The lactate paradox: a review

Nutrition and Hydration for High-Altitude Alpinism: A Narrative Review

This report aims to summarise the scientific knowledge around hydration, nutrition, and metabolism at high altitudes and to transfer it into the practical context of extreme altitude alpinism, which, as far as we know, has never been considered before in the literature. Maintaining energy balance during alpine expeditions is difficult for several reasons and requires a deep understanding of human physiology and the biological basis for altitude acclimation. However, in these harsh conditions it is difficult to reconcile our current scientific knowledge in sports nutrition or even for mountaineering to high-altitude alpinism: extreme hypoxia, cold, and the logistical difficulties intrinsic to these kinds of expeditions are not considered in the current literature. Requirements for the different stages of an expedition vary dramatically with increasing altitude, so recommendations must differentiate whether the alpinist is at base camp, at high-altitude camps, or attempting the summit. This paper highlights nutritional recommendations regarding prioritising carbohydrates as a source of energy and trying to maintain a protein balance with a practical contextualisation in the extreme altitude environment in the different stages of an alpine expedition. More research is needed regarding specific macro and micronutrient requirements as well as the adequacy of nutritional supplementations at high altitudes.

Single Leg Cycling Offsets Reduced Muscle Oxygenation in Hypoxic Environments

The intensity of large muscle mass exercise declines at altitude due to reduced oxygen delivery to active muscles. The purpose of this investigation was to determine if the greater limb blood flow during single-leg cycling prevents the reduction in tissue oxygenation observed during traditional double-leg cycling in hypoxic conditions. Ten healthy individuals performed bouts of double and single-leg cycling (4, four-minute stages at 50−80% of their peak oxygen consumption) in hypoxic (15% inspired O2) and normoxic conditions. Heart rate, mean arterial pressure, femoral blood flow, lactate, oxygenated hemoglobin, total hemoglobin, and tissue saturation index in the vastus lateralis were recorded during cycling tests. Femoral blood flow (2846 ± 912 mL/min) and oxygenated hemoglobin (−2.98 ± 3.56 au) during single-leg cycling in hypoxia were greater than double-leg cycling in hypoxia (2429 ± 835 mL/min and −6.78 ± 3.22 au respectively, p ≤ 0.01). In addition, tissue saturation index was also reduced in the double-leg hypoxic condition (60.2 ± 3.1%) compared to double-leg normoxic (66.0 ± 2.4%, p = 0.008) and single-leg hypoxic (63.3 ± 3.2, p < 0.001) conditions. These data indicate that while at altitude, use of reduced muscle mass exercise can help offset the reduction in tissue oxygenation observed during larger muscle mass activities allowing athletes to exercise at greater limb/muscle specific intensities.

Alterations in acid-base balance and high-intensity exercise performance after short-term and long-term exposure to acute normobaric hypoxic conditions

This investigation assessed the course of renal compensation of hypoxia-induced respiratory alkalosis by elimination of bicarbonate ions and impairments in anaerobic exercise after different durations of hypoxic exposure. Study A: 16 participants underwent a resting 12-h exposure to normobaric hypoxia (3,000 m). Blood gas analysis was assessed hourly. While blood pH was significantly increased, PO2, PCO2, and SaO2 were decreased within the first hour of hypoxia, and changes remained consistent. A substantial reduction in [HCO3-] levels was observed after 12 h of hypoxic exposure (- 1.35 ± 0.29 mmol/L, p ≤ 0.05). Study B: 24 participants performed in a randomized, cross-over trial portable tethered sprint running (PTSR) tests under normoxia and after either 1 h (n = 12) or 12 h (n = 12) of normobaric hypoxia (3,000 m). No differences occurred for PTSR-related performance parameters, but the reduction in blood lactate levels was greater after 12 h compared with 1 h (- 1.9 ± 2.2 vs 0.0 ± 2.3 mmol/L, p ≤ 0.05). These results indicate uncompensated respiratory alkalosis after 12 h of hypoxia and similar impairment of high-intensity exercise after 1 and 12 h of hypoxic exposure, despite a greater reduction in blood lactate responses after 12 h compared with 1 h of hypoxic exposure.

Serum Autofluorescence and Biochemical Markers in Athlete's Response to Strength Effort in Normobaric Hypoxia: A Preliminary Study

The human organism has the ability to adapt to hypoxia conditions. Training in hypoxia is used in sport to improve the efficiency of athletes; however, type of training affects the direction and scope of this process. Therefore, in this study, the usefulness of serum fluorescence spectroscopy to study the assessment of athlete's response to strength effort in hypoxia is considered in comparison with biochemical assay. Six resistance-trained male subjects took part in a research experiment. They performed barbell squats in simulated normobaric hypoxic conditions with deficiency of oxygen 11.3%, 13% 14.3% compared to 21% in normoxic conditions. Fluorescence intensity of tyrosine revealed high sensitivity on strength effort whereas tryptophan was more dependent on high altitude. Changes in emission in the visible region are associated with altering cell metabolism dependent on high altitude as well as strength training and endurance training. Significant changes in serum fluorescence intensity with relatively weak modifications in biochemical assay at 3000 m above sea level (ASL) were observed. Training at 5000 m ASL caused changes in fluorescence parameters towards the normobaric specific values, and pronounced decreases of lactate level and kinase creatine activity were observed. Such modifications of fluorescence and biochemical assay indicate increased adaptation of the organism to effort in oxygen-deficient conditions at 5000 m ASL, unlike 3000 m ASL. Fluorescence spectroscopy study of serum accompanied by biochemical assay can contribute to the understanding of metabolic regulation and the physiological response to hypoxia. The results of serum autofluorescence during various concepts of altitude training may be a useful method to analyze individual response to acute and chronic hypoxia. An endogenous tryptophan could be exploited as intrinsic biomarker in autofluorescence studies. However, these issues require further research.

