Jesús Álvarez-Herms

Popularity of hypoxic training methods for endurance-based professional and amateur athletes.

Scientific debate continues into whether hypoxic training has any performance benefit for athletes, and although this type of training seems popular, to our knowledge little empirical evidence on its popularity with endurance-based athletes exists. To quantify the usage of hypoxic training in endurance-based athletes we asked 203 athletes (amateur = 108, professional = 95) to complete a 17-question survey during 2013-2014 season. Compared to amateurs, professional athletes were 4.5 times (3.0-6.8, odds ratio, 95% confidence limits) more likely to undertake hypoxic training. Live-high train-low was the most popular hypoxic training protocol for athletes (52% professional and 80% amateur) with live-high train-high also used (38% professional, 20% amateur). Compared to amateurs, professional athletes tended to use evidence-based hypoxic training methods, seek advice on hypoxic training from reliable sources and were generally more realistic about the potential performance gains as a result of hypoxic training. Almost one third (25-30%) of all athletes suffered illness during their hypoxic training. Compared to amateurs, professional athletes are more likely to undertake hypoxic training and tend to follow current scientific guidelines. Attenuation of the ill effects that occur during hypoxic training may be accomplished if athletes give more attention to monitoring stress and training levels.

The influence of dental occlusion on the body balance in unstable platform increases after high intensity exercise.

Existing evidence suggests that body balance ability is associated with dental occlusion. The purpose of this study was to determine whether: (i) there are differences in balance between opposed dental occlusion (intercuspal position, ICP; cotton rolls, CR) for two extreme levels of stability and (ii) the influence of dental occlusion on the balance control gets stronger under fatigue conditions. To this aim, various measures for assessing postural control in ten physically active subjects were obtained prior to and following a maximal lower limbs exercise consisting in six sets of fifteen seconds stretch-shortening cycle jumping. Balance control at stable and unstable condition was evaluated on an unstable platform Balance System SD for both dental occlusion conditions at random order. Metabolic and psychological measurements ensured the high intensity of the exercise. At unstable level, balance control was significantly improved in the CR condition, for both rest (p=0.03) and fatigue (p<0.001). Whereas at stable level, the influence of dental occlusion only reached significance in fatigue condition (p=0.04). It could be concluded that the sensory information linked to the dental occlusion for the balance control comes strongly into effect when more difficult conditions for the balance control are present (i.e., unstable conditions, fatigue).

Strength training under hypoxic conditions

Recently, Kon et al. (5) published in this journal an interesting paper entitled “Effects of systemic hypoxia on human muscular adaptations to resistance exercise training “ which determined the effect of 8 weeks of resistance training (5 sets of 10 reps at 70% of 1 RM of free weight bench‐press and bilateral leg‐press using a weight‐stack machine) under hypoxia (HRT, 14.4% O2) or normoxia, on muscle cross‐sectorial area, 1 RM, muscular endurance and markers of mitochondrial biogenesis and angiogenesis. Their conclusion suggested two important findings: (1) an increased muscular endurance and, (2) the promotion of angiogenesis in skeletal muscle in the hypoxic‐trained subjects compared to the normoxic‐trained subjects. However, in our opinion, a number of the comments in the Kon et al. (5) publication need clarification, moreover, the authors conclusions may only partially explain the benefits of resistance training in hypoxia for endurance athletes. In the discussion section, the authors state: “For the first time, we demonstrate a significant resistance‐training‐induced increase in muscular endurance in the …

Exercise and oral health: Implications of the exercise intensity on dental diseases

The higher risk of oral diseases related to exercise, such as dental erosion or tooth decay, is a matter of clinical interest. However, in our opinion, scientists should be more accurate when referring to exercise-related risk. The well-known physiological differences between aerobic and anaerobic exercises are often not appropriately addressed in the oral science area. The exercise intensity and duration are related with the use of different metabolic pathways that elicit different responses not only at the whole body level but also on the oral cavity. Recently, Frese et al. (2014) published in this journal an interesting paper entitled “Effect of endurance training on dental erosion, caries, and saliva.” This is a clinical research developing the hypothesis that endurance training could affect oral health. The main body of the document comprises a questionnaire about training habits and sport nutrition in a sample of 35 triathletes and 35 non-exercising controls. The authors conclude that athletes experience an increased risk for dental erosion and caries prevalence. In addition, authors evaluated the saliva pH after an incremental running field test at maximal workload reporting a decrease in saliva flow rates and an increase in saliva pH in comparison with measurements 5 min before. In this regard, we observed that saliva pH increased after maximal anaerobic running field test until exhaustion (Julià-Sánchez et al., 2013). The similar trend to increase in blood lactate and saliva pH then led us to speculate that saliva pH could be related to exercise intensity as other salivary constituents like salivary lactate (Segura et al., 1996), α-amylase (Chicharro et al., 1998), or the total protein concentration do (Bortolini et al., 2009). To test the hypothesis of this correlation, we assessed changes in saliva pH after performing a countermovement jump exercise in hypoxia and normoxia. It is well known that hypoxia is a stress factor because the additional oxygen debt increases the exercise intensity (Levine et al., 1992). Only for the hypoxia conditions (2.500 and 4.000 m) we observed not only an increase on the saliva pH but also a significant correlation with the SaO2, thus reinforcing our previous hypothesis (Julià-Sánchez et al., 2014). As suggested by the authors, the increase in saliva pH could be due to a compensatory reaction in order to balance prior deficit of saliva. However, other causes should be taken into account. More specifically, there are some data to suggest that this possible relationship could be due to an increase in the buffer capacity after performing incremental anaerobic exercise (Nakagawa et al., 1996) or to an alteration in the reabsorptive and secretory mechanisms following the decrease of salivary gland blood supply (Chicharro et al., 1999). The authors concluded by saying that: “. . . Higher risk for dental erosions, exercise dependent caries risk, and load-dependent changes in saliva parameters point out the need for risk-adapted preventive dental concepts in the field of sports dentistry.” However, we postulate that an important consideration for Sports Dentistry experts should be also to discern aerobic from anaerobic exercise. The low DMFT (decayed-missing-filled tooth) index (2.83 ± 3.71) reported in our sample of anaerobic discipline athletes (Julià-Sánchez et al., 2013) calls into question the dental disease risk related to exercise. Since salivary responses reported after performing aerobic and anaerobic exercises quite differ at qualitative and quantitative levels, a more cautious position is necessary when talking about the caries risk and exercise. Moreover, it is well known that saliva pH is highly linked to caries development (Stephan, 1944), thus the increase of saliva pH after performing anaerobic exercise should require more interest and future study. In light of the above considerations, we consider that the conclusions presented in the paper of Frese et al. require a more prudent analysis (discerning between aerobic or anaerobic exercise). Therefore, whether exercise-related risk on oral health is predominantly concerning aerobic exercise remains an open question.