What the experts say

Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology, and athletic development.

'The act, quality, or power of withstanding hardship or stress'

Though classically thought of as referring to aerobic fitness, even in sport 'endurance' can be suffixed to many other words, for example: 'speed', 'strength', 'psychological' (mental) all of which may play a role in both in a sustained, mainly aerobic, activity such as marathon running, cross-country skiing, 90 minutes of football, etc. or else provide an important endurance component to some much shorter time-framed activity such as speed endurance for 200m running, the strength endurance for a series of continuous rugby encounters or the mental endurance for 100 shots at a target in archery. Even 'simple' aerobic fitness is affected by a multitude of factors including lung function, heart stroke volume, blood oxygen-carrying capacity, muscle function and energy stores, hydration, and so on. Furthermore, from a long-term goal-setting perspective, the endurance of both coach and athlete will be severely tested many times as the years go by. It may be important to be aware of 'endurance' in these various forms. This month's review covers an array of reports based on many of these factors.

Masters are getting better

Recent literature highlights the fact that master athletes (both men and women) are enduring! A study^[1] shows that for all 415,000 competitors in the New York City Marathon, over the period 1983-1999, the master athletes endured the best and showed improved running times even relative to their younger counterparts. Since the belief is that physical activity may slow the ageing process, this may mean that masters are now getting younger.

Trainability is not affected by initial VO₂ max! - Hope for us all?

At the other end of the scale a study based on adolescent Kenyan males^[2] found, quite convincingly, that although a scientifically selected group of boys from a 'village' environment were initially 'fitter' (VO₂ max) and faster (5k time trial) than an equally carefully selected group of 'town' boys, from nearby and living at the same altitude, there was no statistically significant difference in their overall trainability over 12 weeks. The village boys started ahead and finished ahead. The report concludes that the initially higher VO₂ max figure was the primary reason for the margin. Village boys improved from 56.0 to 59.1 while town boys increased from 50.3 to 55.6 (all ml kg-1 min-1). No reason for the initially higher values in the village boys was given though presumably, lifestyle may have played a significant part rather than a specific genetic factor. It would be very revealing for this study to be continued to establish if the town boys could match the village boys through continued training.

Another important factor in endurance is energy cost. A paper^[3] iidentified that in comparing positively, and non-trained runners that the overall energy cost of running was the same in all three classes (as measured using pulmonary gas exchange). Highly well-trained athletes are better conditioned and will be able to harvest and utilize more oxygen. However, internal mechanical and potential energy measurements did reveal a reduction for highly trained athletes with the suggestion that this is related to impact loads, i.e. foot-plant biomechanics.

Aerobic training benefits speed merchants

Moving up a gear a study^[4] has identified the relevance of aerobic metabolism in maximal speed endurance. Based on cycle ergometer sprints subjects completed either a 10s or 20s maximum sprint followed by 2 minutes of rest than a 30s maximum sprint. Overall the findings indicated that although ATP turnover from anaerobic sources was reduced by around 51% during the second half of a 20s sprint, the actual power output only decreased by 28% due to a twofold increase in aerobic energy contribution from 13 to 27% of total ATP turnover. This served to compensate for the reduction in the anaerobic pathway partially. Though we are not sure as to the level of anaerobic conditioning, these individuals may have attained beforehand, it still is a compelling argument for increasing the aerobic content of training for anaerobic athletes. Performance in the 30s sprint was least affected by the 10s sprint beforehand over the 20s sprint probably as a consequence of higher muscle acidosis following the 20s sprint.

Lab data does predict performance

Predicting endurance performance is always useful for coach and athlete and VO₂ max (i.e. the maximum volume of oxygen, measured in ml, that can be used per kg of body weight per minute) is a frequently reported yardstick here. A study from Scandinavia^[5] looked at an array of measurements made in a treadmill situation and then compared these to actual competition performances and rankings for 16 cross-country skiers (7 male, 9 female). For the male subjects, a high value for the onset of blood lactate accumulation (OBLA, 4mmol l-1) was related to a good performance ranking position. For women, the best association was through the respiratory exchange ratio (i.e. CO2 produced to O2 consumed). Oxygen consumption (expressed as l min-1) was most meaningful for both male and female skiers in predicting race results. These findings strongly support the use of appropriate 'lab tests' for performance prediction and, though not stated, are also highly relevant to monitoring improvements brought about through specific training that will result in better race performances.

