Efeitos de variações metodológicas sobre a identificação do lactato mínimo

The aim of this study was to analyze the influence of increment pattern as well as the stage duration on lactate minimum (LM) determination. Volunteers were eight physical active males [22.4 + 1.9 years; 177 ± 4.2 cm; 73.6 ± 5.4 kg; 23,4 ± 1,3 kg.(m2)-1] that performed, on different days, two incremental tests on cycle ergometer after lactic acidosis induction through 30 seconds Wingate test. Test 1- initial load of 1.75 kp and increments of 0.25 kp at each stage of 3 min until volitional exhaustion to determine the intensity corresponding to LM (LM1); Test 2- the intensities were 0.5 kp below, 0.5 kp above and the intensity at LM1 (at), the test 2 was composed by two parts (2a - stages of 3 min and 2b - stages of 6 min). The lactate concentration ([lac]), heart rate (HR) and exercise intensities corresponding to LM observed during parts 2a (LM2a) and 2b (LM2b) were compared to LM1. Differences were observed between the [lac] corresponding to LM1 and LM2a (4.9 ± 2.4 vs 6.2 ± 1.9 mM), as well as between the HR corresponding to LM2b (167 ± 14 bpm) and the HR corresponding to LM1 (159 ± 17 bpm) and LM2a (158 ± 12 bpm) (p < 0.05). However, no differences were observed for the intensities corresponding to LM1, LM2a and LM2b (2.6 ± 0.3 vs 2.6 ± 0.5 vs 2.6 ± 0.3 kp, respectively). We concluded that the methodological variations applied on present study did not interfere on the exercise intensity corresponding to LM.O objetivo do presente estudo foi analisar a influência de diferentes intensidades e durações de estágios incrementais sobre a determinação do lactato mínimo (LM). Fizeram parte deste estudo oito homens fisicamente ativos [22,4 ± 1,9 anos; 177,0 ± 4,2 cm; 73,6 ± 5,4 kg; 23,4 ± 1,3 kg&#9679;(m²)-1] que realizaram, em dias diferentes, dois testes incrementais em cicloergômetro após hiperlactacidemia induzida por um teste de Wingate de 30 segundos. Teste 1- carga inicial de 1,75 kp e incrementos de 0,25 kp a cada estágio de três minutos até exaustão voluntária para determinar a intensidade correspondente ao LM (LM1). Teste 2- alternando-se as cargas entre 0,5 kp abaixo, 0,5 kp acima e na intensidade do LM1, o teste 2 foi composto por duas partes seqüenciais (2a - estágios de três minutos e 2b - estágios de seis minutos). As concentrações de lactato sangüíneo ([lac]), freqüência cardíaca (FC) e intensidades (int) correspondentes ao LM dos testes 2a (LM2a) e 2b (LM2b) foram comparadas com o LM1. Foram observadas diferenças entre as [lac] correspondentes ao LM1 e LM2a (4,9 ± 2,4 vs 6,2 ± 1,9 mM) bem como entre a FC correspondente ao LM2b (167 ± 14 bpm) e os valores de FC correspondentes ao LM1 (159 ± 17 bpm) e LM2a (158 ± 12 bpm) (p < 0,05). Contudo, não foram observadas diferenças entre as int correspondentes ao LM1, LM2a e LM2b (2,6 ± 0,3 vs 2,6 ± 0,5 vs 2,6 ± 0,3 kp, respectivamente). Concluímos que as variações metodológicas empregadas não resultaram em alterações na intensidade de exercício correspondente ao LM

Aerobic Fitness Evaluation during Walking Tests Identifies the Maximal Lactate Steady State

Objective. The aim of this study was to verify the possibility of lactate minimum (LM) determination during a walking test and the validity of such LM protocol on predicting the maximal lactate steady-state (MLSS) intensity. Design. Eleven healthy subjects (24.2 ± 4.5 yr; 74.3 ± 7.7 kg; 176.9 ± 4.1 cm) performed LM tests on a treadmill, consisting of walking at 5.5 km · h−1 and with 20–22% of inclination until voluntary exhaustion to induce metabolic acidosis. After 7 minutes of recovery the participants performed an incremental test starting at 7% incline with increments of 2% at each 3 minutes until exhaustion. A polynomial modeling approach (LMp) and a visual inspection (LMv) were used to identify the LM as the exercise intensity associated to the lowest [bLac] during the test. Participants also underwent to 2–4 constant intensity tests of 30 minutes to determine the MLSS intensity. Results. There were no differences among LMv (12.6 ± 1.7%), LMp (13.1 ± 1.5%), and MLSS (13.6 ± 2.1%) and the Bland and Altman plots evidenced acceptable agreement between them. Conclusion. It was possible to identify the LM during walking tests with intensity imposed by treadmill inclination, and it seemed to be valid on identifying the exercise intensity associated to the MLSS

