (14.7 ± 1.7 vs 14.7 ± 1.9 W/kg). CMJ was significantly higher in WA (0.69 ± 0.08 vs 0.65 ± 0.09 m in C, P = 0.002) without significant interethnic difference in P(max) (14.7 ± 1.8 in WA, and 14.8 ± 1.9 W/kg in C). The CMJ-P(max) relationships were different in C and WA (P = 0.003). Therefore, CMJ predicted from P(max) would be underestimated in WA. The same difference was observed for the relationship between CMJ and P(max) Arms. These results were confirmed by the comparison with previous P(max) -CMJ relationship in the literature, collected in Caucasian and African subjects with the same protocols.

Low carbohydrate high fat ketogenic diets on the exercise crossover point and glucose homeostasis.

In exercise science, the crossover effect denotes that fat oxidation is the primary fuel at rest and during low-intensity exercise with a shift towards an increased reliance on carbohydrate oxidation at moderate to high exercise intensities. This model makes four predictions: First, >50% of energy comes from carbohydrate oxidation at ≥60% of maximum oxygen consumption (VO2max), termed the crossover point. Second, each individual has a maximum fat oxidation capacity (FATMAX) at an exercise intensity lower than the crossover point. FATMAX values are typically 0.3-0.6 g/min. Third, fat oxidation is minimized during exercise ≥85%VO2max, making carbohydrates the predominant energetic substrate during high-intensity exercise, especially at >85%VO2max. Fourth, high-carbohydrate low-fat (HCLF) diets will produce superior exercise performances via maximizing pre-exercise storage of this predominant exercise substrate. In a series of recent publications evaluating the metabolic and performance effects of low-carbohydrate high-fat (LCHF/ketogenic) diet adaptations during exercise of different intensities, we provide findings that challenge this model and these four predictions. First, we show that adaptation to the LCHF diet shifts the crossover point to a higher %VO2max (>80%VO2max) than previously reported. Second, substantially higher FATMAX values (>1.5 g/min) can be measured in athletes adapted to the LCHF diet. Third, endurance athletes exercising at >85%VO2max, whilst performing 6 × 800 m running intervals, measured the highest rates of fat oxidation yet reported in humans. Peak fat oxidation rates measured at 86.4 ± 6.2%VO2max were 1.58 ± 0.33 g/min with 30% of subjects achieving >1.85 g/min. These studies challenge the prevailing doctrine that carbohydrates are the predominant oxidized fuel during high-intensity exercise. We recently found that 30% of middle-aged competitive athletes presented with pre-diabetic glycemic values while on an HCLF diet, which was reversed on LCHF. We speculate that these rapid changes between diet, insulin, glucose homeostasis, and fat oxidation might be linked by diet-induced changes in mitochondrial function and insulin action. Together, we demonstrate evidence that challenges the current crossover concept and demonstrate evidence that a LCHF diet may also reverse features of pre-diabetes and future metabolic disease risk, demonstrating the impact of dietary choice has extended beyond physical performance even in athletic populations.

AVPR2 gene and weight changes during triathlons.

The arginine vasopressin receptor 2 (AVPR2) plays an important antidiuretic role in regulating water balance to maintain osmotic equilibrium. The aim of this study was to determine if there were any associations between single nucleotide polymorphisms (SNPs), within the AVPR2 gene, and changes in serum sodium concentrations and/or body weight (BW) in Ironman triathletes. Caucasian male triathletes who completed either the 2000, 2001 or 2006 South African Ironman Triathlons were genotyped (n=570) for at least one SNP. Pre- and post-race serum [Na+] (pre n=514; post n=423) and BWs (pre n=556; post n=552) were measured. Triathletes were divided into 3 groups according to their relative BW loss during the triathlon (BW loss of 0-3, 3-5 and >5%). There was a significant linear trend (p=0.010, x2=6.7) for the distribution of minor haplotypes GCT, GTC and GCC across the 3 BW loss groups. The >5% group had the highest percentage (4.7%) of triathletes with minor haplotypes followed by the 3-5% (3.6%) and 3-0% (0%) groups. In conclusion, the minor haplotype constructs of AVPR2 SNPs were associated with larger BW losses during the Ironman Triathlons. This finding supports a possible genetic contribution to BW loss during endurance exercise events acting through the argine vasopression system.

What limits [V(·)]O(2max)? A symposium held at the BASES Conference, 6 September 2010.

