Creatine Supplementation in Women's Health: A Lifespan Perspective.

Despite extensive research on creatine, evidence for use among females is understudied. Creatine characteristics vary between males and females, with females exhibiting 70-80% lower endogenous creatine stores compared to males. Understanding creatine metabolism pre- and post-menopause yields important implications for creatine supplementation for performance and health among females. Due to the hormone-related changes to creatine kinetics and phosphocreatine resynthesis, supplementation may be particularly important during menses, pregnancy, post-partum, during and post-menopause. Creatine supplementation among pre-menopausal females appears to be effective for improving strength and exercise performance. Post-menopausal females may also experience benefits in skeletal muscle size and function when consuming high doses of creatine (0.3 g·kg-1·d-1); and favorable effects on bone when combined with resistance training. Pre-clinical and clinical evidence indicates positive effects from creatine supplementation on mood and cognition, possibly by restoring brain energy levels and homeostasis. Creatine supplementation may be even more effective for females by supporting a pro-energetic environment in the brain. The purpose of this review was to highlight the use of creatine in females across the lifespan with particular emphasis on performance, body composition, mood, and dosing strategies.

The Role of Creatine in the Development and Activation of Immune Responses.

The use of dietary supplements has become increasingly common over the past 20 years. Whereas supplements were formerly used mainly by elite athletes, age and fitness status no longer dictates who uses these substances. Indeed, many nutritional supplements are recommended by health care professionals to their patients. Creatine (CR) is a widely used dietary supplement that has been well-studied for its effects on performance and health. CR also aids in recovery from strenuous bouts of exercise by reducing inflammation. Although CR is considered to be very safe in recommended doses, a caveat is that a preponderance of the studies have focused upon young athletic individuals; thus there is limited knowledge regarding the effects of CR on children or the elderly. In this review, we examine the potential of CR to impact the host outside of the musculoskeletal system, specifically, the immune system, and discuss the available data demonstrating that CR can impact both innate and adaptive immune responses, together with how the effects on the immune system might be exploited to enhance human health.

Resistance Training during Chemotherapy with Doxorubicin.

Previous research has shown that resistance training (RT) before doxorubicin (DOX) treatment attenuates the decline in muscle dysfunction; however, the effect of RT during DOX treatment is less known. PURPOSE: Investigate the effects of RT before and during a 4-wk course of incremental DOX treatment on skeletal muscle function. METHODS: Male, Sprague-Dawley rats (N = 36) were randomly assigned to the following groups: sedentary+saline (SED + SAL), sedentary+DOX (SED + DOX), RT + SAL, or RT + DOX. The RT protocol utilized a raised cage model, which provided progressive hindlimb loading throughout the 14-wk study, whereas SED animals were kept in normal housing. Starting at week 10, DOX-treated animals received 3 mg·kg DOX weekly for 4 wk (12 mg·kg cumulative); whereas SAL-treated groups received 0.9% NaCl as a placebo. Grip strength was recorded at 0, 10, 12, and 14 wk. Ex vivo muscle function was performed on excised soleus (SOL) and extensor digitorum longus (EDL) from the right hind limb 5 d after the last injection and were analyzed for expression of creatine kinase (CK) and creatine transporters. RESULTS: SED + DOX-treated animals had significantly lower EDL mass compared with SED + SAL- and RT + DOX-treated animals. Grip strength, EDL maximal force, and EDL force development were significantly lower in SED + DOX-treated animals compared with RT + SAL and SED + SAL. No significant differences in EDL function were found between RT + DOX and RT + SAL animals. DOX treatment reduced expression of CK in the SOL, which abated with RT. CONCLUSIONS: Low-intensity RT may attenuate the decline in skeletal muscle function during incremental DOX treatment.

Beyond muscles: The untapped potential of creatine.

Creatine is widely used by both elite and recreational athletes as an ergogenic aid to enhance anaerobic exercise performance. Older individuals also use creatine to prevent sarcopenia and, accordingly, may have therapeutic benefits for muscle wasting diseases. Although the effect of creatine on the musculoskeletal system has been extensively studied, less attention has been paid to its potential effects on other physiological systems. Because there is a significant pool of creatine in the brain, the utility of creatine supplementation has been examined in vitro as well as in vivo in both animal models of neurological disorders and in humans. While the data are preliminary, there is evidence to suggest that individuals with certain neurological conditions may benefit from exogenous creatine supplementation if treatment protocols can be optimized. A small number of studies that have examined the impact of creatine on the immune system have shown an alteration in soluble mediator production and the expression of molecules involved in recognizing infections, specifically toll-like receptors. Future investigations evaluating the total impact of creatine supplementation are required to better understand the benefits and risks of creatine use, particularly since there is increasing evidence that creatine may have a regulatory impact on the immune system.