An interesting study^[6] looked at so-called muscle power factors - peak velocity, blood lactate concentration (BLA), and 30m run velocity - and compared them to VO₂ max as measures of horizontal and uphill running performance. The report concluded that VO₂ max contributed more to uphill running performance than horizontal running.

Masters…keep going to keep on going!

Since oxygen consumption is inextricably linked to endurance performance, it is particularly enlightening to view a recent paper^[7] that looked at the decay of VO₂ max in older men. The study looked at trained and untrained men of retirement age and followed various regimes ranging from maintenance of activity for a high training group through to an inactive group remaining sedentary. The conclusions from the work were that loss of VO₂ max would occur with age at a linear rate with sedentary males but that 'vigorously' trained males could retain their values.

Aerobic training tops for health benefits

Always on the agenda these days is the impact of aerobic exercise on health. A recent study^[8] looked at the effect of this on sedentary young men and women. The study found that after just six weeks that there were measurable improvements in VO₂ max, whereas the control group did not change. Similarly, the trained subjects retained lower heart rates after an aerobic experiment and subsequently had lower resting pulses. Lower heart rates were also witnessed following a psychological shock. Broader experience also links aerobic training directly to a better ability to protect against age-related coronary heart disease. Though a third group showed measurable aerobic improvement from a weight training only regime (about 50% of that of the aerobically trained group), this was thought to relate to improvement in leg performance. So it could also postulate that power athletes may benefit health-wise in the long term from increased levels of aerobic exercise.

Keeping your finger on the pulse

Many coaches and athletes advocate the taking of pulse rate immediately post-exercise as a means of recording the training effort objectively in terms of % of maximum heart rate (HR). Unfortunately, a recent study^[9] demonstrated that due to the rapid recovery of HR following exercise bouts pulse checks made post-exercise might underestimate HR by as much as 20-27 bpm. This sounds like a good argument for the use of a heart-rate monitor during exercise or for a correction factor to be applied afterward. Pulse rates taken after exercise remain useful for monitoring recovery objectively.

Mix those carbohydrates for a greater energy boost

Energy replenishment during endurance activities plays a significant part in maintaining output. So it was intriguing to read a report^[10] that examined the comparative benefits of consuming a single carbohydrate (CHO) as an energy source versus a CHO mixture. The work started with the premise that consuming a mixture of glucose and sucrose or glucose and fructose, at a high rate (1.8g min-1) resulted in a 20-55% higher oxidation rate (1.3g min-1) compared with ingestion of just glucose at the same calorific rate. The latest work by the same group looked at three-component mixtures of the sugars mentioned above at even higher rates (2.4g min-1). The results point to an even higher oxidation rate (1.7g min-1) during 150min cycle rides at 62% VO₂ max. A complementary study^[11] looked at glucose infusion (1g min-1) during a 1-hour time trial working at the same VO₂ max as the study above. The results demonstrated that glucose infusion did not affect the time-trial performance, despite the increased availability of plasma glucose for oxidation and evidence of increased glucose uptake into the tissues. The reason for this is that the endogenous CHO stores were not exhausted during the trial and so the 'top-up' was not necessary.

More on hydration effects

In Successful Coaching, Issue 12, the potentially dangerous effects of hyponatraemia were discussed. A very recent case report^[12] on the South African Ironman Triathlon provides a very poignant reminder of this condition. Based on 371 athletes (62% of all finishers) the athlete who gained the most weight (3.6kg) during the event was the only athlete to develop symptomatic hyponatraemia. During recovery, he excreted an excess of 4.6 litres of urine. Athletes need to guard against excessive water intake (dipsomania). On the subject of hydration and endurance exercise, a further report^[13] from the same group concluded that there was no clinically significant change in serum electrolyte levels and no change in hydration status in runners who experience exercise-associated muscle cramping during ultra-distance running. This was based on the study of 72 runners and involved tracking blood levels of a series of markers before, immediately after, and 60mins after the race.

