Exercise training improves blood pressure reactivity to stress: a systematic review and meta-analysis

Blood pressure (BP) reactivity to stress is associated with cardiovascular events and the incidence of hypertension, therefore, tolerance to stressors is important for better management of cardiovascular risks. Exercise training is among the strategies that have been investigated as blunting the peak response to stressors, however, its efficacy is poorly explored. The aim was to explore the effects of exercise training (at least four weeks) on BP responses to stressor tasks in adults. A systematic review was performed in five electronic databases (MEDLINE, LILACS, EMBASE, SPORTDiscus, and PsycInfo). Twenty-three studies and one conference abstract was included in the qualitative analysis, totaling 1121 individuals, and k = 17 and 695 individuals in the meta-analysis. Favorable results (random-effects) for exercise training were found, with attenuated peak responses in systolic (standardized mean difference (SMD) = -0.34 [-0.56; -0.11], representing average reductions of 2.5 ± 3.6 mmHg) and null effects on diastolic BP (SMD = -0.20 [-0.54; 0.14], representing average reductions of 2.0 ± 3.5 mmHg). The analysis removing outliers' studies improved the effects for diastolic (SMD = -0.21 [-0.38; -0.05]) but not systolic BP (SMD = -0.33 [-0.53; -0.13]). In conclusion, exercise training seems to lower stress-related BP reactivity, therefore has the potential to improve patients' ability to better respond to stressful situations.

Correlations between health indicators in women who survived breast cancer

The increase in breast cancer survivors (BCS) has established unprecedented demands on health systems worldwide. In this context, new knowledge is needed to subsidize strategies to handle this population. The objective of this study was to combine the correlations between anthropometric, hematological, biochemical, biophysicochemical, muscle strength, and age variables in BCS. Twenty-two volunteers (51.7 ± 9.2 years old) with a history of mastectomy and lymphadenectomy participated in the study. Among the results, the correlations of the body mass index with lipid profile, strength, and body composition draw special attention. The associations of lipid profile with erythrocyte membrane stability, body composition, and leukocyte count, the associations of the red cell distribution width (RDW) with body mass index, lipid profile, and strength, and the positive correlation between age and leukocyte count also deserve highlights. Such findings allow concluding that investigations that deal singly with health indicators represent a severe limitation in the study of the public in question, and it is necessary to avoid them. The complex network of interactions observed between the various parameters studied reinforces the importance of a global biological analysis of attractive cost-benefit and great practical potential. Teams with medical, nutrition, physical therapy, and physical education professionals, among other areas, can use this knowledge to improve BCS's interdisciplinary approaches in short, medium, and long-term management.

Blood Pressure and Heart Rate Variability Responses to High-Intensity Interval Training in Untrained Postmenopausal Women

Purpose: The aim of this study was to analyze the blood pressure (BP) and heart rate variability (HRV) responses in untrained postmenopausal women submitted to acute single sessions of high-intensity interval training (HIT). Method: Sixteen postmenopausal women (59.9 ± 5.6 years, 26.7 ± 3.0 kg/m²) participated in a random order of two acute sessions in a balanced crossover format: control without exercise in sitting position or HIT session. BP and heart rate (HR) were recorded before and during 60 min following the sessions. Results: Diastolic (DBP), mean BP (MBP), and double product (DPO) showed interaction (p < .01). DBP, MBP, and DPO increased (p < .01) after HIT but not after the control session. The area under the curve (AUC) of DBP (p = .02) and DPO (p < .01) were different between conditions. Time and frequency indices of HRV presented interaction (p < .05) which impaired these indices post-HIT, but not post-control. The AUC of time and frequency HRV indices were different between conditions. Conclusions: A single session of HIT may increase BP and cardiac stress and cause perturbation of the autonomic function in untrained postmenopausal women.

Mat Pilates training reduces blood pressure in both well-controlled hypertensive and normotensive postmenopausal women: a controlled clinical trial study

AIM

The aim of this study was to compare the Mat Pilates training-induced responses in resting and ambulatory blood pressure monitoring (ABPM), blood pressure variability (BPV), and heart rate variability (HRV) in well-controlled hypertensive and normotensive postmenopausal women.

METHODS

Forty-seven postmenopausal women were allocated in well-controlled hypertensive (HT) and normotensive (NT) groups. The exercise program was performed three times a week for 12 weeks. Before and after the intervention resting, blood pressure (BP), ABPM, HRV, and BPV were analyzed.

