What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology, and athletic development.
Times of the top six finishers in a total of 283 men's and women's Olympic and world championship running, swimming, and speed skating finals held between 1952 and 2006 were analysed, and performance differences between males and females were calculated for each final position in three sporting events
After a relatively faster rate of improvement among females from the 1950s to a nadir in the 1980s, the gender difference in anaerobic performance at the highest levels of international competition has increased during the last 15yr. Overall, the time-based performance difference for all six events analysed has increased from a low of 10.3% in the period 1976-1988 to a current difference of 11.5% for the period 2000-2005. Analysis of elite sprinting performance during the last 50yr reveals that the performance difference between males and females has ceased to narrow and has widened since the mid-1990s. The change observed cannot be explained by declining women's participation in sports, poorer training practice, or reduced access to technological developments. Still, it does coincide with dramatic improvements in the scope and sensitivity of drug testing. Current gender differences in performance and the underlying differences in performance power may now reasonably reflect the actual physiological differences between males and females.
A study examined the effects of two popular dietary supplements-whey protein (WP) and creatine monohydrate (CrM) (both separately and in combination)-on body composition, muscle strength, fibre-specific hypertrophy (i.e. type I, IIa, IIx), and contractile protein accrual during resistance (RE) training.
In a double-blind, randomized protocol, resistance-trained males were matched for strength and placed into one of four groups: creatine/carbohydrate (CrCHO), creatine/whey protein (CrWP), WP only, or carbohydrate only (CHO) (1.5g/kg body weight per day). All assessments were completed the week before and after an 11-wk structured, supervised RE program. Assessments included strength (1RM, three exercises), body composition, and vastus lateralis muscle biopsies for determination of muscle fibre type, cross-sectional area (CSA), contractile protein, and creatine (Cr) content.
Supplementation with CrCHO, WP, and CrWP resulted in significantly greater 1RM strength improvements (three of three assessments) and muscle hypertrophy compared with CHO. Up to 76% of the strength improvements in the squat could be attributed to hypertrophy of muscle involved in this exercise. However, the hypertrophy responses within these groups varied at the three levels assessed (i.e., changes in lean mass, fibre-specific hypertrophy, and contractile protein content). Although WP or CrM seemed to promote greater strength gains and muscle morphology during RE training, the hypertrophy responses within the groups varied. These differences may have important implications for the coaching of individual athletes in resistance training.
The effects of oral ß-hydroxy-ß-methylbutyrate (HMB) supplementation (3 g/d) on selected components of aerobic performance and body composition of active college students were studied. For a 5-wk supplementation period subjects underwent interval training three times a week on a treadmill. Respiratory factors and body composition were determined. Significant differences were observed between the two groups in gains in maximal oxygen consumption (+8.4% PLA vs +15.5% HMB) and in respiratory-compensation point (+8.6% PLA vs +13.4% HMB) suggesting that HMB supplementation positively affects selected components of aerobic performance. Body composition was unchanged.
Researchers examined the effects of combined creatine (Cr) and glycerol (Gly) supplementation on responses to exercise in the heat. Subjects were assigned to either a Cr or placebo (Pl) group. Twice daily during two 7-d supplementation regimens, the Cr group received 11.4g of Cr·H2O, and the Pl group received 11.4g of glucose. Subjects in both groups also ingested 1g of Gly/kg body mass (twice daily) in either the first or the second supplementation regimen. This design allowed 4 combinations of supplements to be examined (Pl/Pl, Pl/Gly, Cr/Pl, and Cr/Gly). Exercise trials were conducted pre and post-supplementation at 30°C and 70% relative humidity. In the Pl group, total body water (TBW) increased by averages of 0.50L after Gly and in the Cr group by 0.63L after Pl and by 0.87L after Gly. Both Cr/Pl and Cr/Gly resulted in significantly attenuated heart rate, rectal temperature, and perceived effort during exercise, although no regimen had any effect on performance. The addition of Gly to Cr significantly increased TBW more than Cr alone but did not further enhance the attenuation in HR, Tre, and RPE during exercise. These data suggest that combined Cr and Gly is an effective method of hyperhydration capable of reducing thermal and cardiovascular responses.