Acute exercise performed close to the anaerobic threshold improves cognitive performance in elderly females

The objective of the present study was to compare the effect of acute exercise performed at different intensities in relation to the anaerobic threshold (AT) on abilities requiring control of executive functions or alertness in physically active elderly females. Forty-eight physically active elderly females (63.8 ± 4.6 years old) were assigned to one of four groups by drawing lots: control group without exercise or trial groups with exercise performed at 60, 90, or 110% of AT (watts) and submitted to 5 cognitive tests before and after exercise. Following cognitive pretesting, an incremental cycle ergometer test was conducted to determine AT using a fixed blood lactate concentration of 3.5 mmol/L as cutoff. Acute exercise executed at 90% of AT resulted in significant (P < 0.05, ANOVA) improvement in the performance of executive functions when compared to control in 3 of 5 tests (verbal fluency, Tower of Hanoi test (number of movements), and Trail Making test B). Exercising at 60% of AT did not improve results of any tests for executive functions, whereas exercise executed at 110% of AT only improved the performance in one of these tests (verbal fluency) compared to control. Women from all trial groups exhibited a remarkable reduction in the Simple Response Time (alertness) test (P = 0.001). Thus, physical exercise performed close to AT is more effective to improve cognitive processing of older women even if conducted acutely, and using a customized exercise prescription based on the anaerobic threshold should optimize the beneficial effects

Suplementação de monoidrato de creatina: efeitos sobre a composição corporal, lactacidemia e desempenho de nadadores jovens

In order to verify the effects of oral Cr supplementation on performance, peak blood lactate (lac) levels and lean-fat body composition were determined for twelve young swimmers (15.1+1.1 years; 58.7+7.0 kg). Two groups were randomly assigned: supplemented group (SG, n=6) and control group (CG, n=6). For five days both groups received the following supplementation four times a day: 5g Cr + 50g of maltodextrine for SG and 50g of maltodextrine only for CG. The time and lac were measured before and after a five-day period of supplementation, and after a crawl-style swimming test: 1) 2x25m with 30-second rest, 2) 2x100m with 2-minute rest and 3) 1x700m trial. Bio impedance was applied for body composition, and sum of skin folds was determined before and after supplementation. Significant increase on the fat free mass of 1.0 (+0.4) kg with total body water retention of 1.5 (+0.5) liters was observed only for SG (p< .05). In fact, the increase in fat free mass may be due to the Cr-induced body water retention. No differences were found for the time and lac in aerobic and anaerobic exercises. We concluded that Cr supplementation for young swimmers (20g Cr/day for 5 days) increases fat free mass with no impact on performance.Com o objetivo de investigar os efeitos da administração oral de Cr sobre o desempenho, pico de lactato sangüíneo (lac), e composição corporal (CC), 12 nadadores jovens (15,1+1,1 anos; 58,7+7,0 Kg) foram divididos em grupos suplementado (GS, n=6) e controle (GC, n=6). Durante 5 dias, 4 vezes ao dia, administrou-se suplementação de 5g de Cr+50g de maltodextrina para o GS, e apenas 50g de maltodextrina para GC. Tempo e lac foram mensurados pré e pós período de suplementação, nos seguintes testes de nado crawl: 1) 2x 25m, com 30 seg. de pausa, 2) 2x100m com 2min. de pausa, e 3) 1x700m. A CC foi determinada por bioimpedância, e somatório de dobras cutâneas também foi realizado pré e pós suplementação. Não foram observadas diferenças significativas para o tempo e lac em exercícios aeróbios e anaeróbios após suplementação para ambos os grupos. Verificou-se, para GS, retenção hídrica corporal de 1,5 (+0,5) litros e conseqüente aumento de 1,0 (+0,4) Kg na massa magra (p< 0,05), porém sem efeito significativo sobre o desempenho e lac em nadadores jovens

