ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients

Threshold for muscle lactate accumulation during progressive exercise

The purpose of this study was to investigate the relationship between muscle and blood lactate concentrations during progressive exercise. Seven endurance-trained male college students performed three incremental bicycle ergometer exercise tests. The first two tests (tests I and II) were identical and consisted of 3-min stage durations with 2-min rest intervals and increased by 50-W increments until exhaustion. During these tests, blood was sampled from a hyperemized earlobe for lactate and pH measurement (and from an antecubital vein during test I), and the exercise intensities corresponding to the lactate threshold (LT), individual anaerobic threshold (IAT), and onset of blood lactate accumulation (OBLA) were determined. The test III was performed at predetermined work loads (50 W below OBLA, at OBLA, and 50 W above OBLA), with the same stage and rest interval durations of tests I and II. Muscle biopsies for lactate and pH determination were taken at rest and immediately after the completion of the three exercise intensities. Blood samples were drawn simultaneously with each biopsy. Muscle lactate concentrations increased abruptly at exercise intensities greater than the “below-OBLA” stage [50.5% maximal O2 uptake (VO2 max)] and resembled a threshold. An increase in blood lactate and [H+] also occurred at the below-OBLA stage; however, no significant change in muscle [H+] was observed. Muscle lactate concentrations were highly correlated to blood lactate (r = 0.91), and muscle-to-blood lactate ratios at below-OBLA, at-OBLA, and above-OBLA stages were 0.74, 0.63, 0.96, and 0.95, respectively

Blood lactate threshold differences between arterialized and venous blood

The purpose of this study was to investigate the differences between lactate thresholds determined from venous and arterialized blood. Seven endurance-trained college males performed an incremental bicycle ergometer exercise test until exhaustion. At the end of each 3 min stage, blood was sampled simultaneously from a hyperemized ear-lobe and an antecubital vein for the measurement of blood lactate (La-). Two-minute rest intervals separated each stage. Arterialized blood La-concentrations ([La-]) were significantly higher than venous blood at 350 W (14.5 and 9.7 mmol·l-1), maximal exercise (15.5 and 11.39 mmol·l-1), and throughout recovery. Arterialized [La-] was significantly higher than venous blood at the onset of blood La- accumulation (OBLA) (4.0 and 2.8±0.1 mmol·l-1), the individual anaerobic threshold (IAT) (3.4+0.3 and 2.1±0.1 mmol·l-1), and the ventilatory threshold (VT) (4.7±0.9 and 3.2±0.6 mmol·l-1). No significant differences were found between either La-threshold for arterialized or venous blood. The oxygen consumption (V̇O2) at OBLA was significantly lower when determined from arterialized blood La (2.3±0.2 and 2.8±0.2 l·min-1). No significant differences existed between the LT, OBLA, and IAT threshold-V̇O2 determinations from arterialized blood; however, significant differences were found between IAT-OBLA (2.1±0.2 and 2.8±0.2 l·min-1) and LT (2.2±0.2 l·min-1)-OBLA from venous blood. These results indicate that differences between venous and arterialized blood [La-] need to be considered when comparing different anaerobic threshold determinations

Effects of warm-up on blood gases, lactate and acid-base status during sprint swimming

