Double product response is accelerated above the blood lactate threshold

The Effects of Transdermal Nicotine Patches on the Cardiorespiratory and Lactate Responses During Exercise from Light to Moderate Intensity: Implications for Exercise Prescription during Smoking Cessation

Background and objectives: Exercise can help ease withdrawal symptoms of smokers. However, there is little information about the physiological responses, such as cardiorespiratory and lactate (La) responses, during exercise from light to moderate intensity combined with transdermal nicotine patches (TNPs) in smokers. This study aimed to investigate the effect of TNPs on the cardiorespiratory and La responses during exercise at light to moderate intensity. Materials and Methods: Fourteen young men (8 non-smokers, 6 current smokers) aged 20 to 26 years participated in this study. They performed an incremental graded submaximal exercise test using an electromagnetic cycle ergometer set from 30 to 210 W with (TNP condition) or without a TNP (control condition) in a random order. The TNP was applied to the left arm 8–10 h prior to starting the exercise to achieve the peak level of blood nicotine concentration. Heart rate (HR), rate of perceived exertion (RPE), oxygen consumption (VO₂), ventilation (VE), and blood La at rest and during exercise were measured and analyzed. Results: The HR at rest was significantly higher in the TNP condition than in the control condition (TNP; 74.7 ± 13.8 bpm, control; 65.3 ± 10.8 bpm, p < 0.001). There was no interaction (condition × exercise intensity) between any of the variables, and VO₂, VE, RPE, and La during exercise were not significantly different between the conditions. However, HR during exercise was 6.7 bpm higher on average in the TNP condition. Conclusions: The HR during exercise was greater at light to moderate intensity with a TNP. Our study results will guide clinicians or health professionals when prescribing exercise programs combined with TNPs for healthy young smokers.

Individual variations in steps per day for meeting physical activity guidelines in young adult women

Cross-sectional studies have found a correlation between the duration or volume of moderate-to-vigorous physical activity (MVPA) and steps per day (STEP), but there is little information on why this relationship varies among individuals. No previous research has established whether STEP can be used to estimate the duration of physical activity (PA) at or above lactate threshold (≥LT), such as for maintaining cardiorespiratory fitness. This study explored the association among STEP, MVPA indices, and ≥LT under free-living conditions. Seventy young adult women measured their PA for 7 days using a validated accelerometer. The mean LT measured by an exercise test was 5.8 ± 1.0 METs. STEP, MVPA, METs×h, and ≥LT were 9324 ± 2677 steps/day, 231.9 ± 101.5 min/week, 16.6 ± 7.4 METs×h/week and 24.0 ± 22.2 min/week, respectively. Significant correlations were found between STEP and MVPA duration and between STEP and METs×h/week (r = 0.81 and r = 0.81); however, approximately 1600 steps/day of the standard error of estimates in the regression equations were found. Multiple stepwise regression analysis revealed that the percentage of total time spent at light-intensity PA (LPA) and MVPA were significant determinants of the percent deviation of STEP from the linear relationships between STEP and MVPA indices. No significant relationship was observed between ≥LT and STEP. The association between STEP and MVPA fluctuated depending on individual daily LPA and MVPA. Thus, consideration of both STEP and the PA at specific intensities are necessary to ensure the PA guidelines are met and the health benefits gained. STEP alone would be not a sufficient indicator for assessing the ≥LT.

Association between exercise intensity and renal blood flow evaluated using ultrasound echo

BACKGROUND

High-intensity exercise reduces renal blood flow (RBF) and may transiently exacerbate renal dysfunction. RBF has previously been measured invasively by administration of an indicator material; however, non-invasive measurement is now possible with technological innovations. This study examined variations in RBF at different exercise intensities using ultrasound echo.

METHODS

Eight healthy men with normal renal function (eGFR_cys 114 ± 19 mL/min/1.73 m²) participated in this study. Using a bicycle ergometer, participants underwent an incremental exercise test using a ramp protocol (20 W/min) until exhaustion in Study 1 and the lactate acid breaking point (LaBP) was calculated. Participants underwent a multi-stage test at exercise intensities of 60, 80, 100, 120, and 140% LaBP in Study 2. RBF was measured by ultrasound echo at rest and 5 min after exercise in Study 1 and at rest and immediately after each exercise in Study 2. To determine the mechanisms behind RBF decline, a catheter was placed into the antecubital vein to study vasoconstriction dynamics.