From Ironman to iron in man

Transport of oxygen in the blood is facilitated by iron-containing haemoglobin, and many endurance athletes seek to ensure this pathway is maximized by supplementing their diet with iron. However, the latest findings^[14] suggest that athletes tempted to take iron supplements are well-advised to have their iron levels checked first. A condition known as hereditary haemochromotosis that affects iron metabolism can induce iron overload, potentially leading to organ dysfunction. In a study of 65 highly trained athletes' possible genetic mutations that may cause this condition was found in half the cases! Thankfully, none had the disease, but the potential seemed to be there. Altitude training is famed for elevating oxygen-carrying potential by increasing the number of red blood cells. However, intermittent bouts of exposure to high altitudes appear not to be of benefit. A study^[15] based on 2-hour exposure to 4100m altitude conditions in a hypobaric chamber each day for 14 days showed no change in blood indicators or any improvement in performance during a submaximal cycle ergometer test.

More on heart rate monitors

Finally, back to heart rate monitors and their potential for use in estimating the energy cost of exercise. A study^[16] has highlighted that use of such devices can provide rough estimates of energy expenditure during running, rowing, or cycling when predicted values of VO₂ max and HR_max are used. When actual measured values for these parameters were used errors in values were further reduced although energy expenditure for females still showed a 12% over-estimation. Hope reading this did not require too much endurance!!

Article Reference

This article first appeared in:

HETHERINGTON, N. (2004) What the experts say. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 16 / October), p. 12-14

References

Jokl, P et al. 'Master's performance in the New York City Marathon 1983-1999' Br J Sports Med 38, (2004) 408-412
Larsen, Henrik B et al. 'Training response of adolescent Kenyan town and village boys to endurance running' Scandinavian Journal of Medicine & Science in Sports
Slawinski, Jean S and Billat, Veronique L 'Difference in Mechanical and Energy Cost between Highly, Well, and Non-trained Runners' Medicine & Science in Sports & Exercise. 36(8) (Aug 2004) 1440-1446
Bogdanis, GC et al. 'Power output and muscle metabolism during and following recovery from 10 and 20 s of maximal sprint exercise in humans' Acta Physiologica Scandinavica 163 (3), (1998) 261-272
Larsson, P et al. 'Physiological predictors of performance in cross-country skiing from treadmill tests in male and female subjects' Scandinavian Journal of Medicine & Science in Sports 12 (6), (2002) 347-353
Paavolainen, L et al. 'Muscle power factors and VO₂ max as determinants of horizontal and uphill running performance' Scandinavian Journal of Medicine & Science in Sports 10 (5), (2000) 286-291
Katzel, Leslie I et al. 'A Comparison of Longitudinal Changes in Aerobic Fitness in Older Endurance Athletes and Sedentary Men' Journal of the American Geriatrics Society 49 (12), (2001) 1657-1664
Spalding, Thomas W et al. 'Aerobic exercise training and cardiovascular reactivity to psychological stress in sedentary young normotensive men and women' Psychophysiology 41 (4), (2004) 552-562.
DeVan, Allison E et al. 'Post-exercise palpation of pulse rates: its applicability to habitual exercisers' Scandinavian Journal of Medicine & Science in Sports, Online Early (2004)
Jentjens, Roy LPG et al. 'High Oxidation Rates from Combined Carbohydrates Ingested during Exercise' Medicine & Science in Sports & Exercise. 36(9), (Sep 2004) 1551-1558
Carter, JM et al. 'The Effect of Glucose Infusion on Glucose Kinetics during a 1-h Time Trial' Med Sci Sports Exerc, 36, 9, (2004) 1543-1550
Noakes TD et al. 'The dipsomania of great distance: water intoxication in an Ironman triathlete' Br J Sports Med 38, (2004) e16 (online)
Schwellnus MP et al. 'Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners' Br J Sports Med 38, (2004) 488-492
Chicharro JL et al. 'Mutations in the hereditary haemochromatosis gene HFE in professional endurance athletes' Br J Sports Med 38, (2004) 418-421
Lundby C et al. 'The influence of intermittent altitude exposure to 4100m on exercise capacity and blood variables' Scandinavian Journal of Medicine & Science in Sports, Online Early (2004)
Crouter, SE et al. 'Accuracy of Polar S410 Heart Rate Monitor to Estimate Energy Cost of Exercise' Med Sci Sports Exerc, 36, 8, (2004) 1433-1439

Page Reference

If you quote information from this page in your work, then the reference for this page is:

HETHERINGTON, N. (2004) What the experts say [WWW] Available from: https://www.brianmac.co.uk/articles/scni16a8.htm [Accessed

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 ten years of experience as a 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 of experience in scientific research and publishing.