Hipotensão pós-exercício: possível relação com fatores étnicos e genéticos

A hipotensão pós-exercício (HPE) caracteriza-se pela redução dos valores pressóricos em relação ao pré-exercício, sendo intensamente estudada em diferentes populações a partir das diversas modalidades de exercício físico. Inúmeros mecanismos relacionam-se à HPE, tornando-a de origem multifatorial. No entanto, na última década, alguns estudos objetivaram investigar possíveis influências de fatores étnicos e genéticos sobre a HPE. Nesse sentido, o objetivo do presente estudo foi revisar os fatores ambientais e principalmente, os étnicos e genéticos relacionados à HPE. Os estudos utilizados nesta revisão de literatura foram obtidos a partir de um levantamento bibliográfico realizado nos seguintes bancos de dados disponíveis na internet: Medline,SciELO e Portal Capes. Com relação à etnia, verifica-se que os estudos apontam desfavorável tendência aos indivíduos negros em obter HPE quando comparados aos de etnia branca, embora ainda não seja possível afirmar de maneira categórica. Quanto aos estudos genéticos e HPE, ressalta-se a importância destes estudos, assim como a necessidade de que a seleção dos genes candidatos à investigação seja feita baseando-se no sistema fisiológico implicado na regulação da pressão arterial. Basicamente, os estudos publicados analisaram a relação entre HPE e mutações de genes que expressam proteínas envolvidas no sistema renina-angiotensina-aldosterona. Nesse sentido, parece que o maior decaimento da PA ocorre, principalmente, após exercícios aeróbios de baixa intensidade realizados por homens adultos e normotensos limítrofes ou hipertensos, sendo necessários mais estudos acerca do tema. _________________________________________________________________________________________ ABSTRACT: Post-exercise hypotension (PEH) is characterized by a decrease in blood pressure (BP) in relation to pre-exercise levels and has been intensively studied in different populations after different modes of exercise. Several mechanisms are associated with PEH, which makes it a multifactorial condition. However, over the last decade, some studies aimed to investigate the possible influence of ethnic and genetic factors on PEH. Thus, the purpose of this study was to review the environmental and, mainly, ethnic and genetic factors related to PEH. The studies used herein were obtained from a review of the following online databases: MEDLINE, SciELO and, Portal Capes. In relation to ethnicity, studies appear to indicate an unfavorable trend toward development of PEH in blacks as compared to whites, although this cannot be stated categorically. As for genetic studies and PEH, we stress the importance of these studies and highlight the need for selecting candidate genes for research on the basis of the physiological system implicated in BP regulation. Published studies have basically examined the relationship between PEH and mutations in genes that express proteins involved in the renin-angiotensin-aldosterone system. In this genetic sense, it seems that the greatest decline in PA occurs mainly after low-intensity aerobic exercise performed by normotensive or borderline hypertensive adult men. Further studies on the subject are required

Combined exercise circuit session acutely attenuates stress-induced blood pressure reactivity in healthy adults

Objective: To investigate the blood pressure (BP) responses to cardiovascular stress test after a combined exercise circuit session at moderate intensity. Method: Twenty individuals (10 male/10 fem; 33.4± 6.9 years; 70.2± 15.8 kg; 170.4± 11.5 cm; 22.3± 6.8% body fat) were randomized in a different days to control session with no exercise or exercise session consisting of 3 laps of the following circuit: knee extension, bench press, knee flexion, rowing in the prone position, squats, shoulder press, and 5 min of aerobic exercise at 75-85% of age-predicted maximum heart rate and/or 13 on the Borg Rating of Perceived Exertion [scale of 6 to 20]. The sets of resistance exercise consisted of 15 repetitions at ~50% of the estimated 1 repetition maximum test. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured at rest and during 1h of recovery in both experimental sessions. After that, blood pressure reactivity (BPR) was evaluated using the Cold Pressor Test. Results: During 1h of exercise recovery, there was a reduction in SBP (3-6 mmHg) and DBP (2-5 mmHg) in relation to pre-session rest (p<0.01), while this reduction was not observed in the control session. A decline in BPR (4-7 mmHg; p<0.01) was observed 1h post-exercise session, but not in the control session. Post-exercise reductions in SBP and DBP were significantly correlated with BPR reductions (r=0.50-0.45; p<0.05). Conclusion: A combined exercise circuit session at moderate intensity promoted subsequent post-exercise hypotension and acutely attenuated BPR in response to a cardiovascular stress test. In addition, the post-exercise BP reduction was correlated with BPR attenuation in healthy adults of both genders

Determination of the anaerobic threshold by blood lactate and glucose measurements in track tests for runners

