What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
A look at the medal podium in almost any international sporting competition reveals that some athletes and certain countries enjoy regular success in particular events. One of the most compelling examples is that of East African runners and their domination of international distance running competition. This phenomenon has led to the suggestion that East Africans possess some inherent genetic advantage predisposing them to superior athletic performances. The concurrent success of athletes of West African ancestry in sprint events appears to have augmented this belief.
Despite the speculation that African athletes have a genetic advantage, a report suggests there is no genetic evidence to date to suggest that this is the case, although research is at an early stage. The only available genetic studies of African athletes do not find that these athletes possess a unique genetic makeup; they serve to highlight the high degree of genetic diversity in East Africa and among elite East African athletes. Although genetic contributions to the phenomenal success of East Africans in distance running cannot be excluded, results to date implicate environmental factors.
A study investigated the effect on athletes exposed to 4 weeks of intermittent hypobaric hypoxia exposure (3 hours/day, 5 days/week at 4,000-5,500metres). Twenty-three collegiate level athletes were involved in the study. Apart from doubling EPO concentration 3 hours after hypoxia there was no other recorded physiological increases. Overall, the evidence from four independent measurement techniques suggested that intermittent hypobaric hypoxia exposure did not accelerate erythropoiesis (mature red blood cell production) despite the increase in serum EPO.
It is known that prior heavy exercise markedly alters the oxygen uptake ( O2) response to subsequent heavy exercise. However, the time required for O2 to return to its normal profile following prior heavy exercise is not known. A study examined the O2 responses to repeated bouts of heavy exercise separated by five different recovery durations. On separate occasions, nine male subjects completed two 6-minuste bouts of heavy cycle exercise separated by 10, 20, 30, 45, or 60 minutes of passive recovery. The second-by-second O2 responses were modelled. The study concluded that the priming effect of prior heavy exercise on the O2 response persists for at least 45 minutes, although the mechanism underpinning the effect remains obscure.
A study investigated the effects of ingesting a low (LGI) or high (HGI) glycaemic index carbohydrate (CHO) meal 3 hours prior to exercise on endurance running capacity. Eight male recreational runners undertook two trials (LGI or HGI) randomized and separated by 7 days. After an overnight fast (12 hours) the subjects ingested either a LGI or HGI meal 3 hours prior to running at 70% VO2 max until exhaustion. The meals contained 2g/kg body mass CHO and were isocaloric and iso-macronutrient with calculated GI values 77 and 37 for the HGI and LGI respectively. The run times for the LGI and HGI trials were 108.8 minutes and 101.4 minutes respectively. Fat oxidation rates were higher during exercise after the LGI meal than after the HGI meal. Ingestion of a LGI meal 3 hours before exercise resulted in an approximate 8% greater endurance capacity than after the ingestion of a HGI meal.
Another study assessed the knowledge, prevalence, and quantity of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Caffeine related questionnaires were self-administered to 140 international athletes. Fifty of these athletes further consented to immediate post-race blood samples for analysis of plasma caffeine. 72% of athletes correctly identified caffeine as being an unrestricted substance in triathlon. 89% of athletes were planning to use a caffeinated substance immediately prior to or throughout the race. Cola drinks (78%), caffeinated gels (42%), coffee (37%) and energy drinks (13%) were the most popular caffeinated choices. Mean ± standard deviation (and range) post-race plasma caffeine levels were 22.3 ± 20 µmol/L (1.7 to 98.4). Seven athletes (14%) finished with plasma caffeine levels = 40 µmol/L. Plasma values from elite athletes did not differ from age group competitors. Despite the prevalence of its consumption and the training experience of this athletic group, over one quarter of athletes remained either confused or uninformed about caffeine's legality. Levels of plasma caffeine taken immediately post-race indicated that athletes typically finish with quantities of caffeine that have been shown to improve endurance performance (i.e. 20 µmol/L or a dose of = 3 mg/kg body weight).
Seventeen subjects underwent cognitive (reaction time, number recall) and blood testing before and after consuming caffeine (6 mg/kg), placebo, or nothing (control) in a recent report. An exercise test (two 60 s maximal cycling bouts) was conducted 90 minutes after caffeine/placebo consumption. Plasma caffeine concentrations significantly increased after caffeine ingestion, however, there were no positive effects on cognitive or blood parameters except a significant decrease in plasma potassium concentrations at rest. Potentially negative effects of caffeine included significantly higher blood lactate compared to control and significantly slower time to peak power in exercise bout 2 compared to control and placebo. Caffeine had no significant effect on peak power, work output, RPE, or peak heart rate. In conclusion, caffeine had no ergogenic effect on repeated, maximal cycling bouts and may be detrimental to anaerobic performance.
A recent piece of research looked at the effects of exercise intensity on active and passive intestinal glucose absorption. Eight trained runners performed a 1 hour resting experiment and three 1-hour treadmill experiments at 30, 50, or 70% VO2 max in a temperature-controlled environment. Immediately prior to each experiment, normally hydrated subjects ingested a solution containing two glucose related substances that are not metabolized by the body: 3MG (actively absorbed; 5 g) and D-xylose (passively absorbed; 5 g). During the following 5 hours, all urine was collected and the amount of 3MG and D-xylose in the urine was determined. A significant reduction in urinary excretion of each carbohydrate was observed at 70% VO2 max compared to the other intensities suggesting that both active and passive intestinal absorption of glucose might be reduced during prolonged running at this intensity. This would appear to dilute the benefit to athletes of taking glucose alone during prolonged exercise.