Comparison of protein intakes on strength, body composition, and hormonal changes was examined in experienced strength/power athletes participating in a 12-week resistance training program. Three groups were established depending upon their daily consumption of protein; below recommended levels (BL; 1.0-1.4g/kg/day), recommended levels (RL; 1.6-1.8g/kg/day) and above recommended levels (AL; > 2.0g/kg/day). Subjects were assessed for strength (1-RM) bench press/squat and body composition. Resting blood samples were analysed for total testosterone, cortisol, growth hormone, and insulin-like growth factor. No differences were seen in energy intake (3,171 ± 577 Calories) between the groups, and the energy intake for all groups was also below the recommended levels for strength/power athletes. No significant changes were seen in body mass, lean body mass, or fat mass in any group. Significant improvements in 1-RM bench press and 1-RM squat were seen in all three groups, however, no differences between the groups were observed. No significant changes were determined in 1RM or seen in resting hormonal concentrations. The results of this study do not provide support for protein intakes greater than recommended levels for body composition improvements, or alterations in resting hormonal concentrations.
A paper reported on the effects of post-exercise carbohydrate-protein-antioxidant (CHO+P+A) ingestion on plasma creatine kinase (CK), muscle soreness, and subsequent cross-country race performance. Runners consumed 10 mL/kg body weight of CHO or CHO+P+A beverage immediately after each training session for 6-d before a cross-country race. After a 21-d washout period, subjects repeated the protocol with the alternate beverage. Post-intervention CK and soreness were significantly lower after CHO+P+A (223.21U/L) intervention than after CHO (307.3U/L), despite no differences in baseline measures. There were no overall differences in running performance after CHO and CHO+P+A interventions. There were, however, significant correlations between treatment differences and running mileage, with higher mileage runners having trends toward improved attenuations in CK and race performance after CHO+P+A intervention than lower mileage runners. Muscle damage incurred during training appeared to be attenuated with post-exercise CHO+P+A ingestion, which leads to performance improvements in high-mileage runners.
Exercise training is known to induce an increase in free radical production, potentially leading to enhanced muscle injury. Vitamins C and E are well-known antioxidants that may prevent muscle cell damage. A study aimed to determine the effects of these supplemental antioxidant vitamins on markers of oxidative stress, muscle damage, and performance of elite soccer players. One group received vitamins C and E supplementation daily during the pre-competitive season (S group), while the placebo group (PL group) received a pill containing maltodextrin. Both groups performed the same training load during the three-month pre-season training period. Erythrocyte antioxidant enzymes glutathione reductase, catalase, and plasma carbonyl derivatives did not show any significant variation among the experimental groups. Similarly, fitness level markers did not differ among the experimental groups. However, the S group demonstrated lower lipid peroxidation and muscle damage levels compared to PL group at the final phase of the pre-competitive season. The data demonstrated that vitamin C and E supplementation in soccer players might reduce lipid peroxidation and muscle damage during high-intensity efforts but did not enhance performance.
A study investigated the influence of low-dose bovine colostrum protein concentrate (CPC) supplementation on selected immune variables in cyclists. Highly trained male road cyclists completed an initial 40-km time trial (TT40). They were then randomly assigned to either a supplement (10g bovine CPC/day) or a placebo group (10 g whey protein concentrate/day). After 5 wk of supplementation, the cyclists completed a second TT40. They then completed 5 consecutive days of high-intensity training (HIT) that included a TT40, followed by a final TT40 in the following week. Venous blood and saliva samples were collected immediately before and after each TT40, and upper respiratory illness symptoms were recorded over the experimental period. From an array of biochemical/immune system marker measurements, it was concluded that low-dose bovine CPC supplementation modulates immune parameters during normal training and after an acute period of intense exercise, which may contribute to a trend toward reduced upper respiratory illness in the bovine CPC group.