In order to compare the Anaerobic Threshold (AT) determined by blood lactate (lac) and to verify the possibility of AT determination by blood glucose (gluc) measurements, 12 male endurance runners (aged 25.5 + 7.0) performed four running track tests: a) 3.000 m performance (Vm3Km); b) equilibrium point between lac production and removal (Lacmin): 1 x maximal 500 m followed by 6 x 800 m progressive bouts (87 to 98% of Vm3Km) with 45 sec rest. The velocity (vel) associated with lower [lac] was considered as AT; c) individual anaerobic threshold (IAT): 8 x 800 m progressive bouts (84 to 102% of Vm3Km), with 45 sec rest. The AT vel was determined considering lac kinetic during the test and recovery; d) AT of [4 mM] lac (Vel4mM): Interpolation between lac and vel in 2 x 1200 m at 85 and 100% of Vm3Km, with 10 minutes rest; e) the vel associated at lower glue during IAT ( 0.05; see table below). IAT Lacmin Vel4m

Relação entre velocidade crítica, limiar anaeróbio, parâmetros associados ao VO2max, capacidade anaeróbia e custo de O2 submáximo

The purposes of the study were to compare and correlate the running velocities associated with the maximal oxygen consumption (Vmax), anaerobic threshold (LL), ventilatory threshold (LV), critical velocity (CV), anaerobic work capacity (AWC) and oxygen cost during sub-maximal exercise (C). METHODS: Eight male physically active subjects (20.8±1.6 years; 74.3±14.9 kg), performed the following tests: 1) 500m and 3km time trial (Vm500 and Vm3km); 2) Incremental test on treadmill for of LL, LV, VO2max and Vmax identification; 3) sustained running at Vmax (Tmax) and identification of the time to VO2max and time at VO2max. The CV and AWC were obtained from linear regression (distance x time on 500m and 3km test). The C was determined as a ratio between sub-maximal running velocity and its VO2. RESULTS: A high correlation was verified for Vm3km and Vmax (r=0.83), Vm3km and VC (r=0.98), Vm500 and VC (r=0.90), Vm500 and Vm3km (r=0.92), and between Vm500 and Time to VO2max (r=0.69). No differences were observed between LL and LV (178.7±20.0 e 180.7±21.8m.min –1) (p>0.05). Also a high correlation between LL and Vmax¬ (r=0.91), CV (r=0.96), and Vm3km (r=0.96) were verified. The AWC was negatively correlated to running economy for those with higher aerobic capacity. CONCLUSION: The CV, AWC, Vm500 an Vm3km can be used for exercise evaluation and training prescription. Due the correlation with the C, the AWC may be an indicative of mechanical inefficiency.Os objetivos do estudo foram analisar as relações existentes entre a velocidade de corrida associada ao VO2max (Vmax), tempo para obtenção do VO2max na Vmax, tempo no VO2max, limiar de lactato (LL), limiar ventilatório (LV), velocidade crítica (VC), capacidade de trabalho anaeróbio (CTAn), desempenho em corrida de 500m e 3km e custo de O2 durante exercício submáximo (C). MÉTODOS: 8 homens fisicamente ativos (20,8±1,6 anos; 74,3±14,9kg) realizaram: 1) Corrida 3km e 500m máximos (Vm3km e Vm500). 2) Teste incremental em esteira para determinação do LL, LV, VO2max e Vmax. 3) Tempo de permanência na Vmax (Tmax), Tempo para atingir o VO2max e Tempo no VO2max. A VC e a CTAn foram obtidas (método linear) a partir dos testes de 3km e 500m. O C foi determinado dividindo-se a velocidade de corrida submáxima pelo respectivo VO2. RESULTADOS: Observou-se alta correlação entre Vm3km e Vmax (r=0,83), Vm3km e VC (r=0,98), Vm500 e VC (r=0,90) e entre Vm500 e Tempo no VO2max (r=0,69). Não foram verificadas diferenças entre LL e LV (178,7±20,0 e 180,7±21,8 m.min-1), sendo o LL altamente correlacionado com Vmax (r=0,91), VC (r=0,96) e Vm3km (r=0,96). Correlação positiva foi observada entre CTAn e C para indivíduos com maior aptidão aeróbia (r=0,79). CONCLUSÕES: As correlações apresentadas entre Vm500 e tempo no VO2max e entre Vm500 e VC indicam que exercícios de curta duração e alta intensidade são positivamente influenciados pela aptidão aeróbia. Devido a correlação significativa com o C, a CTAn se mostra como um possível indicador de ineficiência mecânica no exercício aeróbio