Combined spiroergometry and 31P–MRS of human calf muscle during high‐intensity exercise

Simultaneous measurements of pulmonary oxygen consumption (VO₂), carbon dioxide exhalation (VCO₂) and phosphorus magnetic resonance spectroscopy (³¹P–MRS) are valuable in physiological studies to evaluate muscle metabolism during specific loads. Therefore, the aim of this study was to adapt a commercially available spirometric device to enable measurements of VO₂ and VCO₂ whilst simultaneously performing ³¹P–MRS at 3 T. Volunteers performed intense plantar flexion of their right calf muscle inside the MR scanner against a pneumatic MR‐compatible pedal ergometer. The use of a non‐magnetic pneumotachograph and extension of the sampling line from 3 m to 5 m to place the spirometric device outside the MR scanner room did not affect adversely the measurements of VO₂ and VCO₂. Response and delay times increased, on average, by at most 0.05 s and 0.79 s, respectively. Overall, we were able to demonstrate a feasible ventilation response (VO₂ = 1.05 ± 0.31 L/min; VCO₂ = 1.11 ± 0.33 L/min) during the exercise of a single calf muscle, as well as a good correlation between local energy metabolism and muscular acidification (τ_{PCr fast} and pH; R² = 0.73, p < 0.005) and global respiration (τ_{PCr fast} and VO₂; R² = 0.55, p = 0.01). This provides improved insights into aerobic and anaerobic energy supply during strong muscular performances.     

Comparison of metabolic adaptations between endurance‐ and sprint‐trained athletes after an exhaustive exercise in two different calf muscles using a multi‐slice 31P‐MR spectroscopic sequence

Measurements of exercise‐induced metabolic changes, such as oxygen consumption, carbon dioxide exhalation or lactate concentration, are important indicators for assessing the current performance level of athletes in training science. With exercise‐limiting metabolic processes occurring in loaded muscles, ³¹P‐MRS represents a particularly powerful modality to identify and analyze corresponding training‐induced alterations. Against this background, the current study aimed to analyze metabolic adaptations after an exhaustive exercise in two calf muscles (m. soleus – SOL – and m. gastrocnemius medialis – GM) of sprinters and endurance athletes by using localized dynamic ³¹P‐MRS. In addition, the respiratory parameters VO₂ and VCO₂, as well as blood lactate concentrations, were monitored simultaneously to assess the effects of local metabolic adjustments in the loaded muscles on global physiological parameters. Besides noting obvious differences between the SOL and the GM muscles, we were also able to identify distinct physiological strategies in dealing with the exhaustive exercise by recruiting two athlete groups with opposing metabolic profiles. Endurance athletes tended to use the aerobic pathway in the metabolism of glucose, whereas sprinters produced a significantly higher peak concentration of lactate. These global findings go along with locally measured differences, especially in the main performer GM, with sprinters revealing a higher degree of acidification at the end of exercise (pH 6.29 ± 0.20 vs. 6.57 ± 0.21). Endurance athletes were able to partially recover their PCr stores during the exhaustive exercise and seemed to distribute their metabolic activity more consistently over both investigated muscles. In contrast, sprinters mainly stressed Type II muscle fibers, which corresponds more to their training orientation preferring the glycolytic energy supply pathway. In conclusion, we were able to analyze the relation between specific local metabolic processes in loaded muscles and typical global adaptation parameters, conventionally used to monitor the training status of athletes, in two cohorts with different sports orientations.     

A study of the SCN5A gene in a cohort of 76 patients with Brugada syndrome

We aim to study the SCN5A gene in a cohort of Brugada syndrome (BS) patients and evaluate the genotype–phenotype correlation. BS is caused by mutations in up to 10 different genes, SCN5A being the most frequently involved. Large genomic rearrangements in SCN5A have been associated with conduction disease, but its prevalence in BS is unknown. Seventy‐six non‐related patients with BS were studied. Clinical characteristics and family risk profile were recorded. Direct sequencing and multiplex ligation‐dependent probe amplification (MLPA) of the SCN5A gene for identification of mutations and larger rearrangements were performed, respectively. Eight patients (10.5%) had point mutations (R27H, E901K, G1743R (detected in three families), V728I, N1443S and E1152X). Patients with mutations had a trend toward a higher proportion of spontaneous type I Brugada electrocardiogram (ECG) (87.5% vs 52.9%, p = 0.06) and had evidence of familial disease (62.5%, vs 23.5%, p = 0.03). The symptoms and risk profile of the carriers were not different from wild‐type probands. There were non‐significant differences in the prevalence of type I ECG, syncope and history of arrhythmia in carriers of selected polymorphisms. None of the patients had any deletion/duplication in the SCN5A gene. In conclusion, 10.5% of our patients had mutations in the SCN5A gene. Patients with mutations seemed to have more spontaneous type I ECG, but no differences in syncope or arrhythmic events compared with patients without mutations. Larger studies are needed to evaluate the role of polymorphisms in the SCN5A in the expression of the phenotype and prognosis. Large rearrangements were not identified in the SCN5A gene using the MLPA technique.