A standardized 200-m front crawl sprint swim (SpS) was used to evaluate the effects of warm-up on pH, blood gases, and the concentrations of lactate ([La-]) and bicarbonate ([HCO3-]) in arterialized and venous blood. Eight trained male swimmers performed two randomly assigned 200-m front crawl swims at previously determined intensities corresponding to 120% V̇O2max. One swim was preceded by a warm-up (WU trial) which consisted of a 400-m front crawl swim (82% V̇O2max), 400-m flutter kicking (45% V̇2max), and 4 × 50-m front crawl sprints (111% V̇2max). The second was performed without warm-up (NWU trial). Blood was sampled from a hyperemized earlobe and an antecubital vein before the warm-up, 9 min after the warm-up (1 min before the swim), immediately following the SpS, and at 2, 5, 10, and 20 min after the SpS. The warm-up exercise resulted in a higher pre-SpS [La-] in arterialized blood (3.1±0.4 and 1.7 ± 0.4 mmol × 1-1, p < 0.05), a higher hydrogen ion concentration ([H+]) in venous blood (45.9 ± 0.9 and 42.2 ± 0.8 nmol × 1-1, p < 0.001), and a lower arterialized blood [HCO3-] (25.1 ± 0.9 and 22.2 ± 0.8 mmol × 1-1, p < 0.05). The SpS was accompanied with higher heart rates during the WU trial (178 ± 3 and 169 ± 3 bpm; p < 0.05). After the SpS the absolute [La-] in arterialized blood was lower in the WU trial at 2 min of recovery (10.7 ± 0.6 and 12.8 ± 0.8 mmol × 1-1, p < 0.05). However, during the WU trial the increase in blood La (ΔLa) caused by the SpS was significantly lower at each stage for both blood compartments. Venous blood pCO2 was lower in the WU trial after the SpS (71.5 ± 3.0 and 78.4 ± 2.7 mmHg; p < 0.05), and the [H+ ] in venous blood was lower in the WU trial until 5 min of recovery (p < 0.05). These results indicate that warm-up exercise can reduce the disturbance in blood acid-base balance during 2 min of intense swimming. It is proposed that the acid-base differences resulted from increased oxidative energy metabolism and a subsequent reduction in lactate and CO2 production

Early effects of short-term aerobic training : physiological responses to graded exercise

Effets cardiorespiratoires (fréquence et débit cardiaque, lactate sanguin, consommation d'oxygène) et musculaires (EMG des muscles des jambes) d'un programme de trois semaines d'entraînement d'endurance sur bicyclette ergométrique chez des jeunes adultes sédentaire

Effects of warm-up on muscle glycogenolysis during intense exercise

This study investigated the effects of preliminary exercise (warm-up) on glycogen degradation and energy metabolism during intense cycle ergometer exercise. After determination of VO2max, six male subjects were randomly assigned to perform warm-up (WU) and no warm-up (NWU) trials incorporating a 2 min standardized sprint ride (SR) at 120 of the power output attained at VO2max (POmax). Muscle biopsies and temperature (Tm) recordings were obtained from the vastus lateralis muscle. Tm was elevated above the resting level prior to the SR during the WU trial (37.7 ± 0.1 vs 35.4 ± 0.4°C; P < 0.05) and remained higher than the NWU trial after the SR (38.6 ± 0.2 vs 37.1 ± 0.4°C; P < 0.05). Similar trends existed for rectal temperature (Tr). The increases in Tm and Tr during the SR were both greater in the NWU trial (P < 0.05). Muscle glycogen degradation was similar for the WU and NWU trials (30.8 ± 3.7 vs 25.6 ± 3.7 mmol-kg-1, respectively). When blood and muscle lactate concentrations after the SR were expressed relative to values before the SR, the WU trial resulted in a lower accumulation of blood lactate (6.5 ± 0.9 vs 10.7 ± 0.8 mEq 1-1; P < 0.01) and muscle lactate (20.1 ± 0.1 vs 23.4 ± 2.2 mEq . kg-1 wet wt.; P < 0.05). Furthermore, oxygen consumption during the 1st min of the SR was higher in the WU trial (2.3 ± 0.2 vs 1.9 ± 0.21-min-1; P < 0.05). The changes in Tm indicated a potential for a maintained active hyperemia in the vastus lateralis following the warm-up. These results suggest that a maintained active hyperemia following warm-up may improve blood flow at the onset of high intensity exercise and transiently increase the aerobic contribution to muscle energy metabolism. Nevertheless, warm-up did not spare muscle glycogen during intense exercise