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'The act, quality, or power of withstanding hardship or stress' Though classically thought of as referring to aerobic fitness, even in sport 'endurance' can be suffixed to many other words, for example: 'speed', 'strength', 'psychological' (mental) all of which may play a role in both in a sustained, mainly aerobic, activity such as marathon running, cross-country skiing, 90 minutes of football, etc. or else provide an important endurance component to some much shorter time-framed activity such as speed endurance for 200m running, the strength endurance for a series of continuous rugby encounters or the mental endurance for 100 shots at a target in archery. Even 'simple' aerobic fitness is affected by a multitude of factors including lung function, heart stroke volume, blood oxygen-carrying capacity, muscle function and energy stores, hydration, and so on. Furthermore, from a long-term goal-setting perspective, the endurance of both coach and athlete will be severely tested many times as the years go by. It may be important to be aware of 'endurance' in these various forms. This month's review covers an array of reports based on many of these factors. Masters are getting better Recent literature highlights the fact that master athletes (both men and women) are enduring! A study^[1] shows that for all 415,000 competitors in the New York City Marathon, over the period 1983-1999, the master athletes endured the best and showed improved running times even relative to their younger counterparts. Since the belief is that physical activity may slow the ageing process, this may mean that masters are now getting younger. Trainability is not affected by initial VO₂ max! - Hope for us all? At the other end of the scale a study based on adolescent Kenyan males^[2] found, quite convincingly, that although a scientifically selected group of boys from a 'village' environment were initially 'fitter' (VO₂ max) and faster (5k time trial) than an equally carefully selected group of 'town' boys, from nearby and living at the same altitude, there was no statistically significant difference in their overall trainability over 12 weeks. The village boys started ahead and finished ahead. The report concludes that the initially higher VO₂ max figure was the primary reason for the margin. Village boys improved from 56.0 to 59.1 while town boys increased from 50.3 to 55.6 (all ml kg-1 min-1). No reason for the initially higher values in the village boys was given though presumably, lifestyle may have played a significant part rather than a specific genetic factor. It would be very revealing for this study to be continued to establish if the town boys could match the village boys through continued training. Another important factor in endurance is energy cost. A paper^[3] iidentified that in comparing positively, and non-trained runners that the overall energy cost of running was the same in all three classes (as measured using pulmonary gas exchange). Highly well-trained athletes are better conditioned and will be able to harvest and utilize more oxygen. However, internal mechanical and potential energy measurements did reveal a reduction for highly trained athletes with the suggestion that this is related to impact loads, i.e. foot-plant biomechanics. Aerobic training benefits speed merchants Moving up a gear a study^[4] has identified the relevance of aerobic metabolism in maximal speed endurance. Based on cycle ergometer sprints subjects completed either a 10s or 20s maximum sprint followed by 2 minutes of rest than a 30s maximum sprint. Overall the findings indicated that although ATP turnover from anaerobic sources was reduced by around 51% during the second half of a 20s sprint, the actual power output only decreased by 28% due to a twofold increase in aerobic energy contribution from 13 to 27% of total ATP turnover. This served to compensate for the reduction in the anaerobic pathway partially. Though we are not sure as to the level of anaerobic conditioning, these individuals may have attained beforehand, it still is a compelling argument for increasing the aerobic content of training for anaerobic athletes. Performance in the 30s sprint was least affected by the 10s sprint beforehand over the 20s sprint probably as a consequence of higher muscle acidosis following the 20s sprint. Lab data does predict performance Predicting endurance performance is always useful for coach and athlete and VO₂ max (i.e. the maximum volume of oxygen, measured in ml, that can be used per kg of body weight per minute) is a frequently reported yardstick here. A study from Scandinavia^[5] looked at an array of measurements made in a treadmill situation and then compared these to actual competition performances and rankings for 16 cross-country skiers (7 male, 9 female). For the male subjects, a high value for the onset of blood lactate accumulation (OBLA, 4mmol l-1) was related to a good performance ranking position. For women, the best association was through the respiratory exchange ratio (i.e. CO2 produced to O2 