Patterns of energy availability of free-living athletes display day-to-day variability that is not reflected in laboratory-based protocols: Insights from elite male road cyclists.

The physiological effects of low energy availability (EA) have been studied using a homogenous daily EA pattern in laboratory settings. However, whether this daily EA pattern represents those of free-living athletes and is therefore ecologically valid is unknown. To investigate this, we assessed daily exercise energy expenditure, energy intake and EA in 10 free-living elite male road cyclists (20 min Mean Maximal Power: 5.27 ± 0.25 W · kg-1) during 7 consecutive days of late pre-season training. Energy intake was measured using the remote-food photography method and exercise energy expenditure estimated from cycling crank-based power-metres. Seven-day mean ± SD energy intake and exercise energy expenditure was 57.9 ± 10.4 and 38.4 ± 8.6 kcal · kg FFM-1 · day-1, respectively. EA was 19.5 ± 9.1 kcal · kg FFM-1 · day-1. Within-participants correlation between daily energy intake and exercise energy expenditure was .62 (95% CI: .43 - .75; P < .001), and .60 (95% CI: .41 - .74; P < .001) between carbohydrate intake and exercise energy expenditure. However, energy intake only partially compensated for exercise energy expenditure, increasing 210 kcal · day-1 per 1000 kcal · day-1 increase in expenditure. EA patterns displayed marked day-to-day fluctuation (range: -22 to 76 kcal · kg FFM-1 · day-1). The validity of research using homogenous low EA patterns therefore requires further investigation.

Low energy availability: history, definition and evidence of its endocrine, metabolic and physiological effects in prospective studies in females and males.

Energy availability (EA) is defined as the amount of dietary energy available to sustain physiological function after subtracting the energetic cost of exercise. Insufficient EA due to increased exercise, reduced energy intake, or a combination of both, is a potent disruptor of the endocrine milieu. As such, EA is conceived as a key etiological factor underlying a plethora of physiological dysregulations described in the female athlete triad, its male counterpart and the Relative Energy Deficiency in Sport models. Originally developed upon female-specific physiological responses, this concept has recently been extended to males, where experimental evidence is limited. The majority of data for all these models are from cross-sectional or observational studies where hypothesized chronic low energy availability (LEA) is linked to physiological maladaptation. However, the body of evidence determining causal effects of LEA on endocrine, and physiological function through prospective studies manipulating EA is comparatively small, with interventions typically lasting ≤ 5 days. Extending laboratory-based findings to the field requires recognition of the strengths and limitations of current knowledge. To aid this, this review will: (1) provide a brief historical overview of the origin of the concept in mammalian ecology through its evolution of algebraic calculations used in humans today, (2) Outline key differences from the 'energy balance' concept, (3) summarise and critically evaluate the effects of LEA on tissues/systems for which we now have evidence, namely: hormonal milieu, reproductive system endocrinology, bone metabolism and skeletal muscle; and finally (4) provide perspectives and suggestions for research upon identified knowledge gaps.

Post-Exercise Carbohydrate-Energy Replacement Attenuates Insulin Sensitivity and Glucose Tolerance the Following Morning in Healthy Adults.

The carbohydrate deficit induced by exercise is thought to play a key role in increased post-exercise insulin action. However, the effects of replacing carbohydrate utilized during exercise on postprandial glycaemia and insulin sensitivity are yet to be determined. This study therefore isolated the extent to which the insulin-sensitizing effects of exercise are dependent on the carbohydrate deficit induced by exercise, relative to other exercise-mediated mechanisms. Fourteen healthy adults performed a 90-min run at 70% V ˙ O 2 max starting at 1600-1700 h before ingesting either a non-caloric artificially-sweetened placebo solution (CHO-DEFICIT) or a 15% carbohydrate solution (CHO-REPLACE; 221.4 ± 59.3 g maltodextrin) to precisely replace the measured quantity of carbohydrate oxidized during exercise. The alternate treatment was then applied one week later in a randomized, placebo-controlled, and double-blinded crossover design. A standardized low-carbohydrate evening meal was consumed in both trials before overnight recovery ahead of a two-hour oral glucose tolerance test (OGTT) the following morning to assess glycemic and insulinemic responses to feeding. Compared to the CHO-DEFICIT condition, CHO-REPLACE increased the incremental area under the plasma glucose curve by a mean difference of 68 mmol·L-1 (95% CI: 4 to 132 mmol·L-1; p = 0.040) and decreased the Matsuda insulin sensitivity index by a mean difference of -2 au (95% CI: -1 to -3 au; p = 0.001). This is the first study to demonstrate that post-exercise feeding to replaceme the carbohydrate expended during exercise can attenuate glucose tolerance and insulin sensitivity the following morning. The mechanism through which exercise improves insulin sensitivity is therefore (at least in part) dependent on carbohydrate availability and so the day-to-day metabolic health benefits of exercise might be best attained by maintaining a carbohydrate deficit overnight.