Three modern views about the factors limiting oxygen uptake in healthy humans are set against the original (early 1920s) concept of A. V. Hill and colleagues. The majority view for most of the intervening time has been that cardiac output is the essential limiting function. Among recent research in support of this contention is that, in quadrupeds, pericardiectomy, which allows greater diastolic filling, elevates maximum oxygen uptake; however, the relevance to bipedal exercise can be questioned. In any case, algebraic analyses of model systems indicate that all identifiable stages on the oxygen transport pathway, from pulmonary diffusion to oxidative phosphorylation in skeletal muscle mitochondria, materially influence maximum uptake. Thus, if a high cardiac output is to be of benefit, all the other steps must function better too. Nevertheless, these two viewpoints concur that the limit to maximum oxygen uptake is somatic. In contrast, there are strong indications that at altitudes where oxygen availability is about half that at sea level, cerebral oxygenation is a limiting factor, and some recent experiments raise the possibility that it might be a substantial influence at sea level also. Clearly, consensus cannot yet be reached on the question posed in the title.

The role of emotions on pacing strategies and performance in middle and long duration sport events.

Thepacing strategy may be defined as the process in which the total energy expenditure during exercise is regulated on a moment-to-moment basis in order to ensure that the exercise bout can be completed in a minimum time and without a catastrophic biological failure. Experienced athletes develop a stable template of the power outputs they are able to sustain for different durations of exercise, but it is not known how they originally develop this template or how that template changes with training and experience. While it is understood that the athlete's physiological state makes an important contribution to this process, there has been much less interest in the contribution that the athlete's emotional status makes. The aim of this review is to evaluate the literature of physiological, neurophysiological and perceptual responses during exercise in order to propose a complex model interpretation of this process which may be a critical factor determining success in middle- and long-duration sporting competitions. We describe unconscious/physiological and conscious/emotional mechanisms of control, the focus of which are to ensure that exercise terminates before catastrophic failure occurs in any bodily system. We suggest that training sessions teach the athlete to select optimal pacing strategies by associating a level of emotion with the ability to maintain that pace for exercise of different durations. That pacing strategy is then adopted in future events. Finally, we propose novel perspectives to maximise performance and to avoid overtraining by paying attention also to the emotional state in training process.

A novel submaximal cycle test to monitor fatigue and predict cycling performance.

OBJECTIVE: The purpose of this study was to determine the reliability and predictive value of performance parameters, measured by a new novel submaximal cycle protocol, on peak power and endurance cycling performance in well-trained cyclists. METHODS: Seventeen well-trained competitive male road racing cyclists completed four peak power output (PPO) tests and four 40-km time trials (40-km TT). Before each test, all cyclists performed a novel submaximal cycle test (Lamberts and Lambert Submaximal Cycle Test (LSCT)). Parameters associated with performance such as power, speed, cadence and rating of perceived exertion (RPE) were measured during the three stages of the test when cyclists rode at workloads coinciding with fixed predetermined heart rates. Heart rate recovery (HRR) was measured after the last stage of the test. RESULTS: Parameters measured during the second and third stages of the LSCT were highly reliable (intraclass correlation range: R=0.85-1.00) with low typical error of measurements (range: 1.3-4.4%). Good relationships were found between the LSCT and cycling performance measured by the PPO and 40-km TT tests. Mean power had stronger relationships with measures of cycling performance during the second (r=0.80-0.89) and third stages (r=0.91-0.94) of the LSCT than HRR (r=0.55-0.68). CONCLUSIONS: The LSCT is a reliable novel test which is able to predict peak and endurance cycling performance from submaximal power, RPE and HRR in well-trained cyclists. As these parameters are able to detect meaningful changes more accurately than VO(2max), the LSCT has the potential to monitor cycling performance with more precision than other current existing submaximal cycle protocols.

Heart rate recovery as a guide to monitor fatigue and predict changes in performance parameters.

Determining the optimal balance between training load and recovery contributes to peak performance in well-trained athletes. The measurement of heart rate recovery (HRR) to monitor this balance has become popular. However, it is not known whether the impairment in performance, which is associated with training-induced fatigue, is accompanied by a change in HRR. Therefore, the aim of this study was to retrospectively analyze the relationship between changes in HRR and cycling performance in a group of well-trained cyclists (n=14) who participated in a 4-week high-intensity training (HIT) program. Subjects were assigned to either a group that continuous had a increase in HRR (G(Incr)) or a group that showed a decrease in HRR (G(Decr)) during the HIT period. Both groups, G(Incr) and G(Decr), showed improvements in the relative peak power output (P=0.001 and 0.016, respectively) and endurance performance parameters (P=0.001 and <0.048, respectively). The average power during the 40-km time trial (40-km TT), however, improved more in G(Incr) (P=0.010), resulting in a tendency for a faster 40-km TT time (P=0.059). These findings suggest that HRR has the potential to monitor changes in endurance performance and contribute to a more accurate prescription of training load in well-trained and elite cyclists.