RESULTS

RBF after maximum exercise decreased by 51% in Study 1. In Study 2, RBF showed no significant decrease until 80% LaBP, and showed a significant decrease (31%) at 100% LaBP compared with at rest (p < 0.01). The sympathetic nervous system may be involved in this reduction in RBF.

CONCLUSIONS

RBF showed no significant decrease until 80% LaBP, and decreased with an increase in blood lactate. Reduction in RBF with exercise above the intensity at LaBP was due to decreased cross-sectional area rather than time-averaged flow velocity.

An integrative perspective of the anaerobic threshold

The concept of anaerobic threshold (AT) was introduced during the nineteen sixties. Since then, several methods to identify the anaerobic threshold (AT) have been studied and suggested as novel 'thresholds' based upon the variable used for its detection (i.e. lactate threshold, ventilatory threshold, glucose threshold). These different techniques have brought some confusion about how we should name this parameter, for instance, anaerobic threshold or the physiological measure used (i.e. lactate, ventilation). On the other hand, the modernization of scientific methods and apparatus to detect AT, as well as the body of literature formed in the past decades, could provide a more cohesive understanding over the AT and the multiple physiological systems involved. Thus, the purpose of this review was to provide an integrative perspective of the methods to determine AT.

Double product break point estimates ventilatory threshold in individuals with type 2 diabetes

[Purpose] To verify the identification of the anaerobic threshold through the double product breakpoint (DPBP) method for individuals with type 2 diabetes. [Subjects and Methods] Nine individuals with T2D (7 females; age=63.2 ± 8.9 y) and 10 non-diabetic (ND) (7 females; age=58.3 ± 7.8 y) performed an incremental exercise test on a cycle ergometer. Heart rate (HR), blood pressure (BP) and expired gas were measured at the end of each stage. The ventilatory threshold (VT) and DPBP were considered as the exercise intensities above which an over proportional increases in VE and DP were observed in relation to increasing workload. [Results] No differences were observed between the workloads, HR and VO2 corresponding to the AT identified respectively by VT and DPBP. For the T2D, strong correlations between VT and DBPB workloads (r=0.853), HR (r=0.714), and VO2 (r=0.863) were found. These relationships were similar to those found for the control group (r=0.923; r=0.881; and r=0.863, respectively). [Conclusion] These results demonstrate that the DPBP enables for the prediction of AT and correlated well the VT in both the T2D and ND participants.

Anaerobic Threshold and Salivary α-amylase during Incremental Exercise

[Purpose] The purpose of this study was to clarify the validity of salivary α-amylase as a method of quickly estimating anaerobic threshold and to establish the relationship between salivary α-amylase and double-product breakpoint in order to create a way to adjust exercise intensity to a safe and effective range. [Subjects and Methods] Eleven healthy young adults performed an incremental exercise test using a cycle ergometer. During the incremental exercise test, oxygen consumption, carbon dioxide production, and ventilatory equivalent were measured using a breath-by-breath gas analyzer. Systolic blood pressure and heart rate were measured to calculate the double product, from which double-product breakpoint was determined. Salivary α-amylase was measured to calculate the salivary threshold. [Results] One-way ANOVA revealed no significant differences among workloads at the anaerobic threshold, double-product breakpoint, and salivary threshold. Significant correlations were found between anaerobic threshold and salivary threshold and between anaerobic threshold and double-product breakpoint. [Conclusion] As a method for estimating anaerobic threshold, salivary threshold was as good as or better than determination of double-product breakpoint because the correlation between anaerobic threshold and salivary threshold was higher than the correlation between anaerobic threshold and double-product breakpoint. Therefore, salivary threshold is a useful index of anaerobic threshold during an incremental workload.

Effects of leg blood flow restriction during walking on cardiovascular function

INTRODUCTION

Exercise with limb blood flow restriction (BFR) is a very popular exercise modality in Japan and is spreading widely to the rest of the world. The underlying principle of this training modality is that under the conditions of restricted blood flow, even low-intensity exercise can provide significant muscle strength and hypertrophy. One concern, however, is that BFR during exercise may place unnecessary burden on those with compromised cardiac function.

METHODS

We determined the impact of leg BFR during walking on cardiovascular function in 17 young (26 ± 1 yr) healthy volunteers. Each subject underwent five bouts of 2-min treadmill walking at 2 miles·h(-1) with 1-min interval either with or without tourniquet cuffs inflated on both thighs.