Acute ingestion of sugar-free red bull energy drink has no effect on upper body strength and muscular endurance in resistance trained men.

Consumption of energy drinks by both recreational and competitive athletes has increased dramatically in recent years. The primary ingredients in many energy drinks include caffeine (CAF) in various forms and taurine. The purpose of this randomized, double-blind, crossover study was to examine the effect of sugar-free (SF) Red Bull (RB) containing CAF and taurine to a CAF only drink and a SF CAF-free placebo (PL) on 1 repetition maximum (1RM) bench press (BP) and the volume load (VL; repetitions × kg at 70% 1RM) during one BP set to failure in experienced lifters. Seventeen college-age men randomly received the following: (A) 500 mL of SF-RB containing CAF (160 mg) and taurine (2000 mg); (B) 500 mL of a SF drink containing CAF only (160 mg); or (C) a SF CAF-free 500 mL PL drink 60 minutes before testing on 3 separate occasions. After a standard warm-up, the 1RM was determined for each subject and, after 5 minutes rest, they completed repetitions to failure at 70% of their 1RM to assess VL. Differences between trials for 1RM BP and the VL were identified using repeated measures analysis of variance (p < 0.05). The results indicated that neither SF-RB nor the CAF drink had any effect on 1RM BP (115.13 ± 16.19 kg and 114.87 ± 16.16 kg, respectively) or VL (1173.08 ± 170.66 kg and 1164.14 ± 147.03 kg, respectively) compared with PL (1RM = 114.07 ± 16.09 kg; VL = 1141.46 ± 193.41 kg). Although the CAF content in the energy drinks used in the present study was low (∼2.0 mg/kg), the finding of no effect of the CAF containing energy drinks for 1RM BP are in agreement with previous studies using intakes up to 6.0 mg/kg. These findings suggest that SF-RB has no effect on upper body 1RM strength or VL in resistance trained men.

Reliability of three measures of ankle dorsiflexion range of motion.

PURPOSE/BACKGROUND: A variety of methods exist to measure ankle dorsiflexion range of motion (ROM). Few studies have examined the reliability of a novice rater. The purpose of this study was to determine the reliability of ankle ROM measurements using three different techniques in a novice rater. METHODS: Twenty healthy subjects (mean±SD, age=24±3 years, height=173.2±8.1 cm, mass=72.6±15.2 kg) participated in this study. Ankle dorsiflexion ROM measures were obtained in a weight-bearing lunge position using a standard goniometer, digital inclinometer, and a tape measure using the distance-to-wall technique. All measures were obtained three times per side, with 10 minutes of rest between the first and second set of measures. Intrarater reliability was determined using an intraclass correlation coefficient (ICC(2,3)) and associated 95% confidence intervals (CI). Standard error of measurement (SEM) and the minimal detectable change (MDC) for each measurement technique were also calculated. RESULTS: The within-session intrarater reliability (ICC(2,3)) estimates for each measure are as follows: tape measure (right 0.98, left 0.99), digital inclinometer (right 0.96; left 0.97), and goniometer (right 0.85; left 0.96). The SEM for the tape measure method ranged from 0.4-0.6 cm and the MDC was between 1.1-1.5 cm. The SEM for the inclinometer was between 1.3-1.4° and the MDC was 3.7-3.8°. The SEM for the goniometer ranged from 1.8-2.8° with an MDC of 5.0-7.7°. CONCLUSIONS: The results indicate that reliable measures of weight-bearing ankle dorsiflexion ROM can be obtained from a novice rater. All three techniques had good reliability and low measurement error, with the distance-to-wall technique using a tape measure and inclinometer methods resulting in higher reliability coefficients (ICC(2,3)=0.96 to 0.99) and a lower SEM compared to the goniometer (ICC(2,3)=0.85 to 0.96). LEVEL OF EVIDENCE: 2b.

Estimating body fat in NCAA Division I female athletes: a five-compartment model validation of laboratory methods.

The purpose of the present study was to determine the validity of various laboratory methods for estimating percent body fat (%fat) in NCAA Division I college female athletes (n = 29; 20 +/- 1 year). Body composition was assessed via hydrostatic weighing (HW), air displacement plethysmography (ADP), and dual-energy X-ray absorptiometry (DXA), and estimates of %fat derived using 4-compartment (C), 3C, and 2C models were compared to a criterion 5C model that included bone mineral content, body volume (BV), total body water, and soft tissue mineral. The Wang-4C and the Siri-3C models produced nearly identical values compared to the 5C model (r > 0.99, total error (TE) < 0.40%fat). For the remaining laboratory methods, constant error values (CE) ranged from -0.04%fat (HW-Siri) to -3.71%fat (DXA); r values ranged from 0.89 (ADP-Siri, ADP-Brozek) to 0.93 (DXA); standard error of estimate values ranged from 1.78%fat (DXA) to 2.19%fat (ADP-Siri, ADP-Brozek); and TE values ranged from 2.22%fat (HW-Brozek) to 4.90%fat (DXA). The limits of agreement for DXA (-10.10 to 2.68%fat) were the largest with a significant trend of -0.43 (P < 0.05). With the exception of DXA, all of the equations resulted in acceptable TE values (<3.08%fat). However, the results for individual estimates of %fat using the Brozek equation indicated that the 2C models that derived BV from ADP and HW overestimated (5.38, 3.65%) and underestimated (5.19, 4.88%) %fat, respectively. The acceptable TE values for both HW and ADP suggest that these methods are valid for estimating %fat in college female athletes; however, the Wang-4C and Siri-3C models should be used to identify individual estimates of %fat in this population.

