Moderate/high resistance exercise is better to reduce blood glucose and blood pressure in middle-aged diabetic subjects

There are different types of diabetes, but type 2 diabetes mellitus (T2D) is the most common, affecting 95% of subjects with diabetes worldwide1. T2D main characteristic is insulin resistance and presents two clinical outcomes: hyperglycemia and hyperinsulinemia2. Diabetes can lead to different types of comorbidities such as hypertension. At least 70% of individuals with T2D have uncontrolled hypertension or have been treated for elevated blood pressure (BP)3. The maintenance of BP within the normal level is important in order to not only promote greater and better control of hypertension but also of the blood glucose levels and physical exercise is an essential tool to make it happen4. The absence or low practice of physical exercise, as well as a sedentary lifestyle, can contribute to the development of T2D and hypertension2,5. Physical exercise can induce post-exercise hypotension (PEH) and reduce glycemic level, especially during the first 24h6,7. Thus, aerobic exercise is usually recommended in T2D and hypertension, but resistance exercise (RE) can also induce physiological benefits6. RE movements are interspaced, and the muscle contraction is executed by a particular muscle Abstract


Introduction
Moderate/high resistance exercise is better to reduce blood glucose and blood pressure in middle-aged diabetic subjects There are different types of diabetes, but type 2 diabetes mellitus (T2D) is the most common, affecting 95% of subjects with diabetes worldwide 1 . T2D main characteristic is insulin resistance and presents two clinical outcomes: hyperglycemia and hyperinsulinemia 2 . Diabetes can lead to different types of comorbidities such as hypertension. At least 70% of individuals with T2D have uncontrolled hypertension or have been treated for elevated blood pressure (BP) 3 . The maintenance of BP within the normal level is important in order to not only promote greater and better control of hypertension but also of the blood glucose levels and physical exercise is an essential tool to make it happen 4 . The absence or low practice of physical exercise, as well as a sedentary lifestyle, can contribute to the development of T2D and hypertension 2,5 .
Physical exercise can induce post-exercise hypotension (PEH) and reduce glycemic level, especially during the first 24h 6,7 . Thus, aerobic exercise is usually recommended in T2D and hypertension, but resistance exercise (RE) can also induce physiological benefits 6 . RE movements are interspaced, and the muscle contraction is executed by a particular muscle Abstract Type 2 diabetes (T2D) main feature is insulin resistance. Hypertension is a comorbidity linked to T2D. Resistance exercise (RE) is an important non-pharmacological tool to contribute to managing blood glucose and blood pressure (BP), but there is not a common sense about acute effects. The aim of this study was to evaluate the acute physiological effects after two different RE sessions using different intensities at middle-aged hypertensive T2D subjects. There were 40 middle-aged men (20 nondiabetics; 20 diabetics), who underwent an exercise protocol with the same volume at 60% or 75% of the one maximum repetition test (1RM), consisting in: bench press, triceps pulley, rowing machine, barbell curl, lateral raise with dumbbells and barbell squat. Physiological changes were evaluated through BP, glycemia, creatine kinase, lactate dehydrogenase, C reactive protein (C-RP), testosterone and cortisol. For non-diabetics, both intensities promoted blood glucose uptake (8.2% to 11.1%, p<0.05), and only the 75%1RM session induced blood glucose uptake in 5.7% in the diabetics. Post-exercise hypotension was significant after RE at 75%1RM for systolic BP (SBP) and after both intensities for diastolic BP (DBP) in non-diabetics, while the SBP and DPB reduced after both intensities for diabetics. RE at 75%1RM resulted in better blood glucose uptake, and both intensities reduced the BP in diabetic subjects. After 75%1RM there was a higher indirect muscle damage result. The alterations in hormones, C-RP, and indirect muscle damage markers indicated an adequate acute anabolic recovery with no significant inflammation in both intensities. Acute RE at 60%1RM or 75%1RM can used as an extra tool to manage both pathologic conditions. Keywords: Type 2 Diabetes Mellitus; Hypertension; Resistance Exercise; Health. or a muscle group which is opposed to a force, and sometimes, is against to the movement 6,8 .
Physiological alterations are observed in RE such as muscle damage and hormonal changes immediately after RE. Creatine kinase (CK) and lactate dehydrogenase (LDH) increase are wellknown indirect muscle damage markers and are important tools to define the effectiveness of the physical training. The high concentration differences in pre and post-workout for CK and LDH are the basis of muscle damage and C reactive protein (C-RP) can be used as a complementary marker to determine if the damage is harmless or not 9 .