A retrospective investigation of the impact of ‘eventing phase (dressage, show-jumping and cross-country)’ on pre-competition anxiety and self-confidence

Working in the discipline of eventing (the triathlon of equestrian sport), the present study aims to extend current literature on the use of psychological skills within equestrian sports, by understanding and identifying differences in levels of self-confidence and competitive anxiety. Each eventing phase (dressage, show-jumping and cross-country) was considered and its impact on anxiety and self-confidence analysed. Level of competition was considered a covariate and its effect on specific eventing phases and any associated influence on anxiety and self-confidence within eventing phase was analysed. An experimental, 3×3 factorial, within-subjects design was used. 57 participants (52 female and 5 male; 18 professional, 36 amateur and 3 undefined) completed the Revised Competitive Sport Anxiety Inventory 2 (CSAI-2R), a 17-item questionnaire measuring anxiety and self-confidence. Descriptive statistics identified the show-jumping phase had the largest impact on rider somatic anxiety (SA) and cognitive anxiety (CA). The cross-country phase had the highest self-confidence mean score. Spearman’s rank correlations showed both SA and CA were debilitative for all competition levels. Both SA and CA were found to be more debilitating in the show-jumping phase when self-confidence was low. MANCOVA analysis showed that eventing phase had significant effect on anxiety and self-confidence when controlling for level of competition. Dependent on the eventing phase riders are competing in, they experience different levels of arousal and self-confidence. When SA and CA are a debilitative source of anxiety, this could result in rider muscle tension which is not conducive to effective horse-rider communication. Coaches or sports psychologists should consider how to help riders manage their anxiety levels in relation to the competition phase, with the intention of enhancing self-confidence and enabling facilitative SA and CA in preparation for eventing performance.

A preliminary study investigating functional movement screen test scores in female collegiate age horse-riders

The functional movement screen (FMS) is an easily administered and non-invasive tool to identify areas of weakness and asymmetry during specific exercises. FMS is a common method of athlete screening in many sports and is used to ascertain injury risk, but has to be used within an equestrian population. The aim of this study was to establish FMS scores for female collegiate age (18-26 years) riders, to inform a normative data set of FMS scores in horse riders in the future. Thirteen female collegiate horse riders (mean ± standard deviation (sd); age 21.5±1.4 years, height 167.2±5.76 cm, mass 60.69±5.3 kg) and 13 female collegiate non-riders (mean ± sd; age 22.5±2.1 years, height 166.5±5.7 cm, mass 61.5±4.9 kg) were assessed based on their performance on a 7-point FMS (deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, trunk stability and rotary stability). The mean composite FMS scores (± sd) for the rider group was 14.15±1.9 and for the non-riders was 13.15±1.77. There was no statistically significant difference in median FMS composite scores between the rider and non-rider groups (Mann-Whitney U test, z=-1.249, P=0.223). However, 46% of riders and 69% of non-riders scored ≤14, indicating that a non-rider is 1.5 times (odds ratio) more likely to be at increased risk of injury compared to riders. Collegiate female riders scored higher than the non-rider population, but lower than seen in other sports suggesting some riders may be at risk of injury. Riders’ FMS scores demonstrated asymmetric movement patterns potentially limiting left lateral movement. Asymmetry has a potential impact on equestrian performance, limiting riders’ ability to apply the correct cues to the horse. The findings of such screening could inform the development of axillary training programmes to correct asymmetry pattern and target injury prevention.

Low dose of dichloroacetate infusion reduces blood lactate after submaximal exercise in horses

The acute administration of an indirect activator of the enzyme pyruvate dehydrogenase (PDH) in human athletes causes a reduction in blood lactate level during and after exercise. A single IV dose (2.5m.kg-1) of dichloroacetate (DCA) was administered before a submaximal incremental exercise test (IET) with five velocity steps, from 5.0 m.s-1 for 1 min to 6.0, 6.5, 7.0 and 7.5m.s-1 every 30s in four untrained mares. The blood collections were done in the period after exercise, at times 1, 3, 5, 10, 15 and 20 min. Blood lactate and glucose (mM) were determined electro-enzymatically utilizing a YSI 2300 automated analyzer. There was a 15.3% decrease in mean total blood lactate determined from the values obtained at all assessment times in both trials after the exercise. There was a decrease in blood lactate 1, 3, 5, 10, 15 and 20 min after exercise for the mares that received prior DCA treatment, with respective mean values of 6.31±0.90 vs 5.81±0.50, 6.45±1.19 vs 5.58±1.06, 6.07±1.56 vs 5.26±1.12, 4.88±1.61 vs 3.95±1.00, 3.66±1.41 vs 2.86±0.75 and 2.75±0.51 vs 2.04±0.30. There was no difference in glucose concentrations. By means of linear regression analysis, V140, V160, V180 and V200 were determined (velocity at which the rate heart is 140, 160, 180, and 200 beats/minute, respectively). The velocities related to heart rate did not differ, indicating that there was no ergogenic effect, but prior administration of a relatively low dose of DCA in mares reduced lactatemia after an IET.