Influence of acute and chronic streptozotocin-induced diabetes on the rat tendon extracellular matrix and mechanical properties.

Diabetes is a major risk factor for tendinopathy, and tendon abnormalities are common in diabetic patients. The purpose of the present study was to evaluate the effect of streptozotocin (60 mg/kg)-induced diabetes and insulin therapy on tendon mechanical and cellular properties. Sprague-Dawley rats (n = 40) were divided into the following four groups: nondiabetic (control), 1 wk of diabetes (acute), 10 wk of diabetes (chronic), and 10 wk of diabetes with insulin treatment (insulin). After 10 wk, Achilles tendon and tail fascicle mechanical properties were similar between groups (P > 0.05). Cell density in the Achilles tendon was greater in the chronic group compared with the control and acute groups (control group: 7.8 ± 0.5 cells/100 µm(2), acute group: 8.3 ± 0.4 cells/100 µm(2), chronic group: 10.9 ± 0.9 cells/100 µm(2), and insulin group: 9.2 ± 0.8 cells/100 µm(2), P < 0.05). The density of proliferating cells in the Achilles tendon was greater in the chronic group compared with all other groups (control group: 0.025 ± 0.009 cells/100 µm(2), acute group: 0.019 ± 0.005 cells/100 µm(2), chronic group: 0.067 ± 0.015, and insulin group: 0.004 ± 0.004 cells/100 µm(2), P < 0.05). Patellar tendon collagen content was ∼32% greater in the chronic and acute groups compared with the control or insulin groups (control group: 681 ± 63 µg collagen/mg dry wt, acute group: 938 ± 21 µg collagen/mg dry wt, chronic: 951 ± 52 µg collagen/mg dry wt, and insulin group: 596 ± 84 µg collagen/mg dry wt, P < 0.05). In contrast, patellar tendon hydroxylysyl pyridinoline cross linking and collagen fibril organization were unchanged by diabetes or insulin (P > 0.05). Our findings suggest that 10 wk of streptozotocin-induced diabetes does not alter rat tendon mechanical properties even with an increase in collagen content. Future studies could attempt to further address the mechanisms contributing to the increase in tendon problems noted in diabetic patients, especially since our data suggest that hyperglycemia per se does not alter tendon mechanical properties.

Blood pressure-lowering efficacy of a 6-week multi-modal isometric exercise intervention.

Isometric exercise training (IET) is an effective method for reducing resting blood pressure (BP). To date, no research studies have been conducted using multiple exercises within an IET intervention. Previous research has suggested that varied exercise programmes may have a positive effect on adherence. Therefore, this randomized controlled study aimed to investigate the BP-lowering efficacy of a multi-modal IET (MIET) intervention in healthy young adults. Twenty healthy participants were randomized to an MIET [n = 10; four women; SBP 117.9 ± 6.9 mmHg; DBP 66.3 ± 5.1 mmHg] or control (CON) group (n = 10; five women; SBP, 123.3 ± 10.4 mmHg; DBP, 77.3 ± 6.7 mmHg). The MIET group completed three sessions per week of 4, 2-min isometric contractions, with a 1-min rest between each contraction, for 6 weeks. Resting BP and heart rate (HR) were measured at baseline and post-intervention. Pre-to-post intervention within-group reductions in resting BP were observed (SBP: 5.3 ± 6.1 mmHg, DBP: 3.4 ± 3.7 mmHg, MAP: 4.0 ± 3.9 mmHg, HR: 4.8 ±6 .6 bpm), although clinically relevant (≥2 mmHg), these changes were not statistically significant. Significant (p < 0.05) between-group differences were found between the intervention and control groups, indicating that the MIET intervention has a greater BP-lowering effect compared to control. The clinically relevant post-training reductions in resting BP suggest that MIET may be a promising additional IET method for hypertension prevention. These findings; however, must be interpreted with caution due to the small sample size and the non-clinical cohort.

Characterization of resting and exercise inter-arm differences in SBP to isometric handgrip exercise in males and females.