consumed). Oxygen consumption (expressed as l min-1) was most meaningful for both male and female skiers in predicting race results. These findings strongly support the use of appropriate 'lab tests' for performance prediction and, though not stated, are also highly relevant to monitoring improvements brought about through specific training that will result in better race performances. An interesting study^[6] looked at so-called muscle power factors - peak velocity, blood lactate concentration (BLA), and 30m run velocity - and compared them to VO₂ max as measures of horizontal and uphill running performance. The report concluded that VO₂ max contributed more to uphill running performance than horizontal running. Masters…keep going to keep on going! Since oxygen consumption is inextricably linked to endurance performance, it is particularly enlightening to view a recent paper^[7] that looked at the decay of VO₂ max in older men. The study looked at trained and untrained men of retirement age and followed various regimes ranging from maintenance of activity for a high training group through to an inactive group remaining sedentary. The conclusions from the work were that loss of VO₂ max would occur with age at a linear rate with sedentary males but that 'vigorously' trained males could retain their values. Aerobic training tops for health benefits Always on the agenda these days is the impact of aerobic exercise on health. A recent study^[8] looked at the effect of this on sedentary young men and women. The study found that after just six weeks that there were measurable improvements in VO₂ max, whereas the control group did not change. Similarly, the trained subjects retained lower heart rates after an aerobic experiment and subsequently had lower resting pulses. Lower heart rates were also witnessed following a psychological shock. Broader experience also links aerobic training directly to a better ability to protect against age-related coronary heart disease. Though a third group showed measurable aerobic improvement from a weight training only regime (about 50% of that of the aerobically trained group), this was thought to relate to improvement in leg performance. So it could also postulate that power athletes may benefit health-wise in the long term from increased levels of aerobic exercise. Keeping your finger on the pulse Many coaches and athletes advocate the taking of pulse rate immediately post-exercise as a means of recording the training effort objectively in terms of % of maximum heart rate (HR). Unfortunately, a recent study^[9] demonstrated that due to the rapid recovery of HR following exercise bouts pulse checks made post-exercise might underestimate HR by as much as 20-27 bpm. This sounds like a good argument for the use of a heart-rate monitor during exercise or for a correction factor to be applied afterward. Pulse rates taken after exercise remain useful for monitoring recovery objectively. Mix those carbohydrates for a greater energy boost Energy replenishment during endurance activities plays a significant part in maintaining output. So it was intriguing to read a report^[10] that examined the comparative benefits of consuming a single carbohydrate (CHO) as an energy source versus a CHO mixture. The work started with the premise that consuming a mixture of glucose and sucrose or glucose and fructose, at a high rate (1.8g min-1) resulted in a 20-55% higher oxidation rate (1.3g min-1) compared with ingestion of just glucose at the same calorific rate. The latest work by the same group looked at three-component mixtures of the sugars mentioned above at even higher rates (2.4g min-1). The results point to an even higher oxidation rate (1.7g min-1) during 150min cycle rides at 62% VO₂ max. A complementary study^[11] looked at glucose infusion (1g min-1) during a 1-hour time trial working at the same VO₂ max as the study above. The results demonstrated that glucose infusion did not affect the time-trial performance, despite the increased availability of plasma glucose for oxidation and evidence of increased glucose uptake into the tissues. The reason for this is that the endogenous CHO stores were not exhausted during the trial and so the 'top-up' was not necessary. More on hydration effects In Successful Coaching, Issue 12, the potentially dangerous effects of hyponatraemia were discussed. A very recent case report^[12] on the South African Ironman Triathlon provides a very poignant reminder of this condition. Based on 371 athletes (62% of all finishers) the athlete who gained the most weight (3.6kg) during the event was the only athlete to develop symptomatic hyponatraemia. During recovery, he excreted an excess of 4.6 litres of urine. Athletes need to guard against excessive water intake (dipsomania). On the subject of hydration and endurance exercise, a further report^[13] from the same group concluded that there was no clinically significant change in serum electrolyte levels and no change in hydration status in runners who experience exercise-associated muscle cramping during ultra-distance running. This was based