RESULTS

Student's t-test showed no difference in baseline anthropometric and resting BP values between groups. The generalized estimation equation (GEE) showed no interactions (group*time), but time (p < .05) reductions in resting systolic, diastolic and mean BP after training in both groups. Sleep ambulatory systolic, diastolic and mean BP were higher overall in the HT group (p < .05 in group effect). We also found a time effect (p < .05) with significant increases in BPV in the mean diurnal and nocturnal deviations weighted for the duration of the daytime and nighttime interval (SDdn) in systolic, diastolic and mean BP, and in the average real variability (ARV) in diastolic and mean in both groups. In addition, HRV increases (p < .05 in time effect) through the percentage of pairs of adjacent RR intervals with a difference of at least 50 ms (pNN50) after training in both groups.

CONCLUSION

Both normotensive and well-controlled hypertensive postmenopausal women may have similar Mat Pilates exercise training-induced responses in ambulatory BP, BPV and HRV.

Does Obesity Aggravate Climacteric Symptoms in Postmenopausal Women?

OBJECTIVE

 To determine if there is a correlation between body mass index (BMI) and climacteric symptoms in postmenopausal women.

METHODS

 The study sample was composed of 109 postmenopausal women with a mean age of 57 ±  8 years, mean body mass index (BMI) of 30 ±  6 kg/m², and 8 ±  8 years after menopause. For the assessment of the climacteric symptoms, the Blatt-Kupperman Index (BKI), the Menopause Rating Scale (MRS), and the Cervantes Scale (CS) were used. Data analysis was performed through the Chi-squared test, analysis of variance (ANOVA) with the Bonferroni post hoc test, and multiple linear regression. The level of significance adopted was of p < 0.05. The statistical analyses were performed using the Statistical Package for the Social Sciences (IBM SPSS Statistics for Windows, IBM Corp., Armonk, NY, United States) software, version 26.0.

RESULTS

 The multiple linear regression showed a positive association (p < 0.01) between BMI values and menopause symptoms when adjusted for age and time after menopause in the 3 questionnaires used (BKI: B = 0.432; CS: B = 304; and MRS: B = 302). Regarding symptom scores, the obese women had higher mean scores (p < 0.05) when compared to eutrophic women (BKI = 28 ±  10 and 20 ±  10; and MRS = 20 ±  10 and 13 ±  7, respectively). In the Chi-squared analysis, 28% of obese women had severe symptoms and 46% had moderate symptoms, while only 1% and 46% of eutrophic women had these same symptoms.

CONCLUSION

 There is an association between BMI and climacteric symptoms, and overweight or obese women have more intense and moderate symptoms than eutrophic women.

Effects of light-emitting diode therapy on cardiovascular and salivary nitrite responses in postmenopausal women submitted to a single bout of high-intensity interval training

The aim of the present study was to analyze the effects of light-emitting diode therapy (LEDT) on cardiovascular effort during a single bout of high-intensity interval training (HIIT) and on blood pressure (BP), salivary nitrite, and heart rate variability (HRV) responses after the exercise session in postmenopausal women. Sixteen postmenopausal women between 50 and 70 years of age participated in the present study. The intervention comprised two sessions: placebo plus HIIT and LEDT plus HIIT, with a 14-day interval between sessions. The oxygen uptake (VO₂), heart rate (HR), and rating of perceived exertion (RPE) were monitored throughout the HIIT sessions. Salivary samples were taken before, immediately post, and 30' and 60' post-HIIT sessions for nitric oxide (NO) analysis. In addition, HR and BP were checked before, 15 min, 30 min, 45 min, and 60 min post-HIIT sessions. HR data were used to calculate the HRV indices. Cardiovascular parameters during HIIT and BP, HRV, and NO responses were not different between placebo and LEDT conditions (p > 0.05). BP responses increased after compared to pre-exercise (p < 0.01). HRV was impaired post- compared to pre-exercise (p < 0.05). LEDT did not improve physiological performance during HIIT and did not accelerate the recovery of BP and autonomic modulation or change the NO release after exercise in postmenopausal women.

Exercise training and detraining effects on body composition, muscle strength and lipid, inflammatory and oxidative markers in breast cancer survivors under tamoxifen treatment

AIMS

The present study aimed to verify the effects of resistance training (RT) and successive detraining on body composition, muscle strength and lipid profile as primary outcome, and the oxidative stress and inflammatory markers as second outcome of postmenopausal Breast Cancer (BC) survivors undergoing tamoxifen (TA).