Automated collection of double red blood cell units with a variable-volume separation chamber.

BACKGROUND: Automated collection of blood components offers multiple advantages and has prompted development of portable devices. This study sought to document the biochemical and hematologic properties and in vivo recovery of red cells (RBCs) collected via a new device that employed a variable-volume centrifugal separation chamber. STUDY DESIGN AND METHODS: Normal subjects (n = 153) donated 2 units of RBCs via an automated blood collection system (Cymbal, Haemonetics). Procedures were conducted with wall outlet power (n = 49) or the device's battery source (n = 104). Units were collected with or without leukoreduction filtration and were stored in AS-3 for 42 days. The units were assessed via standard biochemical and hematologic tests before and after storage, and 24 leukoreduced (LR) and 24 non-LR RBCs were radiolabeled on Day 42 with Na(2)(51)CrO(4) for autologous return to determine recovery at 24 hours with concomitant determination of RBC volume via infusion of (99m)Tc-labeled fresh RBCs. RESULTS: Two standard RBC units (targeted to contain 180 mL of RBCs plus 100 mL of AS-3) could be collected in 35.7 +/- 2.0 minutes (n = 30) or 40.3 +/- 2.7 minutes for LR RBCs (n = 92). An additional 31 collections were conducted successfully with intentional filter bypassing. RBC units contained 104 +/- 4.1 percent of their targeted volumes (170-204 mL of RBCs), and LR RBCs contained 92 percent of non-LR RBCs' hemoglobin. All LR RBCs contained less than 1 x 10(6) white blood cells. Mean hemolysis was below 0.8 percent (Day 42) for all configurations. Adenosine triphosphate was well preserved. Mean recovery was 82 +/- 4.9 percent for RBCs and 84 +/- 7.0 percent for LR RBCs. CONCLUSIONS: The Cymbal device provided quick and efficient collection of 2 RBC units with properties meeting regulatory requirements and consistent with good clinical utility.

Extended storage of AS-1 and AS-3 leukoreduced red blood cells for 15 days after deglycerolization and resuspension in AS-3 using an automated closed system.

BACKGROUND: The utilization of cryopreserved red blood cell (RBC) units had been limited by a maximum postdeglycerolization storage of 24 hours at 1 to 6 degrees C until the recent development of a closed system for the glycerolization and deglycerolization process. STUDY DESIGN AND METHODS: Sixty leukoreduced additive solution (AS), AS-1 (n = 30) and AS-3 (n = 30) RBC units from 500-mL whole blood (WB) collections were stored for 6 days, glycerolized, frozen at -70 +/- 5 degrees C for at least 14 days, thawed, deglycerolized, and stored for 15 days at 1 to 6 degrees C. Glycerolization and deglycerolization were performed with the ACP 215. In-vitro variables were tested before glycerolization, on Day 0, and Day 15 after deglycerolization storage. Forty donors were assessed for double-label 24-hour percent recovery, and T1/2 survival time was measured for 20 donors. RESULTS: Postdeglycerolization mean +/- standard deviation in-vitro RBC mass recoveries were 93 +/- 5 percent for AS-1 and 95 +/- 4 percent for AS-3. Mean hemoglobin +/- standard deviation after deglycerolization was 50.5 +/- 5.5g for AS-1 and 50.1 +/- 3.5g for AS-3. Mean hemolysis (Day 15) was 0.36 +/- 0.11 percent for AS-1 and 0.38 +/- 0.13 percent for AS-3. Double-label 24-hour in-vivo recoveries were 82.5 +/- 7.8 percent for AS-1 and 81.4 +/- 7.1 percent for AS-3. The 51Cr T1/2 value was 41.8 +/- 3.97 for AS-1 and 40.6 +/- 7.11 for AS-3. Other in-vitro variables were as expected. CONCLUSION: Leukoreduced AS-1 and AS-3 RBCs after frozen storage at -70 +/- 5 degrees C can be stored for up to 14 days when processing is performed with the ACP 215 system with resuspension of deglycerolized RBCs in AS-3.