Hormonal changes are also part of the physiological changes during and immediately after RE sessions. Testosterone levels are usually reduced in T2D. Changes in testosterone levels can influence insulin sensitivity, amplifying or not the glucose uptake and its transport to different tissues 10 . Alterations in the levels of cortisol can induce modifications in the recruitment of different types of muscular fibers during RE and may contribute to loss of muscle mass (sarcopenia), and to the reduction of muscular strength (dynapenia) 11 . Positive change in the testosterone and cortisol ratio (T:C) indicates a good physiological recovery and represents the relation between anabolic and catabolic systems.
Low T:C ratio may indicate the beginning of the development of insulin resistance, obesity, and cardiovascular dysfunction 10 .
It has been shown 12 that the blood glucose control obtained with the use of chronic highintense RE is more effective in controlling glycemia levels than the moderate and light RE. However, moderate exercise intensity, in a chronic model, is more indicated for safety reasons 13 to groups with a history of diabetes and hypertension, as recommended by American College of Sports Medicine and American Heart Association 14 .
The moderate RE is performed at any intensity between 60% and 80% of the maximum weight workload carried out by an individual 15 , however, it is not clear in which percentage of the maximum intensity, lower or higher, the moderate RE would provide a better acute physiological response when performed by hypertensive T2D individuals. The confirmation of changes in physiological results after different moderate intensities of RE to this population can lead to advances in the prescription and evaluation of physical exercise training.
The aim of this study was to evaluate the acute effects of two different moderate RE intensities on the glycemia, blood pressure and markers of stress and muscle damage at middle-aged hypertensive type 2 diabetic subjects.
The National Committee for Ethics in Research and the Ethics Committee of the Federal University of Sergipe approved this study under protocol 387.704. All participants signed a consent form authorizing the participation and the use of the data collected in this study, according to Resolution 466/12 of the National Health Council of Brazil and followed the Declaration of Helsinki.

Subjects
The sample was composed of 40 male volunteers. There were initially two groups: nondiabetics (ND; control group) and hypertensive diabetics (D), who were later subdivided into 4 groups, consisting of 10 individuals each, separated according to the percentage of the maximum intensity session. The groups performed the RE protocols at 60% (ND60 and D60) or at 75% (ND75, and D75) of the 1 repetition maximum test (1RM). The main features of the groups are shown in TABLE 1. These intensities are moderate and they were chosen due safety reasons, being 60% of 1RM closer to lowest moderate exercise zone, and 75% of 1RM is still moderate zone, closer to 80% of 1RM, considered the threshold zone between moderate and intense zone 16 .
The including criteria adopted to participate in the exercise protocol was: to be a male between 40 and 60 years old, and could not be doing regular physical activity during the last six months was a must. It was not considered regular Method physical activity if the exercise or sport was performed less than 3 times a week in a shorter period than 30 minutes 13 . Diabetic hypertensive volunteers included in the study had the disease diagnosed clinically by a physician for at least one year and the glucose levels and blood pressure controlled by diet and/or medication. It would be excluded from the study anyone who was making use of exogenous insulin, or if they had chronic complications such as cardiovascular disease (excluding hypertension), diabetic foot, retinopathy, neuropathy, and nephropathy 6 .
An individualized breakfast was suggested to all participants of the experimental protocol. This procedure was adopted because a rich breakfast in fats or carbohydrates may influence the blood glucose level at pre-and post-exercise protocol. Water was freely consumed before and after the procedure. All procedures were conducted by the same professional at all times.

Exercise Sessions
One week prior to the 1RM, there was a habituation session where the participants had contact with the exercises they would perform and execute them without weights. The 1RM test was performed to establish the weight load of two moderate RE intensities used during exercise sessions. 1RM consisted of one single repetition using the maximum of the weight load that can lifted during the execution of a specific exercise. It was performed with alternation between the concentric and eccentric phases taking 2s for each phase 17 . After the first trial, participants had a passive interval of 180s. When the execution of the movement was successful, 10% of the work load used was added, and in case of failure, 10% was removed by the weight used. A maximum of 3 attempts, increasing or decreasing the load, was established to determine the maximal strength.
Each group performed a single session of the exercise protocol. After the resting period, stretches were performed for 5 minutes to the upper limb. Right after the stretching period, the subjects performed a warm-up for the main muscle groups of their body (chest, back, and legs) using two series with the minimum weight on the machines and barbells, executing 20 repetitions of specific exercises for these muscle groups (described in the experimental protocol below). The interval between sets was 45 seconds.
Five minutes after the warm-up the test protocol was initiated.