MAIN METHODS

Fourteen postmenopausal BC survivors underwent 12 weeks of resistance exercise training and subsequently 12 weeks of detraining. Anthropometric parameters, lipid profile, muscle strength, inflammatory cytokines and the oxidative stress markers, were assessed before, after the training period and after detraining period.

KEY FINDINGS

One-way ANOVA showed that fat mass decrease (39.4 ± 6.9 to 37.7 ± 6.8%) and free-fat mass increase (39.3 ± 4.9 to 40.3 ± 5.6%) after RT. Muscle strength increased in response to training but decreased after the detraining period. Triglycerides (156 ± 45 to 123 ± 43 mg/dL) and total cholesterol (202 ± 13 to 186 ± 16 mg/dL) decreased after the RT and HDL-cholesterol (47 ± 9 to 56 ± 9 mg/dL) increased after RT and remained higher (53 ± 10 mg/dL) than after detraining. IL-6 increases (24.65 ± 10.85 to 41.42 ± 22.88 pg/mL) and IL-17 (2.42 ± 0.32 to 1.69 ± 0.19 pg/mL), TBARS (1.91 ± 0.19 to 1.03 ± 0.1 μmol/L), SOD (24.65 ± 10.85 to 41.42 ± 22.88 U/gHb) and Catalase activity (445.9 ± 113.0 to 345.8 ± 81.7 k/gHb·s) reduced after RT and remained lower after detraining.

SIGNIFICANCE

Resistance exercise training improves health markers of BC survivors undergoing TA and detraining are not sufficient to reverse the positive effects in oxidative stress markers.

Parasympathetic modulation during sleep time is reduced after maximal exercise, correlated with aerobic fitness in young women

abstract It is known that cardiovascular risk is increased during exercise and recovery. Thus, it is necessary to assess all the risk associated with exercise to minimize the possibility of cardiovascular events. The aim of this study was to verify whether a maximal exercise alters ambulatory cardiac autonomic modulation in untrained women and whether aerobic fitness is correlated to cardiac autonomic modulation. Twelve women (25.35 ± 5.44 years) were outfitted with the Holter monitor on an experimental (after maximum exercise) and a control day to heart rate variability (HRV) evaluation. Maximal exercise increased 24 h heart rate (82 ± 14 vs 77 ± 11 bpm; p = 0.04) and during sleep time (72 ± 14 vs. 65 ± 9 bpm; p = 0.01), reduced parasympathetic modulation (HF – n.u. 49.96 ± 11.56 vs 42.10 ± 14.98; p = 0.04), and increased low-frequency/high-frequency ratio (2.88 ± 3.24 vs 1.31 ± 0.60; p = 0.03) during sleep time compared to the control day. Aerobic fitness was correlated positively with LF, HF, and HF (n.u.) indices (r = 0.61 to 0.73, p < 0.05) and correlated negatively with LF (n.u.) and LF/HF ratio (Rho = - 0.57 to - 0.69; p < 0.05). Maximal exercise alters parasympathetic modulation during sleep time in untrained women. Ambulatory cardiac autonomic modulation after exercise is related to aerobic fitness.

Acute and chronic effects of combined exercise on ambulatory blood pressure and its variability in hypertensive postmenopausal women

The aim of this study was to investigate the acute and chronic effects, and their correlation, after combined aerobic and resistance exercises in blood pressure (BP) and its variability (BPV) in hypertensive postmenopausal women. Fourteen hypertensive postmenopausal women monitored BP at rest and during 24 h by ambulatory BP monitoring in a control day without exercise performance a pretraining (baseline), after an acute exercise session (acute), and after a chronic exercise training for 10 weeks (chronic). After exercise training, systolic BP (SBP, Δ = -150 mmHg.24 h), diastolic BP (DBP, Δ = -96 mmHg.24 h), and mean BP (MBP, Δ = -95 mmHg.24 h) area under the curve were smaller than baseline measurements (P < 0.05) with no difference between acute and baseline measurements. The SBP (ΔSD₂₄ = -2, ΔSD_dn = -1.7, and ΔARV₂₄ = -1.9 mmHg), DBP (ΔSD₂₄ = -0.9, ΔSD_dn = -0.8, and ΔARV₂₄ = -0.9 mmHg), and MBP (ΔSD₂₄ = -1.5, ΔSD_dn = -1.3, and ΔARV₂₄ = -1.2 mmHg) variability reduced in acute session in relation to baseline, with no chronic effects. There are moderate correlations between acute and chronic responses in wake SBP, sleep DBP, and SD₂₄. In conclusion, combined exercise reduces ambulatory BP chronically but not acutely. In contrast, BPV decreases after an acute session but not chronically. Awake SBP, sleep DBP, and SD₂₄indices are promising candidates to predict individual cardiovascular responses to exercise.