Why it is difficult to detect an illegally bowled cricket delivery with either the naked eye or usual two-dimensional video analysis.

OBJECTIVE: In this study, the influence of various anatomical and biomechanical factors on the ability to detect the magnitude of elbow extension during the cricket bowling action, with either the naked eye or from conventional two-dimensional video footage was evaluated. DESIGN: Descriptive study SETTING: One male bowler who had a large carrying angle was studied by means of a three-dimensional biomechanical analysis using the Vicon MX13 motion analysis system when bowling at match pace. Photographs were taken from various angles during the bowling delivery action to illustrate factors influencing the visual appearance of an illegal delivery. MAIN OUTCOME MEASURES: The influence of extension of the elbow joint and the elbow's anatomically fixed position, known as the "carrying angle", on the visual perception of an illegal ("thrown") delivery were the main outcome measures. RESULTS: The elbow joint rotates about 90 degrees as a result of humeral rotation during the movement of shoulder circumduction produced by the bowler's delivery action. This causes the plane in which the elbow joint moves to change throughout the delivery action. This movement will also vary between bowlers. The movement of elbow planar flexion/extension can be viewed only when the viewer's eyes are at exactly 90u to the plane of elbow joint movement. Thus, a cricket umpire wishing to detect elbow extension during the bowler's delivery action would need continuously to change his viewing position as the bowler's arm moved from the horizontal to the vertical position at ball release. We show that by viewing the action from only one position, the umpire will be confused by the illusion of a "throw" produced by a large "carrying angle" in some bowlers. CONCLUSION: It is impossible for an umpire conclusively to cite a bowler for an illegal action based only on naked eye observation. To do this the umpire would need to be in at least three different positions throughout a single delivery. Similarly, video footage shot from at least three different angles during the bowler's delivery action would need to be viewed by the match referee. By viewing the delivery from only one position, the visual illusion of a "throw" will be created by the presence of a large "carrying angle".

Sensitivity and specificity of clinical signs for assessment of dehydration in endurance athletes.

OBJECTIVE: To investigate the diagnostic accuracy of commonly used signs of dehydration in marathon runners. DESIGN: The diagnostic accuracy of 5 clinical signs/symptoms thought to indicate dehydration (altered skin turgor, dry oral mucous membranes, sunken eyes, an inability to spit and the sensation of thirst) was assessed by comparing the presence of these markers with the criterion standard of body weight change over a marathon footrace. SETTING: 2006 Auckland Marathon. PARTICIPANTS: 606 competitors in the full marathon. ASSESSMENT: Body weight was measured before and immediately after the marathon. The 5 clinical signs/symptoms were assessed immediately after the marathon. MAIN OUTCOME MEASURES: Diagnostic accuracy of clinical signs/symptoms to detect dehydration greater than 3% of body weight. Results 606 complete data sets were obtained. 3 clinical signs were associated with greater percentage weight loss: sunken eyes (mean percentage weight loss with symptom 2.6% (standard deviation 1.5), without 2.3% (1.5)); decreased skin turgor (with 3.0% (1.4), without 2.3% (1.5)) and the sensation of thirst (with 2.5% (1.5), without 2.3% (1.5)). The ability to spit and dry oral mucous membranes were unrelated to percentage weight loss. No signs/symptoms showed acceptably high validity for detecting a weight loss equal to or greater than 3% of body weight. CONCLUSIONS: The 5 parameters (decreased skin turgor, sensation of thirst, sunken eyes, inability to spit and dry mucous membranes) tested in this study did not precisely identify runners with total weight loss >3% at the end of a marathon.

Changes in plasma arginine vasopressin concentrations in cyclists participating in a 109-km cycle race.