The experimental protocol was performed 72 hours after the 1RM test for each group. All subjects performed the RE session just once and the four groups executed the same exercise sequence, with intensities at 75% or 60% of 1RM. All sessions were performed consisting of 3 sets of 10 repetitions each. The resting time between sets was 1 minute 13 and the rate of contraction of the exercise was 2s for the concentric phase and 2s for the eccentric 18 .
Exercises used for all groups were an attempt to portray a traditional session for beginners at gyms, consisting of 6 exercises and working out the main muscular groups. The exercises chosen to be performed were: bench press, triceps pulley, rowing machine, barbell curl, lateral raise with dumbbells and barbell squat, and always in the same order for all participants. It is important to highlight that the 1RM was performed in each of these six exercises. The total volume was calculated to each intensity of RE from the sum the results of the multiplication of the load of each exercise by repetitions and series.

Pre-and post-exercise procedures
Blood pressure and heart rate were measured before and 1h after the exercise session by an oscillometric tensiometer (branch Omron, automatic arm equipment, Hem 7200 model). The BP was measured on the left arm of the participants that were keeping in a seated position.
Blood capillary samples from fingers were collected and placed in tapes to evaluate glycemia (Acku-Check Advantage), as well as blood samples, were collected by antecubital vein for 4 ml per tube from each subject. Blood samples collections occurred between 7:00 and 9:00 am, before experimental protocols and 10 minutes after exercise sessions to analyze glycemia, as well as, CK, LDH, C-RP, testosterone, and cortisol.
When the systolic and/or diastolic blood pressure and/or glycemia presented values ≥ 180 mmHg and/or 105 mmHg 19 and/or ≤100mg/ dL or ≥300mg/dL 20 , the experimental session was rescheduled, and the volunteer was aimed at finding a basic health unit. These situations did not occur.
CK and LDH were measured in the plasma, through the kinetic colorimetric method at Results multiple time points 9 . The method used to dosage of the C-RP was the high sensitivity turbidimetry 21 . C-RP analysis was performed in an automatic spectrophotometer and when "positive", it was considered as an inflammatory zone. Testosterone and cortisol analyses were performed through chemiluminescence method. Blood samples were centrifuged for 10 min at 3000 rpm and an automatic biochemical analyzer was used. Bio Advance Kits were used during the dosages. The T: C ratio was obtained by dividing the testosterone concentrations by cortisol concentrations.
Disposable syringes and materials were used in all samples collected by the same professional at all times. One Huma Star 300 spectrophotometer, Human brand, was used for biochemical analyses. A centrifugal of the CELM brand model was also used.

Statistical Analyses
Mean and standard deviation (SD) were used for statistical analysis. Normality of the data was evaluated through Shapiro-Wilk test. Analysis of variance (ANOVA) for repeated measures between the four groups and two moments (with a syntax of 4x2) with multiple's pairs comparisons of Bonferroni was applied for glycemia, BP, testosterone, cortisol, CK, and LDH. The significance level was set at 5% (p<0.05), and all analysis were carried out using the SPSS 15.0 version. 60% and 75% 1RM for nondiabetic groups (8.2% and 11.1%, respectively), however only RE at 75% 1RM resulted in significant reduction of 5.7% on glycemia level in the diabetic group (FIGURE 1A).
After exercise protocols, significant reductions (p≤0.05) were observed for SBP to ND75, D60, and D75 (FIGURE 1B), and for DBP to ND and D groups (FIGURE 1C). The RE at 75% 1RM revealed a better reduction for SBP and DBP for ND and D groups, especially for ND group (p<0.05). TABLE 1 shown the rest values for different variables in the present study, divided between nondiabetic (ND) and diabetic (D) groups in each RE intensity. Only heart rate, testosterone, cortisol, CK and LDH levels did not differ between groups. All three sets were completed for all volunteers in all attempts.
Glycemia was reduced (p<0.05) after RE at In relation to hormonal variables, there was significant elevation (p<0.05) of the testosterone for ND75, but not for ND60, however, both RE sessions resulted in increasing of the testosterone (p<0.05) for D groups (FIGURE 2A). There was a reduction (p<0.05) of the cortisol, but not to D60 (FIGURE 2B). The ratio T:C post-RE was higher than pre-RE for both groups and intensities, except for ND60.