on the study of 72 runners and involved tracking blood levels of a series of markers before, immediately after, and 60mins after the race. From Ironman to iron in man Transport of oxygen in the blood is facilitated by iron-containing haemoglobin, and many endurance athletes seek to ensure this pathway is maximized by supplementing their diet with iron. However, the latest findings^[14] suggest that athletes tempted to take iron supplements are well-advised to have their iron levels checked first. A condition known as hereditary haemochromotosis that affects iron metabolism can induce iron overload, potentially leading to organ dysfunction. In a study of 65 highly trained athletes' possible genetic mutations that may cause this condition was found in half the cases! Thankfully, none had the disease, but the potential seemed to be there. Altitude training is famed for elevating oxygen-carrying potential by increasing the number of red blood cells. However, intermittent bouts of exposure to high altitudes appear not to be of benefit. A study^[15] based on 2-hour exposure to 4100m altitude conditions in a hypobaric chamber each day for 14 days showed no change in blood indicators or any improvement in performance during a submaximal cycle ergometer test. More on heart rate monitors Finally, back to heart rate monitors and their potential for use in estimating the energy cost of exercise. A study^[16] has highlighted that use of such devices can provide rough estimates of energy expenditure during running, rowing, or cycling when predicted values of VO₂ max and HR_max are used. When actual measured values for these parameters were used errors in values were further reduced although energy expenditure for females still showed a 12% over-estimation. Hope reading this did not require too much endurance!! Article Reference This article first appeared in: HETHERINGTON, N. (2004) What the experts say. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 16 / October), p. 12-14 References Jokl, P et al. 'Master's performance in the New York City Marathon 1983-1999' Br J Sports Med 38, (2004) 408-412 Larsen, Henrik B et al. 'Training response of adolescent Kenyan town and village boys to endurance running' Scandinavian Journal of Medicine & Science in Sports Slawinski, Jean S and Billat, Veronique L 'Difference in Mechanical and Energy Cost between Highly, Well, and Non-trained Runners' Medicine & Science in Sports & Exercise. 36(8) (Aug 2004) 1440-1446 Bogdanis, GC et al. 'Power output and muscle metabolism during and following recovery from 10 and 20 s of maximal sprint exercise in humans' Acta Physiologica Scandinavica 163 (3), (1998) 261-272 Larsson, P et al. 'Physiological predictors of performance in cross-country skiing from treadmill tests in male and female subjects' Scandinavian Journal of Medicine & Science in Sports 12 (6), (2002) 347-353 Paavolainen, L et al. 'Muscle power factors and VO₂ max as determinants of horizontal and uphill running performance' Scandinavian Journal of Medicine & Science in Sports 10 (5), (2000) 286-291 Katzel, Leslie I et al. 'A Comparison of Longitudinal Changes in Aerobic Fitness in Older Endurance Athletes and Sedentary Men' Journal of the American Geriatrics Society 49 (12), (2001) 1657-1664 Spalding, Thomas W et al. 'Aerobic exercise training and cardiovascular reactivity to psychological stress in sedentary young normotensive men and women' Psychophysiology 41 (4), (2004) 552-562. DeVan, Allison E et al. 'Post-exercise palpation of pulse rates: its applicability to habitual exercisers' Scandinavian Journal of Medicine & Science in Sports, Online Early (2004) Jentjens, Roy LPG et al. 'High Oxidation Rates from Combined Carbohydrates Ingested during Exercise' Medicine & Science in Sports & Exercise. 36(9), (Sep 2004) 1551-1558 Carter, JM et al. 'The Effect of Glucose Infusion on Glucose Kinetics during a 1-h Time Trial' Med Sci Sports Exerc, 36, 9, (2004) 1543-1550 Noakes TD et al. 'The dipsomania of great distance: water intoxication in an Ironman triathlete' Br J Sports Med 38, (2004) e16 (online) Schwellnus MP et al. 'Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners' Br J Sports Med 38, (2004) 488-492 Chicharro JL et al. 'Mutations in the hereditary haemochromatosis gene HFE in professional endurance athletes' Br J Sports Med 38, (2004) 418-421 Lundby C et al. 'The influence of intermittent altitude exposure to 4100m on exercise capacity and blood variables' Scandinavian Journal of Medicine & Science in Sports, Online Early (2004) Crouter, SE et al. 'Accuracy of Polar S410 Heart Rate Monitor to Estimate Energy Cost of Exercise' Med Sci Sports Exerc, 36, 8, (2004) 1433-1439 Page Reference If you quote information from this page in your work, then the reference for this page is: HETHERINGTON, N. (2004) What the experts say [WWW] Available from: https://www.brianmac.co.uk/articles/scni16a8.htm [Accessed 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 ten years of experience as a 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 of experience in scientific research and publishing.