OBJECTIVE: To evaluate the osmotic and non-osmotic regulation of arginine vasopressin (AVP) during endurance cycling. DESIGN: Observational study. Setting 109 km cycle race. PARTICIPANTS: 33 Cyclists. INTERVENTIONS: None. MAIN OUTCOME MEASUREMENTS: Plasma sodium concentration ([Na(+)]), plasma volume (PV) and plasma arginine vasopressin (AVP) concentration ([AVP](p)). RESULTS: A fourfold increase in [AVP](p) occurred despite a 2-mmol l(-1) decrease in plasma [Na(+)] combined with only modest (5%) PV contraction. A significant inverse correlation was noted between [AVP](p) Delta and urine osmolality Delta (r = -0.41, p<0.05), whereas non-significant inverse correlations were noted between [AVP](p) and both plasma [Na(+)] Delta and % PV Delta. Four cyclists finished the race with asymptomatic hyponatraemia. The only significant difference between the entire cohort with this subset of athletes was postrace plasma [Na(+)] (137.7 vs 133.5 mmol l(-1), p<0.001) and plasma [Na(+)] Delta (-1.9 vs -5.1 mmol l(-1), p<0.05). The mean prerace [AVP](p) of these four cyclists was just below the minimum detectable limit (0.3 pg ml(-1)) and increased marginally (0.4 pg ml(-1)) despite the decline in plasma [Na(+)]. CONCLUSIONS: The osmotic regulation of [AVP](p) during competitive cycling was overshadowed by non-osmotic AVP secretion. The modest decrease in PV was not the primary non-osmotic stimulus to AVP. Partial suppression of AVP occurred in four (12%) cyclists who developed hyponatraemia during 5 h of riding. Therefore, these results confirm that non-osmotic AVP secretion and exercise-associated hyponatraemia does, in fact, occur in cyclists participating in a 109 km cycle race. However, the stimuli to AVP is likely different between cycling and running.

Acute changes in arginine vasopressin, sweat, urine and serum sodium concentrations in exercising humans: does a coordinated homeostatic relationship exist?

The parallel response of sweat rate and urine production to changes in plasma osmolality and volume support a role for arginine vasopressin (AVP) as the main endocrine regulator of both excretions. A maximal test to exhaustion and a steady-state run on a motorised treadmill were both completed by 10 moderately trained runners, 1 week apart. Sweat, urine and serum sodium concentrations ([Na+]) were evaluated in association with the plasma concentrations of cytokines, neurohypophyseal and natriuretic peptides, and adrenal steroid hormones. When data from both the high-intensity and steady-state runs were combined, significant linear correlations were noted between: sweat [Na+] versus postexercise urine [Na+] (r=0.80; p<0.001), postexercise serum [Na+] versus both postexercise urine [Na+] (r=0.56; p<0.05) and sweat [Na+] (r=0.64; p<0.01) and postexercise urine [Na+] versus postexercise plasma arginine vasopressin concentration ([AVP](P)) (r=0.48; p<0.05). A significant positive correlation was noted between postexercise [AVP](P) and sweat [Na+] during the steady-state condition only (r=0.66; p<0.05). These correlations suggest that changes in serum [Na+] during exercise may evoke corresponding changes in sweat and urine [Na+], which are likely regulated coordinately by changes in [AVP](P) to preserve body fluid homeostasis.

Rates of fluid ingestion alter pacing but not thermoregulatory responses during prolonged exercise in hot and humid conditions with appropriate convective cooling.

The aim of the study was to examine the effects of fluid replacement on thermoregulation and cycling performance in hot, humid conditions. Six male cyclists (PPO = 426 +/- 39 W) performed six 80 km time trials. Subjects replaced 0% (0); 33% (33); 66% (66); or 100% (100) of the weight lost during an "ad libitum" trial (Ad Lib). In another condition (WET), subjects rinsed their mouths at 10 km intervals. There was no trial effect on any thermoregulatory variables or on performance. When WET, 0, 33 ("LO") were compared to Ad Lib; 66, 100 ("HI"), power output was higher in HI (209 +/- 22 vs. 193 +/- 22 W, p < 0.05). Restricting fluid below ad libitum rates impaired performance (LO group). Rates greater than ad libitum did not result in further improvements. Ad libitum fluid ingestion is optimal as it prevents athletes from ingesting too little or too much fluid.

The eccentric muscle loading influences the pacing strategies during repeated downhill sprint intervals.

The purpose was to compare self-chosen pace during ten repetitions of 60 m running sprints performed on a level surface (SPL), or when running uphill (SPU) or downhill (SPD) on a 4.7% slope. When expressed as percent of maximal running speed for corresponding condition, SPD was lower than SPL (95.28 +/- 1.93 vs. 97.31 +/- 1.29%; P = 0.044), which was lower than SPU (97.31 +/- 1.29 vs. 98.09 +/- 0.74%; P = 0.026). Heart rates, blood lactate concentrations and general perceived exertion were lower during SPD (163.8 +/- 8.3 bpm, 11.66 +/- 1.24 mmol L( -1), and 4.1 +/- 1.0) than SPL (169.8 +/- 7.8 bpm, 13.69 +/- 0.33 mmol L(-1), and 5.8 +/- 0.6), which were lower than SPU (174.9 +/- 8.7 bpm, 15.27 +/- 0.02, mmol L(-1), and 6.3 +/- 0.5) (P < 0.05 for all analyzes). Results show that the level of eccentric muscle loading influences the pacing strategy.

