Peter W.R. Lemon

Run Sprint Interval Training Improves Aerobic Performance but Not Maximal Cardiac Output

UNLABELLED Repeated maximal-intensity short-duration exercise (sprint interval training, SIT) can produce muscle adaptations similar to endurance training (ET) despite a much reduced training volume. However, most SIT data use cycling, and little is known about its effects on body composition or maximal cardiac output (Qmax). PURPOSE The purpose of this study was to assess body composition, 2000-m run time trial, VO(2max), and Q(max) effects of run SIT versus ET. METHODS Men and women (n = 10 per group; mean ± SD: age = 24 ± 3 yr) trained three times per week for 6 wk with SIT, 30-s all-out run sprints (manually driven treadmill), four to six bouts per session, 4-min recovery per bout, versus ET, 65% VO(2max) for 30 to 60 min·d(-1). RESULTS Training improved (P < 0.05) body composition, 2000-m run time trial performance, and VO(2max) in both groups. Fat mass decreased 12.4% with SIT (mean ± SEM; 13.7 ± 1.6 to 12.0 ± 1.6 kg) and 5.8% with ET (13.9 ± 1.7 to 13.1 ± 1.6 kg). Lean mass increased 1% in both groups. Time trial performance improved 4.6% with SIT (-25.6 ± 8.1 s) and 5.9% with ET (-31.9 ± 6.3 s). VO(2max) increased 11.5% with SIT (46.8 ± 1.6 to 52.2 ± 2.0 mL·kg·(-1)·min(-1)) and 12.5% with ET (44.0 ± 2.0 to 49.5 ± 2.6 mL·kg·(-1)·min(-1)). None of these improvements differed between groups. In contrast, Q(max) increased by 9.5% with ET only (22.2 ± 2.0 to 24.3 ± 1.6 L·min(-1)). CONCLUSIONS Despite a fraction of the time commitment, run SIT induces similar body composition, VO(2max), and performance adaptations as ET, but with no effect on Q(max). These data suggest that adaptations with ET are of central origin primarily, whereas those with SIT are more peripheral

Beyond the Zone: Protein Needs of Active Individuals

There has been debate among athletes and nutritionists regarding dietary protein needs for centuries. Although contrary to traditional belief, recent scientific information collected on physically active individuals tends to indicate that regular exercise increases daily protein requirements; however, the precise details remain to be worked out. Based on laboratory measures, daily protein requirements are increased by perhaps as much as 100% vs. recommendations for sedentary individuals (1.6–1.8 vs. 0.8 g/kg). Yet even these intakes are much less than those reported by most athletes. This may mean that actual requirements are below what is needed to optimize athletic performance, and so the debate continues. Numerous interacting factors including energy intake, carbohydrate availability, exercise intensity, duration and type, dietary protein quality, training history, gender, age, timing of nutrient intake and the like make this topic extremely complex. Many questions remain to be resolved. At the present time, substantial data indicate that the current recommended protein intake should be adjusted upward for those who are physically active, especially in populations whose needs are elevated for other reasons, e.g., growing individuals, dieters, vegetarians, individuals with muscle disease-induced weakness and the elderly. For these latter groups, specific supplementation may be appropriate, but for most North Americans who consume a varied diet, including complete protein foods (meat, eggs, fish and dairy products), and sufficient energy the increased protein needs induced by a regular exercise program can be met in one’s diet.

Effect of exercise on protein requirements

The effect(s) of exercise on dietary protein requirements has (have) been a controversial topic for many years. Although most expert committees on nutrition have not provided an additional allowance of protein for active individuals, a considerable amount of experimental evidence has accumulated during the past 15 years which indicates that regular exercise does in fact increase protein needs. Part of the confusion is due to methodological difficulties and inadequate control of several interacting factors including: diet composition, total energy intake, exercise intensity, duration and training, ambient temperature, gender, and perhaps even age. Although definitive dietary recommendations for various athletic groups must await future study, the weight of current evidence suggests that strength or speed athletes should consume about 1.2-1.7 g protein/kg body weight.d-1 (approximately 100-212% of current recommendations) and endurance athletes about 1.2-1.4 g/kg.d-1 (approximately 100-175% of current recommendations). These quantities of protein can be obtained from a diet which consists of 12-15% energy from protein, unless total energy intake is insufficient. There is no evidence that protein intakes in this range will cause any adverse effects. Future studies with large sample sizes, adequate controls, and performance as well as physiological/biochemical measures are necessary to fine tune these recommendations.

Effect of creatine loading on anaerobic performance and skeletal muscle volume in NCAA Division I athletes.