Isoflavone does not promote additional effects on heart rate variability of postmenopausal women performing combined exercise training: a clinical, controlled, randomized, double-blind study

The aim of the study was to investigate the effects of ingesting isoflavones associated with combined aerobic and resistance exercise training on heart rate variability (HRV) indices in postmenopausal women. Twenty-eight healthy postmenopausal women performed 10 weeks of combined exercise training associated with isoflavone (n = 16) or placebo (n = 12) supplementation. The RR intervals (RRi) were collected for 20 min using a heart rate monitor. Analysis of HRV was performed in time (mean squared difference of successive RRi (RMSSD), standard deviation of all normal RRi (SDNN), and percentage of adjacent RRi differing by more than 50 ms (pNN50)), frequency (low-frequency percentage (LF%), high-frequency percentage (HF%), and low-/high-frequency ratio (LF/HF)), and nonlinear domains (standard deviation of the instantaneous variability of the beat-to-beat interval (SD1), long-term variability of the continuous RRi (SD2), and their ratio (SD2/SD1)). Student's t test did not show differences between groups in any general baseline characteristic variables. The results of the generalized estimating equation tests did not demonstrate interaction or group effects for any HRV indices. However, the results reported time effects for mean RR (p < 0.001), RMSSD (p = 0.044), and SD1 (p = 0.044), with increases in these indices in response to exercise training. There were no time effects for LF%, HF%, LF/HF, SDNN, pNN50, SD2, or SD2/SD1. In conclusion, isoflavone supplementation did not promote additional effects on HRV indices of postmenopausal women subjected to 10 weeks of combined exercise training. Novelty Combined training improves heart rate variability in postmenopausal women. Isoflavone supplementation did not promote additional effects on heart rate variability in postmenopausal women.

Leucine Supplementation Improves Effort Tolerance of Rats With Hyperthyroidism

Leucine is a regulator of protein metabolism in vivo and information on its action on effort tolerance of both animals and humans with hyperthyroidism is scarce. The objective of the present study was to verify the influence of leucine supplementation on the effort tolerance of Wistar rats with experimental hyperthyroidism. 40 animals were divided into four groups of ten: control (C), hormone (H), leucine (L), and hormone + leucine (HL). Hyperthyroidism was induced by daily administration of 20 μ⋅g100 g^-1 of levothyroxine sodium in aqueous suspension by gavage. Leucine was supplemented by adding 5% of the amino acid to the conventional feed. The animals’ blood was collected by cardiac puncture to analyze TSH, T4, and T3 levels. The effort tolerance was determined by the swimming test with a 7% load attached to animals’ tails. Statistical analysis was performed using the Shapiro-Wilk normality test, followed by the analysis of variance (ANOVA) of repeated measures of two factors (treatment × time) and Tukey post hoc, with a significance level of p < 0.05. Administering thyroid hormone increased the swimming performance of rats after 14 and 21 days, but with a drop in performance at 28 days. The HL group, on the other hand, had a significantly higher swimming performance compared to the other groups after 28 days of treatment. Leucine supplementation associated with the experimental model of hyperthyroidism improved the performance of rats in a swimming test after 28 days of treatment.

Eletromyography of abdominal muscles in different physical exercises: An update protocol for systematic review and meta-analysis

BACKGROUND

The abdominal muscles are extremely important because they are directly involved in the functions of support, containment of viscera, and help in the process of expiration, defecation, urination, vomiting, and also at the time of childbirth. Many exercises and equipment are used to strengthen the abdominal muscles, and the workouts are proposed for a variety of purposes, such as preventing and rehabilitating low back pain, improving sports performance, achieving aesthetic standards, among others. Exercises that potentiate the electromyographic activity promote a greater recruitment of muscle fibers and are more effective to improve or maintain of the force. The electromyographic activity analysis allows us to reflect on the quality of the exercises proposed, consequently, to choose and order the exercises properly in a training session.