The physiological regulation of pacing strategy during exercise: a critical review.

The regulation of the pacing strategy remains poorly understood, because much of classic physiology has focused on the factors that ultimately limit, rather than regulate, exercise performance. When exercise is self-paced and work rate is free to vary in response to external and internal physiological cues, then a complex system is proposed to be responsible for alterations in exercise intensity, possibly through altered activation of skeletal muscle motor units. The present review evaluates the evidence for such a complex system by investigating studies in which interventions such as elevated temperature, altered oxygen content of the air, reduced fuel availability and misinformation about distance covered have resulted in alterations to the pacing strategy. The review further investigates how such a pacing strategy might be regulated for optimal performance, while ensuring that irreversible physiological damage is not incurred.

Which lap is the slowest? An analysis of 32 world mile record performances.

OBJECTIVES: The pacing strategies adopted by world-record breakers during the 1-mile footrace in order to evaluate different models for the biological basis of pacing was determined in this study. METHODS: Lap times in 32 world record performances were analysed. Average times for each of the four laps and as percentages of total race time were calculated. RESULTS: The slowest laps in 90% of races were either the second (34%) or the third (56%) laps. In only two (6%) records was the final lap the slowest, whereas in 24 (76%), it was either the fastest (38%) or the second fastest (38%) lap. Mean times for the second and third laps were both significantly slower than were times for the first or final laps, but there was no significant difference in times for the first and final lap. CONCLUSION: The finding that world record beaters run the final lap in their quickest mile races faster than the second and third laps matches findings for races at longer distances. The presence of this "end spurt" suggests that the pacing strategy is regulated "in anticipation" and is not purely the result of a developing "peripheral fatigue".

Exercising with reserve: evidence that the central nervous system regulates prolonged exercise performance.

OBJECTIVE: The purpose of this study was to measure the effects of an amphetamine (methylphenidate) on exercise performance at a fixed rating of perceived exertion of 16. METHODS: Eight elite cyclists ingested 10 mg methylphenidate in a randomised, placebo-controlled crossover trial. RESULTS: Compared with placebo, subjects receiving methylphenidate cycled for approximately 32% longer before power output fell to 70% of the starting value. At the equivalent time at which the placebo trial terminated, subjects receiving methylphenidate had significantly higher power outputs, oxygen consumptions, heart rates, ventilatory volumes and blood lactate concentrations although electromyographic activity remained unchanged. The ingestion of a centrally acting stimulant thus allowed subjects to exercise for longer at higher cardiorespiratory and metabolic stress indicating the presence of a muscular reserve in the natural state. CONCLUSIONS: This suggests that endurance performance is not only "limited" by mechanical failure of the exercising muscles ("peripheral fatigue"). Rather performance during prolonged endurance exercise under normal conditions is highly regulated by the central nervous system to ensure that whole-body homeostasis is protected and an emergency reserve is always present.

Exercising with reserve: exercise regulation by perceived exertion in relation to duration of exercise and knowledge of endpoint.

OBJECTIVE: The purpose of this study was to examine ratings of perceived exertion (RPE) and performance during repetitive maximal effort 40 km time trials as well as after an intervention that aimed to decrease certainty about the remaining distance of the exercise bout. In addition, we examined the RPE during exercise bouts of markedly different duration. METHODS: Part 1: 12 well-trained, competitive-level cyclists completed five 40 km time trials. During the final time trial all feedback was withheld until the final kilometre. In addition, to cause confusion about the remaining distance, they were asked to report their RPE at random intervals from 18 km to 38 km. Part 2: 6 well-trained, recreation-level cyclists randomly completed a 5 km, 10 km, 40 km and 100 km time trial. RESULTS: Part 1: Mean RPE increased during the first four trials and decreased during the final trial. The rate of RPE progression increased in linearity during the first four trials and became more conservative in the final trial. These changes were directly related to performance. Part 2: Mean RPE for longer duration trials (40 km, 100 km) were lower during the first half of trial duration but matched those of shorter trials in the final 20%. CONCLUSIONS: Increased familiarity of the exercise bout and certainty about its endpoint are associated with a more aggressive RPE strategy that produces a superior exercise performance. Certainty about the endpoint and the duration of exercise affect both the RPE strategy and performance.

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.