Effect of thirty days of creatine supplementation with phosphate salts on anaerobic working capacity and body weight in men.

The purpose of this study was to determine the effect of 30 days of single-dose creatine supplementation with phosphate salts (CPS) on body weight (BW) and anaerobic working capacity (AWC) in men. Using a double-blind design, 32 men randomly received 1 serving of either CPS (5 g Cr + 4 g phosphate) (n = 17) or 20 g of dextrose as placebo (PL) (n = 15) for 30 days. AWC determined from the Critical Power Test and BW were measured at baseline, 10 days, 20 days, 30 days, and 10 days post-supplementation. Results (2 x 5 ANOVA) showed no significant differences between groups for AWC at any time point; however, BW was significantly increased at 10 days in the CPS group (1.0 kg) vs. PL (0.0 kg), and remained elevated for the duration of the study. These findings suggest that a single 5 g x d(-1) dose of CPS for 30 days increases BW but is not effective for increasing AWC in men.

Effect of creatine phosphate supplementation on anaerobic working capacity and body weight after two and six days of loading in men and women.

The purpose of this study was to determine the effects of 2 and 6 days of creatine phosphate loading on anaerobic working capacity (AWC) and body weight (BW) in men and women. Sixty-one men (n = 31) and women (n = 30) randomly received 1 of 3 treatments (4 x 5 g.d(-1) x 6 days) using a double blind design: (a) 18 g dextrose as placebo (PL); (b) 5.0 g Cr + 20 g dextrose (Cr); or (c) 5.0 g Cr + 18 g dextrose + 4 g of sodium and potassium phosphates (CrP). AWC was determined at baseline and following 2 and 6 days of supplementation using the Critical Power Test. BW increased significantly over time, and the mean value for the men was significantly greater compared to that for women, but there were no interactions (p > 0.05). There were gender-specific responses for AWC expressed in both absolute values (kJ) and relative to BW (kJ. kg(-1)), with the women demonstrating no significant interactions. For the men, CrP loading significantly increased AWC following 2 days (23.8%) and 6 days (49.8%) of supplementation vs. PL (kJ and kJ.kg(-1)). Cr supplementation increased AWC 13-15% in both genders compared to PL (1.1%- 3.0% decline); although this result was not statistically significant, it may have some practical significance.

Accuracy of near-infrared interactance instruments and population-specific equations for estimating body composition in young wrestlers.

The purpose of this investigation was to determine the accuracy of near-infrared interactance (NIR) instruments and population-specific NIR equations for estimating percent body fat (% fat) in young wrestlers. Forty-four white male youth wrestlers (mean age +/- SD = 11.0 +/- 2.1 years) volunteered for this study. Thirteen NIR % fat estimates were cross-validated against the criterion % fat from underwater weighing. The results of this study indicated that the total error (TE) values associated with the NIR instrument generated % fat estimates as well as % fat estimates from population-specific NIR equations developed for high school wrestlers or adult men were too large (TE = 5.7-27.3% fat) to be used with young wrestlers. Based on the present findings, it is recommended that new NIR equations be developed and validated specifically for use in young male athletes.

Effect of two and five days of creatine loading on anaerobic working capacity in women.

The purpose of this study was to determine the effects of 2 and 5 days of Cr loading on anaerobic working capacity (AWC) using the critical power (CP) test in women. Ten physically active women randomly received 2 treatments separated by a 5 week washout period: (A) 18 g dextrose as placebo (PL) or (B) 5.0 g Cr + 18 g dextrose taken 4 times per day for 5 days. Following a familiarization trial, each subject completed the CP test at baseline and following 2 and 5 days of supplementation. The PL resulted in no significant changes in AWC following supplementation; however, Cr increased AWC by 22.1% after 5 days of loading (p < 0.05). There was a significant main effect for body weight (BW), however, there was no significant increase in BW due to Cr supplementation. These results suggest that Cr supplementation is effective for increasing AWC in women following 5 days of loading without an associated increase in BW.