METHODS

Our systematic review protocol will developed following the reporting items for the systematic review. To identify relevant studies, we sought articles on the following bases: MEDLINE, PubMed, Europubmed, SciELO, Physiotherapy Evidences Data Base (PEDro), Cochrane, and Google Scholar. The methodological quality of the studies included in the review will evaluated using a checklist and quality assessment. For intervention studies, risk of bias will estimated using the Cochrane Collaboration tool.

RESULTS

The results of this study will show the electromyographic activation of the abdomen in the different types of exercises.

CONCLUSION

Ethics approval was not required for this study because it was based on published studies. The results and findings of this study will be submitted and published in a scientific peer-reviewed journal.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018086172.

Effects of aerobic and resistance exercise intensities on 24-hours blood pressure in normotensive women

The present study aimed to determine the effect of the intensity of aerobic and resistance exercise on the 24h BP response in normotensive women. Twenty-four women (aged 33 ± 9 years) performed five experimental sessions in randomized order: CON - no exercise; AE50 - 50% of heart rate reserve (HRR); AE70 - 70% of HRR; RE40 - 40% of 1repetition maximum (RM) and RE70 - 70% of 1RM. Systolic and diastolic BP and HR measurements were measured during 24h post-exercise at the participant's workplace. The AE50, AE70 and RE40 sessions led to the greatest and longest-lasting effects on the SBP, which persisted for up to 24h. For the DBP, the experimental sessions led to similar results; post exercise hypotension was observed until 7h post-exercise, with the exception of the AE70 session, which produced effects that persisted for 24h. Results shows that both aerobic and resistance exercise performed during the morning can decrease the mean BP above the baseline lasting 24 hours during a normal daily work. The aerobic exercise performed around 50% of HRR can better regulate both systolic and diastolic BP in this population.

Type 2 diabetes elicits lower nitric oxide, bradykinin concentration and kallikrein activity together with higher DesArg(9)-BK and reduced post-exercise hypotension compared to non-diabetic condition

This study compared the plasma kallikrein activity (PKA), bradykinin concentration (BK), DesArg(9)-BK production, nitric oxide release (NO) and blood pressure (BP) response after moderate-intensity aerobic exercise performed by individuals with and without type 2 diabetes. Ten subjects with type 2 diabetes (T2D) and 10 without type 2 diabetes (ND) underwent three sessions: 1) maximal incremental test on cycle ergometer to determine lactate threshold (LT); 2) 20-min of constant-load exercise on cycle ergometer, at 90% LT and; 3) control session. BP and oxygen uptake were measured at rest and at 15, 30 and 45 min post-exercise. Venous blood samples were collected at 15 and 45 minutes of the recovery period for further analysis of PKA, BK and DesArg(9)-BK. Nitrite plus nitrate (NOx) was analyzed at 15 minutes post exercise. The ND group presented post-exercise hypotension (PEH) of systolic blood pressure and mean arterial pressure on the 90% LT session but T2D group did not. Plasma NOx increased ~24.4% for ND and ~13.8% for T2D group 15 min after the exercise session. Additionally, only ND individuals showed increases in PKA and BK in response to exercise and only T2D group showed increased DesArg(9)-BK production. It was concluded that T2D individuals presented lower PKA, BK and NOx release as well as higher DesArg(9)-BK production and reduced PEH in relation to ND participants after a single exercise session.

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.

Influence of eNOS gene polymorphism on cardiometabolic parameters in response to physical training in postmenopausal women

The health-promoting effects of exercise training (ET) are related to nitric oxide (NO) production and/or its bioavailability. The objective of this study was to determine whether single nucleotide polymorphism of the endothelial NO synthase (eNOS) gene at positions -786T>C, G894T (Glu298Asp) and at the variable number of tandem repeat (VNTR) Intron 4b/a would interfere with the cardiometabolic responses of postmenopausal women submitted to physical training. Forty-nine postmenopausal women were trained in sessions of 30-40 min, 3 days a week for 8 weeks. Genotypes, oxidative stress status and cardiometabolic parameters were then evaluated in a double-blind design. Both systolic and diastolic blood pressure values were significantly reduced after ET, which was genotype-independent. However, women without eNOS gene polymorphism at position -786T>C (TT genotype) and Intron 4b/a (bb genotype) presented a better reduction of total cholesterol levels (-786T>C: before = 213 ± 12.1, after = 159.8 ± 14.4, Δ = -24.9% and Intron 4b/a: before = 211.8 ± 7.4, after = 180.12 ± 6.4 mg/dL, Δ = -15%), and LDL cholesterol (-786T>C: before = 146.1 ± 13.3, after = 82.8 ± 9.2, Δ = -43.3% and Intron 4b/a: before = 143.2 ± 8, after = 102.7 ± 5.8 mg/dL, Δ = -28.3%) in response to ET compared to those who carried the mutant allele. Superoxide dismutase activity was significantly increased in trained women whereas no changes were observed in malondialdehyde levels. Women without eNOS gene polymorphism at position -786T>C and Intron 4b/a showed a greater reduction of plasma cholesterol levels in response to ET. Furthermore, no genotype influence was observed on arterial blood pressure or oxidative stress status in this population.