OBJECTIVE We measured the effect of 3 d of creatine (Cr) supplementation on repeated sprint performance and thigh muscle volume in elite power athletes. METHODS Ten male (mean +/- standard deviation of body mass and percentage of fat (81.1 +/- 10.5 kg and 9.8 +/- 3.5) and ten female (58.4 +/- 5.3 kg and 15.0 +/- 3.4) athletes were matched for sex and 10-s cycle sprint scores, paired by rank, and randomly assigned to the Cr or placebo (P) group. Subjects completed six maximal 10-s cycle sprints interspersed with 60 s of recovery before and after 3 d of Cr (0.35 g/kg of fat-free mass) or P (maltodextrin) ingestion. Before and after supplementation, 10 contiguous transaxial images of both thighs were obtained with magnetic resonance imaging. RESULTS Cr supplementation resulted in statistically significant increases in body mass (0.9 +/- 0.1 kg, P < 0.03), total work during the first sprint (P < 0.04), and peak power during sprints 2 to 6 (P < 0.10). As expected, total work and peak power values for males were greater than those for their female counterparts during the initial sprint (P < 0.02); however, the reverse was true during the last three sprints (P < 0.01). Imaging data showed a 6.6% increase in thigh volume in five of six Cr subjects (P = 0.05). CONCLUSION These data indicate that 3 d of Cr supplementation can increase thigh muscle volume and may enhance cycle sprint performance in elite power athletes; moreover, this effect is greater in females as sprints are repeated.

Recovery from a cycling time trial is enhanced with carbohydrate-protein supplementation vs. isoenergetic carbohydrate supplementation

BackgroundIn this study we assessed whether a liquid carbohydrate-protein (C+P) supplement (0.8 g/kg C; 0.4 g/kg P) ingested early during recovery from a cycling time trial could enhance a subsequent 60 min effort on the same day vs. an isoenergetic liquid carbohydrate (CHO) supplement (1.2 g/kg).MethodsTwo hours after a standardized breakfast, 15 trained male cyclists completed a time trial in which they cycled as far as they could in 60 min (AMex) using a Computrainer indoor trainer. Following AMex, subjects ingested either C+P, or CHO at 10, 60 and 120 min, followed by a standardized meal at 4 h post exercise. At 6 h post AMex subjects repeated the time trial (PMex).ResultsThere was a significant reduction in performance for both groups in PMex versus AMex. However, performance and power decreases between PMex and AMex were significantly greater (p ≤ 0.05) with CHO (-1.05 ± 0.44 km and -16.50 ± 6.74 W) vs C+P (-0.30 ± 0.50 km and -3.86 ± 6.47 W). Fat oxidation estimated from RER values was significantly greater (p ≤ 0.05) in the C+P vs CHO during the PMex, despite a higher average workload in the C+P group.ConclusionUnder these experimental conditions, liquid C+P ingestion immediately after exercise increases fat oxidation, increases recovery, and improves subsequent same day, 60 min efforts relative to isoenergetic CHO ingestion.

Dietary protein requirements in athletes

Abstract Current dietary protein requirements were determined using essentially sedentary individuals and, therefore, are designed for the general population. Unfortunately, the recommendations from these studies have been applied to athletes as well. Because of the vast differences in daily energy expenditure alone this would seem to be a naive approach. Moreover in recent years, considerable evidence has accumulated on athletes, primarily those involved at each end of the exercise intensity-duration continuum, i.e., strength (weight lifting) to endurance (running, cycling, or swimming), suggesting that dietary protein needs may be greater by as much as 125% in comparison to sedentary individuals. The additional protein may be necessary for use as an auxiliary fuel for endurance exercise and as a supplementary source of amino acids to build and/or maintain the large muscle mass present in those who strength train. In addition, although more speculative, it is possible that other constituents in high quality protein sources, i.e., creatine, conjugated linoleic acid, carnosine, etc. may also be beneficial. Definitive dietary recommendations for various athletic populations must await further study, but the mass of current evidence indicates that individuals involved in strength/power/speed activities may benefit from intakes of about 1.7 to 1.8 g protein · g body mass −1 · day −1 (approximately 112–125% higher than the sedentary recommendation) and those who participate in endurance activities from about 1.2–1.4 g · kg −1 · d −1 (approximately 50 to 75% higher than the sedentary recommendation). Assuming total energy intake is sufficient to cover expenditure, these intakes can be obtained from a diet consisting of about 10% energy intake as protein. Some athletes may not consume this amount of protein, especially those who consume inadequate energy (dieters or those trying to maintain an arbitrary body mass for their activity, i.e., gymnasts, dancers, wrestlers, etc.), those who are growing (children, adolescents, women who are pregnant), or those who select diets which may exclude high quality protein sources (vegetarians and seniors). Despite the common practice of consuming greater amounts of protein (2–4 g · kg −1 · d −1 ) among strength athletes in particular, few data exist suggesting that this has any further benefit, i.e., there appears to be a ceiling effect. Finally, the concerns expressed routinely about liver or kidney problems with high protein diets have little scientific support; however, the easy accessibility of individual amino acid supplements poses a potentially serious threat because there are likely a variety of confounding interactions and the effects of mega doses of single amino acids are largely untested. Future studies are needed to fine tune these recommendations.