Inspiring a hyperoxic (H) gas permits subjects to exercise at higher power outputs while training, but there is controversy as to whether this improves skeletal muscle oxidative capacity, maximal O2 consumption (O2 max), and endurance performance to a greater extent than training in normoxia (N). A study aimed to determine whether higher power output during H training leads to a greater increase in these parameters. Subjects were randomly assigned to train in H (60% O2) or N for 6 wk (3 sessions/wk of 10 x 4 min at 90% O2 max). Training heart rate (HR) was maintained during the study by increasing power output. After at least 6 wk of detraining, a second 6-wk training protocol was completed with the other breathing condition. O2 max and cycle time to exhaustion at 90% of pre-training O2 max were tested in room air pre and post training. Muscle biopsies were sampled pre- and post-training for various biochemical markers. Training power outputs were 8% higher (17 W) in H vs N. However, both conditions produced similar improvements in O2 max (11-12%); time to exhaustion (100%); and associated biochemistries. The authors concluded that the additional training stimulus provided by training in H was not sufficient to produce greater increases in the aerobic capacity of skeletal muscle and whole-body O2 max and exercise performance compared with training in N.
Researchers studied results and weather data for a range of marathons over the years. Results were broken into temperature quartiles (Q1 5.1-10°C, Q2 10.1-15°C, Q3 15.1-20°C, and Q4 20.1-25°C). Analysis of the top three male and female finishers as well as the 25th-, 50th-, 100th-, and 300th-place finishers were compared with the course record and then contrasted with the weather. Results: Marathon performances of top males were slower than the course record by 1.7 +/- 1.5, 2.5 +/- 2.1, 3.3 +/- 2.0, and 4.5 +/- 2.3% (mean +/- SD) for Q1-Q4, respectively. Differences between Q4, Q1, Q2, and Q3, and Q1 were statistically different. The top women followed a similar trend (Q1 3.2 +/- 4.9, Q2 3.2 +/- 2.9, Q3 3.8 +/- 3.2, and Q4 5.4 +/- 4.1%), but the differences among quartiles were not significant. The 25th-, 50th-, 100th-, and 300th-place finishers slowed more than faster runners as the temperature increased. The study demonstrated a progressive slowing of marathon performance as temperature increases from 5 to 25°C. This seems true for men and women of wide-ranging abilities. However, performance is more negatively affected for slower populations of runners.
A study examined the potential contributions of neuromuscular fatigue to non-contact anterior cruciate ligament (ACL) injuries prevalent in females. Athletes had 3D lower-limb-joint kinematics and kinetics recorded during 10 drop jumps, both before and after fatigue. Females landed with more initial ankle plantar flexion and peak-stance ankle supination, knee abduction, and knee internal rotation compared with men. They also had larger knee adduction, abduction, and internal rotation, and smaller ankle dorsiflexion moments. Fatigue increased initial and peak knee abduction and internal rotation motions and peak knee internal rotation, adduction, and abduction moments, with the latter being more pronounced in females. Researchers concluded that fatigue-induced modifications in lower-limb control might increase the risk of non-contact ACL injury during landings.
A study investigated whether pre-exercise sodium-bicarbonate ingestion improved judo-related performance. Performance evaluation was by three bouts of a specific judo test and four bouts of the Wingate test (WT) for upper limbs. Athletes ingested 0.3 g/kg of sodium bicarbonate or placebo 2 h before the tests. Blood lactate levels and perceived exertion were measured. Sodium bicarbonate improved performance in Bouts 2 and 3 of judo; mean power in Bouts 3 and 4 and peak power in Bout 4 of the WT. Ingestion of bicarbonate increased lactate concentration in judo but not in WT. Ratings of perceived exertion did not differ between treatments. Sodium bicarbonate improves judo-related performance and increases blood lactate concentration but has no effect on perceived exertion.
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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, and hurdles as well as a World Record holder in the Paralympic shot. He has ten years of experience as a senior coach educator and assessor trainer on behalf of British Athletics. Nigel is also an experienced athlete in the 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 of experience in scientific research and publishing.