RESULTS

Heart rate increased more during the BFR session, whereas stroke volume decreased greater during the BFR session. Blood pressure increased significantly and substantially during the BFR session. Consequently, an increase in double product, an index of myocardial oxygen demand, was more than threefold higher in the BFR condition. Systemic arterial compliance evaluated by stroke volume/pulse pressure ratio significantly increased during the control session by 14% but reduced during the BFR condition by 19%. Popliteal artery flow-mediated vasodilation decreased significantly after the exercise with BFR but not after the control session.

CONCLUSIONS

Even at low intensity, the aerobic exercise with BFR requires a greater cardiac work and decreases endothelial function. Limb BFR during exercise may need to be more cautiously prescribed to those with compromised cardiac conditions.

Relationships between fat deposition in the liver and skeletal muscle and insulin sensitivity in Japanese individuals: a pilot study

PURPOSE

To evaluate the relationships between insulin sensitivity (IS), body fat accumulation, and aerobic capacity in middle- to older-aged Japanese participants with visceral adiposity.

PARTICIPANTS AND METHODS

Aerobic capacity was measured during an incremental ramp exercise test. Computed tomography was used to measure visceral (VFA) and subcutaneous (SFA) fat area, the fat in liver-to-spleen ratio (L/S), and low-density skeletal muscle area (LDMA). IS was assessed using euglycemic-hyperinsulinemic clamps.

RESULTS

A total of 11 males and 9 females, age 58 ± 9 years (mean ± standard deviation), body mass index 29 ±4.1 kg/m(2), and VFA 190 ±53 cm(2) participated in this study. In unadjusted models, VFA, LDMA, and L/S were significantly correlated with IS, which remained in adjusted models for LDMA and L/S, but not for VFA. In multiple stepwise regression analysis including sex, age, body fat, VFA, SFA, alcohol consumption, and aerobic capacity (oxygen uptake at the lactate threshold), L/S, and LDMA accounted for 70% of the total variance in IS. Percentage body fat and SFA, but not VFA, were significantly correlated with high molecular-weight adiponectin levels (r = 0.58, P < 0.01 and r = 0.54, P < 0.05, respectively). IS and L/S were significantly and negatively correlated with tumor necrosis factor-α (r = -0.67 and -0.63, respectively; both P < 0.01) and plasminogen activator inhibitor-1 (r = -0.58, P < 0.01 and -0.52, P < 0.05, respectively), whereas LDMA was not.

CONCLUSION

These findings indicate that ectopic fat deposition in the liver and skeletal muscle may be associated with peripheral IS independently of body fat accumulation and aerobic capacity in middle- to older-aged Japanese individuals with visceral adiposity. Because of the small sample size, additional larger studies are needed to provide further insight into these preliminary findings.

The influence of aerobic exercise training on the double product break point in low-to-moderate risk adults

The double product is the product of the heart rate and systolic blood pressure. The double product break point (DPBP) is a physiologic threshold that occurs at similar exercise intensities to that of the ventilatory threshold (VT). The influence of aerobic exercise training on the DPBP has not yet been examined. The purpose of this study was to examine whether aerobic exercise training (ET) increases the exercise intensity at which the DPBP occurs, and whether it increases in a similar fashion to the VT. Seven males and 11 females, all sedentary (mean ± SD: age = 29.9 ± 10.5 years) underwent supervised cardiopulmonary exercise testing using a cycle ergometer ramp protocol at baseline and after 8 weeks of vigorous ET on a cycle ergometer. The VT was determined by gas analysis and the V-slope method. Experienced observers using standardized instructions visually determined the DPBP. Following ET, VO(2 peak), maximal workload, and body composition variables all showed significant positive changes. The VO(2) at which the DPBP and VT occurred increased significantly from baseline to follow-up (P < 0.001). At baseline and at follow-up, the DPBP and VT did not differ. The DPBP and VT were significantly correlated to each other at both time points. Results suggest that the DPBP responds to ET in a similar fashion to that of the VT, and may be an easier and more useful marker of the VT for exercise training purposes.

Improved cardio-respiratory fitness correlates with changes in the number and size of small dense LDL: randomized controlled trial with exercise training and dietary instruction

OBJECTIVE

To investigate the correlation between lifestyle improvements, in particular increased cardio-respiratory fitness and changes in the blood lipid profile.