CK and LDH presented significant changes in different moments and groups but is relevant to highlight the significant increase (p<0.05) for those variables after RE at 75%1RM, (FIGURES 3A and B).  The main finding in this study was the fact of highest moderate intensity (75%1RM) showed a better glucose uptake from the diabetic group. In addition, independently of RE intensity, the moderate exercises sessions were capable to reduce BP of diabetic groups with a notable tendency to a better reduction in the higher RE intensity. The hormonal response after exercises was suitable for a good exercise recovery, mainly for exercise performed at 75%1RM, which resulted in an elevated indirect marker of muscle damage.
In the present study, the diabetics presented higher BMI, glycemia, SBP, and DPB than nondiabetic groups. Normally, diabetic individuals present many physiological dysfunctions such as cardiovascular disease and hypertension, what increase morbidity and mortality 22 . T2D is associated with the gain of fat mass and can generate obesity, particularly central obesity. This may lead to an increased release of free fatty acids due to its high sensitivity through the action of catecholamines, which can produce a greater vasoconstriction and fluid retention, leading to hypertension 23,24 . Moreover, it is known that obese individuals usually have more difficulty to move around, join mobility reduction, and/or difficult to execute simple tasks of daily life such as climbing stairs 25 . The lack of regular physical activity in these pathological groups during their lives 26 could have contributed to a worse quality of strength, higher BMI (obese) and BP levels observed in the present study (TABLE 1).
The regular practice of physical exercise, or even Discussion a single exercise session, is one of the most nonpharmacological treatments used to prevent and/ or reduce the advancement of hypertension and T2D 27,28 . In this sense, one useful method that can be used to achieve the benefits for diabetic subjects is the RE since it promotes cardio-metabolic and neuromuscular adaptations 29 . In this context, stimulation and a very good prescription of the physical exercise are necessary to this population. The knowledge about the best moderate RE intensity that should be prescribed to improve physiological benefits can help to control blood glucose and BP levels.
Resistance exercise at 75% 1RM performed by D group resulted in a significant reduction of its glycemic level. This result was in agreement with previous findings where exercise with higher intensity was better to control blood glucose level 30,31 , even existing another study showing that regardless of intensity (low or moderate), an acute blood glucose uptake will be observed after a resistance circuit exercise 32 . This data of the present study indicated that with more intensive stimulation (until the upper limit of the moderate intensity), more blood glucose uptake is obtained, corroborating others studies 31,32 .
Some hormones such as catecholamine, cortisol, and glucagon increase as the exercise intensity raised, what may result in an increase of the liver glycolysis, increasing the blood glucose availability 33 . However, even with this hormonal pattern, the high-moderate exercise intensity performed at 75% 1RM resulted in an adequate stimulus for increasing blood glucose uptake by the active muscles, resulting in a reduction of BP after exercise. Moreover, the cortisol levels after exercise performed at 75% 1RM presented a significant reduction. The insulin sensibility increases after exercise due to an improvement of PI3-K and AKT activity, among others possibilities such as interleukins activation 34 . The high-moderate intensity probably resulted in more vigorous muscle contraction than low-moderate intensity, resulting in a higher blood glucose uptake as observed in the present study, what can explain that the muscle is considered the major body tissue capable to use blood glucose to generate biological energy 30,35 .
BP level is associated with many health risk factors and diseases including T2D 36 . The exercise sessions applied in the present study resulted in acute BP benefits for all groups (FIGURE 2) and PEH has been observed in normotensive, hypertensive 37,38 , and diabetic individuals being well described in the literature 35,36,39 .
Acute resistance circuit exercise is better than aerobic exercise to control BP during the 24h after exercise in diabetic subjects 6 , an acute circuit of RE is better than aerobic exercise to control BP during the 24h after exercise in diabetic subjects.
Asano et al. 22 in a review study suggest as the exercise intensity increases it is possible to observe a higher PEH. Basically, the studies reviewed by these authors were conducted utilizing exercises at light and/or moderate intensities. A greater PEH for the highest intensities when analyzed light and moderate intensities, independently if the exercise was aerobic or resistance 31,39,40 . Part of these results can explained by the nitric oxide levels since a highintensity exercise protocol is capable to induce nitric oxide release in hypertensive older women 41 .
On the other hand, Motta et al. 42 did not observe significant PEH for diabetics, suggesting a possible positive relationship between PEH and plasma kallikrein activity, since there was less kallikrein activity for diabetics. However, the exercise model was not RE and it was performed 10% below of their anaerobic threshold. According to Dutra et al. 43 , the PEH can influenced by many variables, including the exercise intensity.
In the present study, the acute exercises performed at 75% and 60% 1RM were capable to induce PEH in D groups with a better BP kinesis after exercise performed at 75% 1RM, which is considered a moderate exercise since a few relevant scientific studies have shown that the high RE intensity starts at 80% 1RM 37,44 . The ACSM suggests RE at 60% 1RM for hypertensive and diabetic individuals, and American Heart Association describe it should be over 60% of the maximum intensity 14 .