A recent study examined the effect of downhill running on the autoimmune system through antibody responses (based on immunoglobulin). Eleven untrained men performed 2 x 60-minute bouts of downhill running (-13.5% gradient), at a speed eliciting 75% of their O2PEAK on a level grade. Two runs were spaced 14 days apart. Serum samples were collected before, after, and every hour for 12 hours and every 24 hours for six days. Serum total creatine kinase (the enzyme that helps remanufacture creatine phosphate for energy) and the immunoglobulins were measured. A significant interaction effect for creatine kinase (activity lower after run 2 than after run 1, 6-24 h) and exercise effect was observed with the serum concentrations of all immunoglobulins lower (except IgM) after run 2.
The lower antibody concentrations may reflect a reduced inflammatory response after run 2. The question in my mind is does this represent a measurable part of the overload / adaptation process?
Thirteen runners performed isokinetic muscle tests consisting of concentric and eccentric quadriceps and hamstring contractions on both legs three to four days before and 18 hours after a marathon in a recent paper. There were no significant differences between peak torque before and after the race, except that eccentric peak hamstring torque was reduced in both thighs. The authors concluded that over ground running (i.e. running a marathon) is associated with eccentric hamstring fatigue. Eccentric hamstring fatigue may be a potential risk factor for knee and soft tissue injuries during running. Eccentric hamstring training should therefore be introduced as an integral part of the training programme of runners.
The physiologic effects of whole-body vibration (WBV) have been widely studied. Recent research investigated whether a WBV program results in a better strength and postural control performance than an equivalent exercise program performed without vibration.
Thirty-three young competitive skiers (aged 9-15 years) underwent 6 weeks of training 3 times per week either with WBV or in an equivalent resistance (ER) group.
Torque, explosive strength (high box test), and postural control were assessed before and after the training period. Both training programs significantly improved isokinetic ankle and knee muscle strength and explosive strength. Moreover, the increases in explosive strength and in plantar-flexor strength at low speed were significantly higher in the WBV group than in the ER group after 6 weeks. However, neither WBV training nor ER training seemed to have an effect on postural control. The authors concluded that a strength-training program that includes WBV appears to have additive effects in young skiers compared with an equivalent program that does not include WBV. The findings support the hypothesis that WBV training may be a beneficial supplementary training technique in strength programs for young athletes.
Different dietary proteins have the potential to influence results obtained from resistance training. A study examined the effects of supplementation with two proteins, hydrolyzed whey isolate (WI) and casein (C), on strength, body composition, and plasma glutamine levels during a 10 week, supervised resistance-training program. 13 male, recreational bodybuilders supplemented their normal diet with either WI or C (1.5 gm/kg body wt/d) for the duration of the program. Strength was assessed by 1-RM in three exercises (barbell bench press, squat, and cable pull-down). Body composition and plasma glutamine levels were assessed in the week before and the week following 10 weeks of training. Plasma glutamine levels did not change in either supplement group following the intervention. The WI group achieved a significantly greater gain in lean mass than the C group (5kg vs. 0.8kg for WI and C, respectively) and a significant change in fat mass (-1.5kg) compared to the C group (+0.2kg). The WI group also achieved significantly greater improvements in strength compared to the C group in each assessment of strength. When the strength changes were expressed relative to body weight, the WI group still achieved significantly greater improvements in strength compared to the C group.
A study sought to evaluate the effectiveness of a preseason physical training programme that taught landing and falling skills in improving landing skills technique and preventing injury in junior elite Australian football players. 723 male players who participated in an under 18 elite competition were studied prospectively in a non-randomised controlled trial over two consecutive football seasons. There were 114 players in the intervention group and 609 control players. The eight-session intervention programme taught players six landing, falling, and recovery skills, which were considered fundamental for safe landing in Australian football. Landing skills taught in these sessions were independently rated for competence at baseline and mid-season. No significant differences between the groups were observed at baseline. Evaluation after the intervention revealed overall improvement in landing skills, but significantly greater improvement in the intervention group. Players in the intervention group were significantly less likely to sustain an injury during the season than the control group. In particular, the time to sustaining a landing injury was significantly less for the intervention group compared with the control group.
The study concluded that landing and falling ability could be taught to junior elite Australian football players. Players in the intervention group were protected against injury, particularly injuries related to landing and falls.
The B-vitamins (thiamin, riboflavin, and vitamin B-6) are necessary in the energy producing pathways of the body, while folate and vitamin B-12 are required for the synthesis of new cells, such as the red blood cells, and for the repair of damaged cells. Active individuals with poor or marginal nutritional status for a B-vitamin may have decreased ability to perform exercise at high intensities. A review focused on the B-vitamins and their role in energy metabolism and cell regeneration. Current research suggests that exercise may increase the requirements for riboflavin and vitamin B-6, while data for folate and vitamin B-12 are limited. Athletes who have poor diets, especially those restricting energy intakes or eliminating food groups from the diet, should consider supplementing with a multivitamin/mineral supplement.
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About the Author
Nigel Hetherington was the Head Track & Field Coach at the internationally acclaimed Singapore Sports School. He is a former National Performance Development Manager for Scottish Athletics and National Sprints Coach for Wales. Qualified and highly active as a British Athletics level 4 performance coach in all events he has coached athletes to National and International honours in sprints, hurdles as well as a World Record holder in the Paralympic shot. He has 10 years' experience as senior coach educator and assessor trainer on behalf of British Athletics. Nigel is also an experienced athlete in sprint (World Masters Championship level) and endurance (3-hour marathon runner plus completed the 24 hour 'Bob Graham Round' ultra-endurance event up and down 42 mountain peaks in the English Lake District). He is a chartered chemist with 26 years' experience in scientific research and publishing.
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