A large inter-arm difference (IAD; ≥10 mmHg) in SBP is linked to cardiovascular and peripheral vascular disease, hypertension, and premature mortality. Exercise-induced IAD (eIAD) is related to resting IAD, and acute aerobic activity alters eIAD and reduces IAD in recovery. Isometric handgrip exercise (IHE) affects blood pressure (BP), though the eIAD response to IHE is unknown. Further, the eIAD response may differ between males and females. OBJECTIVES: To characterize the eIAD response to IHE in males and females. METHODS: On visit 1, participants (16 females and 15 males, aged 18-35 years) completed three maximal voluntary isometric contractions (MVIC) per arm. On visit 2, before IHE, a series of three simultaneous, bilateral BP measures were averaged at rest. During IHE, participants maintained handgrip at 20% of MVIC for 2 minutes (arm randomly assigned), at which time bilateral BP was measured (IHE) during exercise and subsequent recovery (REC1 and REC2). Repeated-measures analysis of variance assessed eIAD and SBP (time × sex). RESULTS: IHE increased absolute eIAD (4 mmHg). Differences in relative eIAD were observed at IHE and REC2 based on resting IAD status (P < 0.05). Females only had an exaggerated SBP and pulse pressure response in the working arm. CONCLUSION: Acute IHE was shown to augment eIAD. Further eIAD and resting IAD were related. Acute IHE induced different bilateral responses between males and females, though the impact of sex on eIAD warrants further investigation. Future studies should address the effects of repeated bouts of IHE, which may benefit individuals with a large resting IAD.

"Get a Grip on Hypertension": EXPLORING THE USE OF ISOMETRIC HANDGRIP TRAINING IN CARDIOPULMONARY REHABILITATION PATIENTS.

PURPOSE: Isometric handgrip (IHG) training lowers systolic and diastolic blood pressure (SBP and DBP, respectively), but the efficacy of IHG training in cardiopulmonary rehabilitation patients is unknown. The purpose of this study was to determine if IHG decreases blood pressure in cardiopulmonary rehabilitation patients. METHODS: Cardiopulmonary rehabilitation program participants (n = 11; 50-80 yr old) were randomized to IHG (n = 6) or control (CON; no treatment; n = 5) groups. IHG participants completed an IHG training program at 30% maximal voluntary contraction, 3 d/wk for 6 wk. Resting SBP, DBP, and heart rate were assessed weekly. RESULTS: Mean regression for SBP following IHG was negative (-1.04 ± 0.80). Mean regression in the CON group was positive (0.50 ± 0.88), but there was no significant difference between groups. Separate analysis of weeks 1 to 7 yielded a negative mean regression (-1.12 ± 0.54) in the IHG group, but positive (1.2 ± 0.60) in the CON group. A Wilcoxon test of these differences yielded significance for SBP (P = .009). In 3 of 6 IHG participants, SBP was lower (mean ± SD: -16 ± 11 mm Hg; P = .12), and in 2 IHG participants, DBP was lower (-9 ± 1 mm Hg; P = .06) compared with baseline. In 2 of 5 CON participants, SBP was not significantly lower (-11 ± 7 mm Hg) and, in 3 of 5 CON participants, DBP was lower (-7 ± 4 mm Hg; P = .04). CONCLUSIONS: Our data suggest that standard IHG training may be inadequate for blood pressure management immediately following a major cardiac or pulmonary event. Future work with a larger cohort and more developed training protocol to determine the efficacy of IHG training in patients with cardiopulmonary disease is warranted.

A comparison of blood pressure reductions following 12-weeks of isometric exercise training either in the laboratory or at home.

Isometric exercise training (IET)-induced reductions in resting blood pressure (RBP) have been achieved in laboratory environments, but data in support of IET outside the laboratory are scarce. The aim of this study was to compare 12 weeks of home-based (HOM) IET with laboratory-based, face-to-face (LAB) IET in hypertensive adults. Twenty-two hypertensive participants (24-60 years) were randomized to three conditions: HOM, LAB, or control (CON). IET involved isometric handgrip training (4 × 2 minutes at 30% maximum voluntary contraction, 3 days per week). RBP was measured every 6 weeks (0, 6, and 12 weeks) during training and 6 weeks after training (18 weeks). Clinically meaningful, but not statistically significant reductions in RBP were observed after 12 weeks of LAB IET (resting systolic blood pressure [SBP] -9.1 ± 4.1; resting diastolic blood pressure [DBP] -2.8 ± 2.1; P > .05), which was sustained for 6 weeks of detraining (SBP -8.2 ± 2.9; DBP -4 ± 2.9, P > .05). RBP was reduced in the HOM group after 12 weeks of training (SBP -9.7 ± 3.4; DBP -2.2 ± 2.0; P > .05), which was sustained for an additional 6 weeks of detraining (SBP -5.5 ± 3.4; DBP -4.6 ± 1.8; P > .05). Unsupervised home-based IET programs present an exciting opportunity for community-based strategies to combat hypertension, but additional work is needed if IET is to be used routinely outside the laboratory.