METHODS

The participants were 217 residents of Fuji and Yamato Towns, Saga City, with mildly abnormal blood pressure, serum lipids or blood glucose detected at health check-ups in 2003. Participants were randomly allocated to an Intervention (108 subjects) or Control group (109 subjects), matched for age and various conditions. The Intervention group was given exercise advice and prescription and dietary instructions. Cardio-respiratory fitness was evaluated using the work rate at double product breaking point. Changes of lipid parameters were compared before and after intervention, and examined the relationship with cardio-respiratory fitness.

RESULTS

Seventy nine subjects in each group could be followed up for 17 months without requiring pharmacotherapy. Body mass index, waist circumference, systolic blood pressure, homeostasis model assessment insulin resistance, and triglycerides were decreased in the Intervention group. Furthermore, apolipoprotein B levels were lower (p<0.05), and the ratio of LDL cholesterol to apolipoprotein B (LDL/ApoB) was higher (p<0.001). When all subjects were divided into 3 subgroups according to the degree of improvement in cardio-respiratory fitness, LDL/ApoB increased and apolipoprotein B decreased as the degree of improvement increased (p<0.05).

CONCLUSION

Improvement was seen in atherosclerotic risk factors through lifestyle modification. In particular, improved cardiorespiratory fitness was associated with qualitative and quantitative changes in LDLs.

Influence of adiponectin gene polymorphism SNP276 (G/T) on adiponectin in response to exercise training

Adiponectin is an adipocytokine that is involved in insulin sensitivity. The adiponectin gene contains a single nucleotide polymorphism (SNP) at position 276 (G/T). The GG genotype of SNP276 (G/T) is associated with lower plasma adiponectin levels and a higher insulin resistance index. Therefore, we examined the influence of SNP276 (G/T) on the plasma level of adiponectin in response to exercise training. Thirty healthy Japanese (M12/F18; 56 to 79 years old) performed both resistance and endurance training, 5 times a week for 6 months. The work rate per kg of weight at double-product break-point (DPBP) was measured. Blood samples were obtained before and after the experiment. Plasma concentrations of adiponectin, HbA1c, insulin, glucose, total, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) cholesterol, and triglyceride were measured. Genotypes of SNP276 were specified. Student's t-test for paired values and unpaired values was used. After the 6-month training period, the work rate per kg of weight at DPBP and the plasma HDL-cholesterol level were significantly improved (P<0.05), while no change was observed in the total plasma adiponectin level. However, the plasma adiponectin level in those with the GT + TT genotype had significantly increased (P<0.05). Additionally, the degree of the decrease in the HOMA-R level was significantly greater in the subjects with the GT + TT genotype than those with the GG genotype (p<0.05). Our results suggest that subjects with the genotype GT + TT at SNP276 (G/T) have a greater adiponectin-related response to exercise training than those with the GG genotype.

Age-related reduction of systemic arterial compliance relates to decreased aerobic capacity during sub-maximal exercise

A decrease in systemic arterial compliance (SAC) increases left ventricular load along with the demand for excessive myocardial oxygen consumption when the age-related reduction of SAC reaches a marked level, and consequently may depress left ventricular pump function. Reduced left ventricular pump function decreases aerobic capacity, and some study groups have shown that SAC and/or central arterial distensibility is correlated with maximal aerobic capacity in humans. We thus hypothesize that, once the age-related reduction of SAC reaches a marked level, the participation of SAC in aerobic capacity will be significant even during sub-maximal exercise. Thirty young humans and 46 elderly humans participated in this study. SAC, oxygen uptake at the ventilatory threshold (VO2VT), and the ratio of increase in oxygen uptake, in cardiac output, and in effective arterial elastance to increase in work rate (deltaVO2/deltaWR, deltaCO/deltaWR and deltaEa/deltaWR) were measured. SAC was significantly higher in young subjects compared with elderly subjects, and was significantly related to VO2VT in elderly subjects. SAC also significantly correlated with deltaVO2/deltaWR, deltaCO/deltaWR and deltaEa/deltaWR in elderly subjects. When total subjects were divided by the value of SAC into 6 groups, the VO2VT values in the 3 groups with lower SAC were significantly lower than those in the 3 groups with higher SAC, and gradually decreased with the reduction of SAC. There were no changes in VO2VT among the 3 groups with higher SAC. These results suggest that the participation of SAC in aerobic capacity is significant even during sub-maximal exercise in individuals who show a pronounced age-related reduction of SAC.

Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations

A model for systematic changes in patterns of inter-individual variation in affective responses to physical activity of varying intensities is presented, as a conceptual alternative to the search for a global dose-response curve. It is theorized that trends towards universality will emerge in response to activities that are either generally adaptive, such as moderate walking, or generally maladaptive, such as strenuous running that requires anaerobic metabolism and precludes the maintenance of a physiological steady state. At the former intensity the dominant response will be pleasure, whereas at the latter intensity the dominant response will be displeasure. In contrast, affective responses will be highly variable, involving pleasure or displeasure, when the intensity of physical activity approximates the transition from aerobic to anaerobic metabolism, since activity performed at this intensity entails a trade-off between benefits and risks. Preliminary evidence in support of this model is presented, based on a reanalysis of data from a series of studies.

Practical markers of the transition from aerobic to anaerobic metabolism during exercise: rationale and a case for affect-based exercise prescription

BACKGROUND

The high rates of dropout from exercise programs may be attributed in part to the poor ability of most individuals to accurately self-monitor and self-regulate their exercise intensity. The point of transition from aerobic to anaerobic metabolism may be an appropriate level of exercise training intensity as it appears to be effective and safe for a variety of populations. Possible practical markers of this event were compared.

METHODS

Two samples of 30 young and healthy volunteers each participated in incremental treadmill tests until volitional exhaustion. The ventilatory threshold, a noninvasive estimate of the aerobic-anaerobic transition, was identified from gas exchange data. Heart rate, self-ratings of affective valence (pleasure-displeasure), perceived activation, and perceived exertion were recorded every minute.

RESULTS

In both samples, heart rate, perceived activation, and perceived exertion rose continuously, whereas the ratings of affective valence showed a pattern of quadratic decline, initiated once the ventilatory threshold was exceeded.

CONCLUSIONS

Exercise intensity that exceeds the point of transition from aerobic to anaerobic metabolism is accompanied by a quadratic decline in affective valence. This marker may be useful in aiding exercisers to recognize the transition to anaerobic metabolism and, thus, more effectively self-monitor and self-regulate the intensity of their efforts.

Change in double product during stepwise incremental exercise

The purpose of this study was to observe the change in double product with increases in the intensity of bicycle exercise. Eleven young male adults participated in this study. The subjects performed graded bicycling exercise increasing 20 watts every 2 min from 0 watts until the heart rate (HR) reached 170 beats.min(-1). During exercise systolic blood pressure (SBP) and HR were continuously measured. Initially SBP gradually increased with the increase in workload, but when the intensity of exercise became even higher, the rate of increase slowed. On the other hand, the increase in HR was very small during the initial 5 min of exercise and when the intensity of exercise increased, the rate of increase of HR became higher. The polygonal regression analyses on the relation of double product to elapsed time revealed clear break-points. On average, the break-point of double product was 6.6 min (56 watts). These results clearly showed that the break-point of double product with an increase in workload appeared even though the workload was relatively low.

Influence of mild exercise at the lactate threshold on glucose effectiveness

The effect of a single bout of mild exercise on glucose effectiveness (S(G)) and insulin sensitivity (S(I)) was studied in six young male subjects by using a minimal model. An intravenous glucose tolerance test was performed under two conditions as follows: 1) 25 min after a bout of exercise on a cycle ergometer at the lactate threshold level for 60 min (Ex) and 2) without any prior exercise (Con). Leg blood flow (LBF) was also measured by strain-gauge plethysmography simultaneously with blood sampling. S(I) did not significantly change after exercise (18.1 +/- 1.5 vs. 17.7 +/- 1.9 x 10-(5) min/pM), whereas S(G) significantly increased (0.016 +/- 0.002 vs. 0.025 +/- 0.002 min(-1), P < 0.01). The increased blood flow after exercise remained high during the time period for measurement of the glucose disappearance constant and may be a determinant of S(G). The incremental lactate area under the curve until insulin loading was also significantly higher in Ex than in Con (2.6 +/- 0.9 vs. -3.5 +/- 1.5 mM/min, P < 0.05). These results suggest that increased S(G) after mild exercise may be due, at least in part, to increased LBF and lactate production under a hyperglycemic state.

Identification of the anaerobic threshold using double product in patients with coronary artery disease

This study compared the ventilatory threshold with the double-product break point in 104 patients with cardiovascular disease during ramp treadmill testing. The high correlation (r = 0.81) between the double-product break point and the ventilatory threshold, even in patients taking beta blockers, suggests the former method is a viable noninvasive alternative for identifying the anaerobic threshold in patients with cardiovascular disease, particularly when expired gas analysis is not appropriate or available.