Effect of an acute beta-adrenergic blockade on the blood glucose response during lactate minimum test

DETERMINATION OF INDIVIDUAL GLUCOSE THRESHOLD USING PHARMACY PORTABLE BLOOD GLUCOSE METER

ABSTRACT Introduction The individual glucose threshold (IGT) has been used to estimate the anaerobic threshold with low-cost analyses and shorter times. However, the reliability of the glycemic analysis using a portable pharmacy glucose meter has received little attention. Objective To identify the IGT using a portable glucose meter and to compare it with the ventilatory threshold (VT). Methods Fourteen active, healthy men (25.9 ± 3.2 years; %BF = 17.9 ± 3.7%) performed an incremental treadmill test. The anaerobic threshold was identified by two different methods: (1) IGT, corresponding to the intensity of the lowest glucose value during the test; and (2) VT, corresponding to the break in linearity of the ventilation curve and an increase in the respiratory oxygen equivalent, without an equivalent increase in carbon dioxide. Results There were significant differences between VT (9.9 ± 1.2 km/h) and IGT (9.5 ± 1/1 km/h), corresponding to 75.4 ± 9.2 and 72.5 ± 10.4 %VO2max, respectively. The methods presented high correlation (r = 0.82, p = 0.002) and the Bland-Altman technique showed agreement between IGT and VT, with a mean difference of 0.5 km/h. Conclusion It was possible to determine the intensity of IGT by the glycemic response in the incremental test using a portable glucose meter. The IGT underestimated the intensity of VT by approximately 0.5 km/h, but with a high correlation and agreement between them. Level of evidence III, Case-Controle Study.

Moderate physical activity from childhood contributes to metabolic health and reduces hepatic fat accumulation in adult rats

BACKGROUND

Obesity, oxidative stress and inflammation, by triggering insulin resistance, may contribute to the accumulation of hepatic fat, and this accumulation by lipotoxicity can lead the organ to fail. Because obesity is growing at an alarming rate and, worryingly, in a precocious way, the present study aimed to investigate the effects of moderate physical training performed from childhood to adulthood on liver fat metabolism in rats.

METHODS

Twenty rats that were 28 days old were divided into two groups: control (C) and trained (T). The C Group was kept in cages without exercise, and the T group was submitted to swimming exercise for 1 hour/day, 5 days/week from 28 to 90 days of age (8 weeks) at 80% of the anaerobic threshold determined by the lactate minimum test. At the end of the experiment, the body weight gain, insulin sensitivity (glucose disappearance rate during the insulin tolerance test), concentrations of free fatty acids (FFA) and triglycerides (TG) and hepatic lipogenic rate were analyzed. For the statistical analysis, the Student t-test was used with the level of significance preset at 5%.

RESULTS

The T group showed lower body weight gain, FFA concentrations, fat accumulation, hepatic lipogenic rate and insulin resistance.

CONCLUSION

The regular practice of moderate physical exercise from childhood can contribute to the reduction of obesity and insulin resistance and help prevent the development of accumulation of hepatic fat in adulthood.

Usefulness of the serum lactate concentration for predicting mortality in acute beta-blocker poisoning

CONTEXT

Serum lactate measured in the emergency department was recently assessed as an excellent prognosticator of drug-overdose fatality, with the optimal lactate cutoff point being 3.0 mmol/L. However, lactate's role has never been specifically studied in beta-blocker poisonings.

OBJECTIVE

We aimed to evaluate the ability of lactate concentrations to predict outcome (survival versus death) in beta-blocker poisoning.

METHODS

We conducted an 8-year retrospective study for all symptomatic beta-blocker poisonings admitted to our toxicological intensive care unit (ICU). Serum lactate concentrations were measured in 110 patients and final outcomes of survival or death recorded.

RESULTS

Lactate concentrations were 1.79 mmol/L [0.8-5.6] (median, 10-90% percentiles) and peak values of 1.9 mmol/L [0.9-9.5] (p < 0.0001). Nine patients (8%) died in the ICU. Admission serum lactate concentrations differed significantly between survivors and fatalities (p = 0.0008). Four patients (44% of the non-survivors) died in the ICU despite lactate concentrations lower than 3.0 mmol/L. The diagnostic characteristics of the 3.0 mmol/L selected lactate cutoff point were 55% sensitivity and 80% specificity.

CONCLUSION

Serum lactate elevation in beta-blocker poisoning is relatively mild on admission despite the presence of significant cardiovascular symptoms. Even if raised in severe poisonings and alone correlate well with prognosis, lactate concentration is not an absolute predictor of beta-blocker-overdose fatality.

