The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis an...

http://www.afboard.com/library/creatinemetabolism.pdf

Creatine and Creatinine Metabolism

Despite extensive use over 40 years, physical activity questionnaires still show limited reliability and validity. Measurements have value in indicating conditions where an increase in physical activity would be beneficial and in monitoring changes in population activity. However, attempts at detailed interpretation in terms of exercise dosage and the extent of resulting health benefits seem premature. Such usage may become possible through the development of standardised instruments that will record the low intensity activities typical of sedentary societies, and will ascribe consistent biological meaning to terms such as light, moderate, and heavy exercise.

https://bjsm.bmj.com/content/bjsports/37/3/197.full.pdf

Limits to the measurement of habitual physical activity by questionnaires

The literature related to Borg's ratings of perceived exertion (RPE) scale has revealed inconsistencies about the strength of the relationship between ratings of perceived exertion and various physiological criterion measures, such as heart rate, blood lactate concentration, percent maximal oxygen uptake (% V O 2max ), oxygen uptake ( V O 2 ), ventilation and respiration rate. Using sex of participants, fitness, type of RPE scale used, type of exercise, exercise protocol, RPE mode and study quality, we undertook a meta-analysis to determine the strength of the relationship between RPE scores and the six aforementioned physiological measures. The weighted mean validity coefficients were 0.62 for heart rate, 0.57 for blood lactate, 0.64 for % V O 2max , 0.63 for V O 2 , 0.61 for ventilation and 0.72 for respiration rate. Analysis of moderator variables revealed that the following study features could account for the variation of results across studies: heart rate - fitness, type of exercise, protocol and RP...

Criterion-related validity of the Borg ratings of perceived exertion scale in healthy individuals: a meta-analysis.

Many coaches, athletes and sports medicine personnel hold the belief, based on observations and experiences, that massage can provide several benefits to the body such as increased blood flow, reduced muscle tension and neurological excitability, and an increased sense of well-being. Massage can produce mechanical pressure, which is expected to increase muscle compliance resulting in increased range of joint motion, decreased passive stiffness and decreased active stiffness (biomechanical mechanisms). Mechanical pressure might help to increase blood flow by increasing the arteriolar pressure, as well as increasing muscle temperature from rubbing. Depending on the massage technique, mechanical pressure on the muscle is expected to increase or decrease neural excitability as measured by the Hoffman reflex (neurological mechanisms). Changes in parasympathetic activity (as measured by heart rate, blood pressure and heart rate variability) and hormonal levels (as measured by cortisol levels) following massage result in a relaxation response (physiological mechanisms). A reduction in anxiety and an improvement in mood state also cause relaxation (psychological mechanisms) after massage. Therefore, these benefits of massage are expected to help athletes by enhancing performance and reducing injury risk. However, limited research has investigated the effects of pre-exercise massage on performance and injury prevention. Massage between events is widely investigated because it is believed that massage might help to enhance recovery and prepare athletes for the next event. Unfortunately, very little scientific data has supported this claim. The majority of research on psychological effects of massage has concluded that massage produces positive effects on recovery (psychological mechanisms). Post-exercise massage has been shown to reduce the severity of muscle soreness but massage has no effects on muscle functional loss. Notwithstanding the belief that massage has benefits for athletes, the effects of different types of massage (e.g. petrissage, effleurage, friction) or the appropriate timing of massage (pre-exercise vs post-exercise) on performance, recovery from injury, or as an injury prevention method are not clear. Explanations are lacking, as the mechanisms of each massage technique have not been widely investigated. Therefore, this article discusses the possible mechanisms of massage and provides a discussion of the limited evidence of massage on performance, recovery and muscle injury prevention. The limitations of previous research are described and further research is recommended.

http://yunus.hacettepe.edu.tr/~nazank/SBR330Masaj/The%20mechanisms%20of%20massage%20&%20effects%20on%20performance,%20muscle%20recovery,%20injury%20prevention.pdf

The Mechanisms of Massage and Effects on Performance, Muscle Recovery and Injury Prevention

Creatine (Cr) supplementation has become a common practice among professional, elite, collegiate, amateur, and recreational athletes with the expectation of enhancing exercise performance. Research indicates that Cr supplementation can increase muscle phosphocreatine (PCr) content, but not in all individuals. A high dose of 20 g x d(-1) that is common to many research studies is not necessary, as 3 g x d(-1) will achieve the same increase in PCr given time. Coincident ingestion of carbohydrate with Cr may increase muscle uptake; however, the procedure requires a large amount of carbohydrate. Exercise performance involving short periods of extremely powerful activity can be enhanced, especially during repeated bouts of activity. This is in keeping with the theoretical importance of an elevated PCr content in skeletal muscle. Cr supplementation does not increase maximal isometric strength, the rate of maximal force production, nor aerobic exercise performance. Most of the evidence has been obtained from healthy young adult male subjects with mixed athletic ability and training status. Less research information is available related to the alterations due to age and gender. Cr supplementation leads to weight gain within the first few days, likely due to water retention related to Cr uptake in the muscle. Cr supplementation is associated with an enhanced accrual of strength in strength-training programs, a response not independent from the initial weight gain, but may be related to a greater volume and intensity of training that can be achieved. There is no definitive evidence that Cr supplementation causes gastrointestinal, renal, and/or muscle cramping complications. The potential acute effects of high-dose Cr supplementation on body fluid balance has not been fully investigated, and ingestion of Cr before or during exercise is not recommended. There is evidence that medical use of Cr supplementation is warranted in certain patients (e.g.. neuromuscular disease); future research may establish its potential usefulness in other medical applications. Although Cr supplementation exhibits small but significant physiological and performance changes, the increases in performance are realized during very specific exercise conditions. This suggests that the apparent high expectations for performance enhancement, evident by the extensive use of Cr supplementation, are inordinate.