As observed in the present study, good results in both moderate exercise intensities used were found, but the results revealed to be better at 75% 1RM. A new division or subdivision in moderate RE could be proposed and further studies to confirm our findings are necessary to assess whether the changes in RE intensity affects the results.
It is important to note that the total volume of the resistance exercise at 60% and 75% 1RM were not differed (p>0.05) between the four groups (ND60, ND75, D60, D75), revealing the effects of intensity on metabolic and hemodynamic variables. Similar to the present study, an acute RE session of higher intensity followed by an oral glucose tolerance presented lower glycemia and insulinemia than lower intensity, even with a similar total volume of exercise sessions 45 .
In relation to hormonal kinetics, Kim et al. 46 demonstrated that healthy individuals who performed a high-intensity RE presented elevated testosterone levels as observed in our present study, even in different intensities (FIGURE 3A). However, it is also described that testosterone can be reduced in RE 10 . Our results revealed an increase of the testosterone plasma level in D groups after both moderate intensities. Higher testosterone levels in response to RE is associated with a necessary adaptation of the organism, especially at an increased intensity 47 .
Cortisol levels were significantly reduced in ND groups and in D group who performed RE at 75% 1RM (FIGURE 3B). Cortisol reduction was also observed in the elderly population after performing RE at 50% and 80% 1RM 48 , as reported by Uchida et al. 49

in women.
Our results reveal a positive relation of T:C ratio in moderate RE at both intensities for D groups, indicating anabolic parameter was immediately active. It might be higher at 75%1RM to help to repair the physiological stress observed through a higher muscle damage at this intensity, even they were not obtaining at their peak level after exercise. T:C ratio was increased in our study, showing a prevalence of anabolic conditions over catabolic, corroborating the data found by Uchida et al. 49 .
T2D pathology influences and promotes the increase of serum markers of muscle damage 50 for rest values. In the present study, there was only 79% of the maximum intensity, could divided into two or more sub sessions such as lower moderate and upper moderate training zones. Further studies, diagnosing physiological responses at 60%, 65%, 70%, 75% and 79% 1RM, for example, would give us a better idea about the differences in these physiological changes at the moderate training zone. Our data reinforce the importance of RE as a non-pharmacological treatment for T2D, mainly because of the improvement in the blood glucose uptake and the BP reduction after one single session of RE at 75%1RM.
The moderate resistance exercise at 75% 1RM promotes better blood glucose uptake and BP management in diabetic subjects. Moderate exercise at 60% or 75% 1RM is capable to reduce BP after RE to diabetic and hypertensive subjects. The testosterone and cortisol hormones after these RE in moderate intensities suggest the existence of an appropriated exercise recovery, especially after 75% 1RM that results in higher values of indirect muscle damage markers. There is no acute increase in C-RP after moderate RE intensities at 60 and 75% 1RM.
Acute RE brings benefits to diabetics who are hypertensive. Thus, higher intensity of RE targeting over 75% 1RM can performed without risk to the individual. Besides, the results found in this study, it is always necessary that diabetic hypertensive individuals to be supervised during all period of their training sessions for safety reasons. Acute RE at 60% or 75% of 1RM can be used as an extra tool to help the management of both pathologic conditions combined (diabetes and hypertension).
concomitant and significant increase of CK and LDH in higher amounts of moderate RE, revealing a greater muscle damage in T2D hypertensive individuals at 75%1RM. It is possible that the greatest amount of CK found after RE was due to a constant trial of the organism to restore the energy reserves during the exercise protocols 9,51,52 . The largest amount of LDH could be justified by an increase of the anaerobic work, disposing of more lactate in blood, once the exercise performed at a higher intensity can activate three times more LDH, contributing to a possible greater expression of glucose transporters and improving, on this way, insulin sensitivity 53,54 .
The analysis of muscle damage associated with the elevation or the lowering of inflammatory proteins, such as C-RP, may help to diagnose the best type of RE to be developed. The C-RP is release in greater quantities in the body when there is a proinflammatory activity in progress that can be caused by bacteria, viruses or simple metabolic stress provided by physical activity, for example 55,56 . The acute RE at any level of moderate intensity in this study was not able to generate a severe pro-inflammatory activity to increase beyond the point of reference standards C-RP levels. This result indicates that there is no contraindication for using moderate RE at 60% or 75% 1RM in an RE program for diabetics or non-diabetics.