Menstrual cycle and exercise effects on protein catabolism.

The purpose of this investigation was to determine whether exercise at different times of the menstrual cycle alters protein catabolism. Nine women exercised for 60 min at 70% VO2max when serum estradiol (E) and progesterone (P) were low (menses) and when both were high [mid-luteal (ML)]. Diet was reproduced on both occasions. Serum urea nitrogen (N), E, and P were analyzed at rest, after 15, 30, 45, and 60 min of exercise, and 15 min into recovery. Sweat urea N excretion was also determined. Urinary area N excretion was measured the day before, the day of, and 2 d following exercise. E and P were significantly greater in the ML phase, and this difference was maintained throughout exercise (P less than 0.05). No change was seen in serum urea N across exercise or between phases. Both exercise day urinary urea N excretion and total urea N excretion in sweat and urine, when added across all experimental days, were significantly greater in the ML phase compared to menses (8.5 +/- 0.96 vs 5.5 +/- 0.81 g and 24.8 +/- 2.38 vs 19.3 +/- 1.38 g, respectively, P less than 0.05). The data suggest that the greater protein use in the ML phase was due to the combined effects of exercise, a changing hormonal milieu and other unknown causes.

Protein intake and athletic performance.

SummaryFor most of the current century, exercise/nutritional scientists have generally accepted the belief that exercise has little effect on protein/amino acid requirements. However, during the same time period many athletes (especially strength athletes) have routinely consumed diets high in protein. In recent years, the results of a number of investigations involving both strength and endurance athletes indicate that, in fact, exercise does increase protein/amino acid need. For endurance athletes, regular exercise may increase protein need by 50 to 100%. For strength athletes, the data are less clear; however, protein intakes in excess of sedentary needs may enhance muscle development. Despite these observations increased protein intake may not improve athletic performance because many athletes routinely consume 150 to 200% of sedentary protein requirements. Assuming total energy intake is sufficient to cover the high expenditures caused by daily training, a diet containing 12 to 15% of its energy from protein should be adequate for both types of athletes.

Protein and exercise: update 1987

Currently, the recommended dietary allowance for protein determined for sedentary individuals is assumed to be adequate for athletes. However, several types of evidence (in vitro, in situ, and in vivo) indicate that exercise causes substantial changes in protein metabolism. In fact, recent data suggest the protein recommended dietary allowance may actually be 50 to 100% higher for individuals who exercise on a regular basis. Optimal intakes, although unknown, may even be higher, especially for individuals attempting to increase muscle mass and strength. The reasons why the recent experimental results contradict older studies are complex and not fully understood. However, dietary (total energy input, percent of each foodstuff, accommodation to treatments), exercise (type, frequency, intensity, duration, training, environment), and methodological (in vitro, in situ, in vivo) considerations are likely very important. This paper reviews the recent findings and discusses their implications to exercise performance. Although, definitive recommendations regarding optimal protein intakes for various athletic groups are not yet possible, it appears that exercise increases protein needs. It is hoped that well-controlled studies will be completed in the near future so that such recommendations will soon be possible.

The Importance of Protein for Athletes

SummaryAlthough it is generally believed that carbohydrate and fat are the only sources of energy during physical activity, recent experimental results suggest that there are also significant alterations in protein metabolism during exercise. Depending on several factors, including intensity, duration and type of exercise, as well as prior diet, training, environment and perhaps even gender or age, these changes may be quite large.Generally, exercise promotes: (a) a decrease in protein synthesis (production) unless the exercise duration is prolonged (> 4h) when increases occur; (b) either an increase or no change in protein catabolism (breakdown); and (c) an increase in amino acid oxidation. In addition, significant subcellular damage to skeletal muscle has been shown following exercise. Taken together, these observations suggest that the protein requirements of active individuals are greater than those of inactive individuals. Although the underlying reasons are different, this statement applies to both endurance and strength/power athletes.At present, it is not possible to precisely determine protein requirements. However, because deficiencies in total protein or in specific amino acids may occur, we suggest that athletes consume 1.8 to 2.0g of protein/kg of body weight/day. This is approximately twice the recommended requirement for sedentary individuals. For some athletes this may require supplementation; however, these quantities of protein can be easily obtained in a diet where 12 to 15% of the total energy is from protein.Although the effect of exercise on protein metabolism has been studied for many years, numerous questions remain. Hopefully, with the recent renewed interest in this area of study, most of these answers will soon be available.