American College of Sports Medicine roundtable. The physiological and health effects of oral creatine supplementation.

The relationship between the ability to develop leg torque and performance in the vertical jump was investigated in 29 female athletes. Each subject's leg flexion, leg extension, and foot plantar flexion peak torque was determined isokinetically on a Cybex at angular velocities of 30 degrees/second and 180 degrees/second. The vertical jump was determined for each subject and correlations among the measures of torque and the vertical jump were calculated. Although the ability to produce leg power as exemplified by the vertical jump was significantly correlated with peak torque at the fast angular velocity but was not significantly correlated with peak torque at the slow angular velocity, the correlations were so low it was concluded that there was little if any relationship between torque at a fast or slow angular velocity and the ability to vertically jump.

The Relationship of Isokinetic Torque at Two Speeds to the Vertical Jump

We investigated the effect of creatine supplementation on maximal running performance in a simulated track competition. Twelve competitive male runners were assigned to either a placebo or creatine supplementation group. Both groups completed two maximal 700-m running bouts 60 min apart on an outdoor track. A second identical trial was performed 7 days later, and for 5 days prior to the second trial, subjects ingested 20 g.day-1 of either creatine monohydrate or a placebo. Subjects in the placebo group ran 110.2 +/- 3.5 s and 110.4 +/- 3.0 s for the first trial and 108.5 +/- 2.9 s and 108.0 +/- 1.7 s for the second trial, while the creatine group ran 109.9 +/- 3.2 s and 110.4 +/- 3.6 s for the first trial and 109.7 +/- 3.3 s and 107.8 +/- 2.2 s for the second trial. There were no significant differences between groups by trial or Trial X Time for running time, postexercise blood lactate concentration, or body weight (p > .05). We concluded that creatine supplementation does not enhance performance of single or twice-repeated maximal running bouts lasting 90-120 s.

The effect of creatine supplementation on two 700-m maximal running bouts.

The purposes of this study were (a) to validate the Rockport Fitness Walking Test (RFWT) in college students, and (b) to develop prediction equations on this college sample if the RFWT proved invalid. Subjects were administered a test to determine maximal oxygen uptake (VO2max) on a treadmill and the RFWT in afield testing environment. Comparisons were made between the measured VO2max and the VO2max predicted from the equations of Kline, Porcari, Hintermeister, et al. (1987). The Kline, Porcari, Hintermeister, et al. equations overpredicted VO2max by 16–18% in the males and by 22–23% in the females. The correlation coefficients between the measured and predicted VO2max values ranged from .39 to .59. Derivation of new prediction equations using the same variables as in the RFWT produced only one equation that had sufficient accuracy to recommend its use. It was concluded that the original RFWT overpredicts VO2max in college students and should not be used with this population.

Validation of the Rockport Fitness Walking Test in college males and females.

The purpose of this study was to determine the effects of carbohydrate refeeding on intermittent sprint exercise, blood lactate response, and mood following a typical weight-reduction program practiced by college wrestlers. Fifteen collegiate wrestlers from the University of Northern Iowa completed 3 trials of intermittent arm cranking and a mood inventory prior to weigh-ins (baseline), after weigh-ins, and 1 hour postconsumption of either 1.5 g carbohydrate (CHO)/kg body mass carbohydrate beverage (25% solution) or placebo taken within 1 hour after weigh-ins. Blood lactate responses were determined with each trial. Repeated measures analysis of variance indicated no significant interaction between group and trial for total work (p = 0.08), blood lactate (p = 0.29), positive mood (p = 0.49), or negative mood (p = 0.78). Simple effects analysis indicated a significant difference in lactate response between trials (p = 0.002); however, no difference for work (p = 0.75), positive mood (p = 0.13), or negative mood (p = 0.08). The results of this study suggest that intermittent sprint exercise, blood lactate response, and mood were not positively affected by ingestion of CHOs following an acute weight-reduction period.

Effects of carbohydrate refeeding on physiological responses and psychological and physical performance following acute weight reduction in collegiate wrestlers.

A series of body build and body composition variables were determined on a group of 29 female ballet and modern dancers. Comparisons were made between the dancers and other types of female athletes. The body build of the dancers was definitely different from that of nondancers. The dancers had lower body weights, lower LBW, smaller bideltoid, biacromial, bi-iliac, bi-trochanteric, and wrist diameters, and less body fat than the nondancers. Compared to other types of female athletes, the dancers had more body fat and less LBW. Somatograms of the dancers indicated that their body builds exhibited good symmetry.

Forrest A. Dolgener

Papers

The Relationship of Isokinetic Torque at Two Speeds to the Vertical Jump

The effect of creatine supplementation on two 700-m maximal running bouts.

Validation of the Rockport Fitness Walking Test in college males and females.

Effects of carbohydrate refeeding on physiological responses and psychological and physical performance following acute weight reduction in collegiate wrestlers.

Body Build and Body Composition of High Ability Female Dancers