Lactate threshold prediction by blood glucose and rating of perceived exertion in people with type 2 diabetes

The validity of rating of perceived exertion (RPE) in predicting lactate threshold during an incremental test was analyzed in 15 men with type 2 diabetes (M age = 53.4 yr., SD = 12.9). Blood glucose, lactate, and minute ventilation (VE)/VO2 responses identified the lactate, ventilatory, and glucose thresholds. Workloads (W) corresponding to RPEs 12, 13, 14, and 15 were determined. Second-order polynomials fit to VE/W and [lac]/W ratios corresponding to RPEs of 9-10, 12-13, and 16-17 also identified workloads above which there was an overproportional increase in VE and [lac]. These workload breakpoints did not differ, although at RPE 12 underestimated and at RPE 15 overestimated lactate threshold. RPE 13 and 14 and the responses of VE/W and [lac]/W to submaximal exercise accurately predicted lactate threshold.

Influence of recovery manipulation after hyperlactemia induction on the lactate minimum intensity

This study analyzed the influence of recovery phase manipulation after hyperlactemia induction on the lactate minimum intensity during treadmill running. Twelve male runners (24.6 +/- 6.3 years; 172 +/- 8.0 cm and 62.6 +/- 6.1 kg) performed three lactate minimum tests involving passive (LMT(P)) and active recoveries at 30%vVO(2max) (LMT(A30)) and 50%vVO(2max) (LMT(A50)) in the 8-min period following initial sprints. During subsequent graded exercise, lactate minimum speed and VO(2) in LMT(A50) (12.8 +/- 1.5 km h(-1) and 40.3 +/- 5.1 ml kg(-1) min(-1)) were significantly lower (P < 0.05) than those in LMT(A30) (13.3 +/- 1.6 km h(-1) and 42.9 +/- 5.3 ml kg(-1) min(-1)) and LMT(P) (13.8 +/- 1.6 km h(-1) and 43.6 +/- 6.1 ml kg(-1) min(-1)). In addition, lactate minimum speed in LMT(A30) was significantly lower (P < 0.05) than that in LMT(P). These results suggest that lactate minimum intensity is lowered by active recovery after hyperlactemia induction in an intensity-dependent manner compared to passive recovery.

Identificação do limiar de lactato e limiar glicêmico em exercícios resistidos

Com o objetivo de analisar a possibilidade de identificar o limiar glicêmico (LG), bem como comparar e correlacionar as intensidades dos limiares glicêmico e de lactato (LL) em exercícios resistidos incrementais, 12 voluntários do sexo masculino (24,4 ± 1,2 anos) adaptados ao exercício resistido foram submetidos a testes incrementais realizados nos exercícios leg press 45º (LP) e supino reto (SR). As intensidades aplicadas nos estágios incrementais de 1 min foram de 10%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80% e 90% da carga máxima (1RM) determinada anteriormente, ou até a exaustão voluntária. As coletas sanguíneas para as dosagens das concentrações de lactato e glicose sanguínea foram realizadas durante os 2 min de pausa entre os estágios (YSI 2300 S). O comportamento da glicemia e lactatemia foram similares em ambos os exercícios estudados. Não foram encontradas diferenças significativas (p > 0,05) entre as percentuais de 1RM nos limiares lactatêmicos e glicêmicos observados, respectivamente, no LP (36,6 ± 1,4% e 32,9 ± 1,5%) e SR (31,2 ± 1,2% e 31,2 ± 1,8%). Alta correlação foi observada entre os limiares glicêmico e lactatêmico identificados tanto no LP (r = 0,80; p < 0,001) quanto no SR (r = 0,73; p < 0,006). Concluiu-se que foi possível identificar os limiares de lactato e glicêmico em exercícios resistidos incrementais. No entanto, o significado desses limiares bem como sua validade para avaliação funcional e prescrição de exercícios devem ser melhor investigados.

Lactate and glucose minimum speeds and running performance

This study aimed to analyse the validity of glucose minimum speed (GMS) for lactate minimum speed (LMS) assessment during running and their relationship to endurance performance. Eight male trained runners (28.7 +/- 9.0 years) volunteered to take part in this study and underwent an official 10-km road race and a track lactate minimum test (LMT) (0.5-km sprint plus 6 x 800 m from 87 to 98% of maximal 3-km speed). Lactate and glucose minimum speeds were considered those related to the minimum blood lactate and glucose concentrations respectively attained during the graded phase of LMT. Significant correlations (p < 0.05) were found between LMS and GMS (r = 0.72) and LMS and 10-km performance (r = 0.83), but not between GMS and 10-km performance (r = 0.49). No significant differences (p > 0.05) were found between LMS (4.75 +/- 0.08 m/s), GMS (4.73 +/- 0.07 m/s) and 10-km mean speed (4.79 +/- 0.17 m/s). In conclusion, we found GMS to be a good predictor of LMS during track LMT, LMS being well related to endurance running performance.