Utilização da relação potência-tempo até exaustão em testes de caminhada para avaliação da aptidão aeróbia

O objetivo do presente estudo foi avaliar a aptidão aeróbia em testes de caminhada com carga externa aplicada por meio da inclinação da esteira, a partir da relação não linear entre inclinação da esteira e tempo até a exaustão em velocidade fixa. Doze indivíduos do gênero masculino com 23,2 ± 2,7 anos de idade, 74,0 ± 7,9kg de massa corporal e 23,7 ± 2,5kg·(m²)-1 de IMC, realizaram duas etapas de testes de caminhada em esteira ergométrica com velocidade fixa de 5,5km·h-1 em todos os testes e sobrecarga de intensidade aplicada por meio de inclinação da esteira (%). A etapa 1 consistiu de três testes retangulares até a exaustão voluntária, nas intensidades de 18%, 20% e 22% de inclinação, para determinação dos parâmetros do modelo de potência crítica por dois modelos lineares e um hiperbólico. A etapa 2 consistiu na determinação da intensidade correspondente ao máximo estado estável de lactato sanguíneo (MEEL). ANOVA demonstrou que o modelo hiperbólico (15,4 ± 1,1%) resultou em estimativa significativamente menor que os outros dois modelos lineares inclinação-tempo-1 (16,0 ± 1,0%) e hiperbólico linearizado tempo-1-inclinação (15,9 ± 1,0%), porém, houve alta correlação entre os modelos. Os dois modelos lineares superestimaram a intensidade do MEEL (14,1 ± 1,4%), e o modelo hiperbólico, mesmo sem diferença estatística, apresentou fraca correlação, com baixa concordância em relação ao MEEL. Conclui-se que a relação inclinação-tempo até a exaustão, em testes de caminhada, não permitem a estimativa de intensidade de exercício suportável por longo período de tempo.

Polynomial modeling for the identification of lactate minimum velocity by different methods

AIM

The lactate minimum (LM) protocol has been used to assess aerobic fitness and to predict exercise intensity associated with the maximal blood lactate steady state. The aim of this study was to compare different methods to identify the lactate minimum velocity (LMV) on cycling.

METHODS

Fourteen male cyclists (26.8+/-4.5 years; 173.2+/-6.1 cm; 67.3+/-5.2 kg; 5,8+/-2.9 years of training) performed the LM test in a velodrome. The protocol consisted of an all out 2 km time trial to elevate blood lactate (bLAC), followed by 8 min of recovery and then 6 bouts of 2 km starting 5 kmxh(-1) below the individual mean velocity for the 6 km performance. The velocity was incremented by 1 kmxh(-1) at each bout with 25 microL of capillary blood being collected for bLAC measurements (YSI 2700 STAT). The LMV was identified visually (vLMV), and by applying a second grade polynomial function on 6 (pLMV(6)) and 3 (pLMV(3)) incremental bouts. Additionally, a method where the bLACx work velocity(-1) quotients (LMVQ) were plotted against the correspondent velocity during the incremental test, identified the LMV by considering 6 (LMVQ(6)) or 3 bouts (LMVQ(3)).

RESULTS

ANOVA showed no differences between vLMV (33.1+/-2.5 kmxh(-1)), pLMV(6) (32.9+/-2.5 kmxh(-1)), pLMV(3) (33.2+/-2.3 kmxh(-1)), LMVQ(6) (32.8+/-2.5 kmxh(-1)) and LMVQ(3) (33.4+/-2.3 kmxh(-1)), with high correlation among them.

CONCLUSIONS

It was possible to identify the LMV by the methods proposed in the present study, even when the results of only 3 bouts of the test were modeled by polynomial function. Such an approach enables a more practical and economical test in addition to minimizing the discomfort due to several blood collections.