Hemodynamic Responses to Resistance Exercise in Patients with Coronary Artery Disease.

PURPOSE: Investigate hemodynamic responses of resistance exercise (RE) with moderate load (i.e., international guidelines for RE of patients) versus RE with high load in patients with coronary artery disease (CAD). METHODS: Medically stable male (n = 11) and female patients (n = 4) treated with PCI or percutaneous coronary intervention, or coronary artery bypass surgery a minimum of 6 months before this study, performed three sets of 15RM and 4RM RE in a randomized order on separate days. Beat-to-beat systolic (SBP), diastolic (DBP) blood pressure, heart rate (HR), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) were monitored at preexercise, and continuously during RE. RESULTS: Compared with preexercise, SBP and DBP (mean of three sets) increased by 12% to 13% (both; P < 0.001) and 35% to 40% after 15RM RE (both; P < 0.001). 15RM SBP and DBP were higher than 4RM SBP and DBP (both; P < 0.001). The SBP of the fourth repetition of 15 RM RE was similar to the SBP of the fourth repetition of 4RM RE. Compared with preexercise, SV increased moderately after 4RM and 15 RM RE, respectively (both, P < 0.001). HR increased more after 15RM compared with 4RM RE (P < 0.05); thus, higher CO after 15RM (compared with 4RM RE; P < 0.05) was mainly caused by higher HR. SVR decreased by 15% (P < 0.001) and 50% (P < 0.01) after 4RM and 15RM RE. CONCLUSIONS: SBP and DBP increased significantly more during moderate load RE; thus, the magnitude of the external load is not the prime determinant of the pressure response during RE. If management of blood pressure is of concern, high load/low rep RE is preferable to medium load/high rep RE.

Effect of training with different mechanical loadings on MyHC and GLUT4 changes.

PURPOSE: There is an inverse relationship between insulin sensitivity and percentage of myosin heavy chain IIx (MyHC IIx) isoform in sedentary, obese, and type 2 diabetic humans. How different exercise conditions may reduce the proportion of MyHC IIx and in parallel elevate glucose transporter 4 (GLUT4) content is interesting in a therapeutic setting. This study investigates the nature of exercise signals regulating MyHC gene switching and whether it is accompanied by GLUT4 changes. METHODS: Thirty-two subjects performed high loading (60% of 1 repetition maximum [RM]) or low loading (30% of 1 RM) elbow extensions in a training apparatus and exercised three times per week for either 5 wk (low volume) or 8 wk (high volume). MyHC and GLUT4 contents in the musculus triceps brachii were measured by Western blotting pre- and posttraining and after 8 wk of detraining. RESULTS: All training regimes resulted in MyHC IIx changes of similar magnitude, and differences in training volume had no effect on the outcome. The reduction in MyHC IIx content after high loading, high volume was similar to low loading, matching volume of training. Thus, there was no effect of training load on MyHC changes. GLUT4 increased more after high than low loading (P < 0.0.1). In addition, the larger increases in the GLUT4 were associated with the larger reductions in MyHC IIx content (r = -0.56, P < 0.01). Detraining returned GLUT4 to baseline, but MyHC IIx content was still higher than baseline (P < 0.01). CONCLUSION: Magnitude of loading is not important for suppression of MyHC IIx but for increases in GLUT4 content. The GLUT4 content responded, however, more rapidly to detraining than the MyHC IIx and IIa isoforms.

Effect of training with different intensities and volumes on muscle fibre enzyme activity and cross sectional area in the m. triceps brachii.

This study primarily examined how intermittent versus continuous endurance training, using similar or dissimilar volumes, affected muscle fibre enzyme activities in the triceps brachii muscle. Thirty-two subjects performed either intermittent (60% of 1RM) or continuous (30% of 1RM) elbow extensions 3 times week(-1) in a training apparatus. Training was performed until either a low (five) or a high volume (8 weeks) was accumulated. Muscle biopsies from the m. triceps brachii were taken pre- and post training and following 8 weeks of detraining. Marker enzymes for muscle fibre oxidative (succinate dehydrogenase SDH) and glycolytic (glycerophosphate dehydrogenase; alpha-GPDH) capacity was assessed by histochemistry, and the resulting enzyme activities measured by image analysis. The type of training affected enzyme activities differently. In type 1 fibres, continuous and intermittent training was equally effective in increasing SDH activity, while intermittent training increased SDH activity more than continuous training in type 2 fibres (P < 0.05). Intermittent training increased alpha-GPDH activity more than continuous training both in type 1 (P < 0.001) and type 2 fibres (P < 0.05), but the increase in glycolytic capacity following intermittent training was larger in type 1 (54%) than in type 2 fibres (23%). There was no effect of training volume on oxidative or glycolytic capacity in either fibre type. Thus, when training intensity is sufficient to stimulate to increases in oxidative and glycolytic capacity, the SDH and alpha-GPDH response seems to be volume independent. Detraining reduced Post-T enzyme activities to baseline (all; P < 0.01).

Effect of training and detraining on the expression of heat shock proteins in m. triceps brachii of untrained males and females.

Forty untrained persons were randomized to four different training protocols that exercised the m. triceps brachii. Group 1 and 2 performed high intensity (HI) elbow extensions and group 3 and 4 performed low intensity (LI) elbow extensions. Group 1 and 3 trained until they had accumulated a matching high volume (HV) of training, while group 2 and 4 trained until they had accumulated a matching low volume (LV) of training. Training for 5-8 weeks increased the HSP72, HSP27 and GRP75 levels in the subjects' m. triceps brachii by 111, 71 and 192%, respectively (Fig. 1a-c). There were, however, no significant differences in the heat shock protein (HSP) responses to training between the four training groups (Fig. 2a-c). The frequency of extreme responses to exercise was, however, higher after HI exercise than after LI exercise, indicating that HI exercise induces extreme HSP reactions in some subjects. When we assigned the subjects to three clusters, according to the total number of repetitions they had lifted, the subjects who had lifted the highest number of repetitions had lower PostExc HSP levels compared with subjects that lifted the lowest number of repetitions (Fig. 3a-c). Additionally, there was a negative non-linear regression (Fig. 4a-c) between the subjects PreExc levels of HSP72, HSP27 and GRP75 and the percentage change in their respective protein concentration after training (r = -0.75, -0.89 and -0.88, all P < 0.0001). Thus, the PreExc level of HSPs seems to be an important "regulator" of HSP expression following the training.

Effect of concentric or eccentric weight training on the expression of heat shock proteins in m. biceps brachii of very well trained males.

Increased HSP expression in response to acute exercise is well documented in animal studies, and there is growing evidence that similar responses occur in man. In general, many human exercise studies have investigated the HSP response to low force continuous activity, while the knowledge about the HSP response to high force intermittent type of activity, like weight training, is so far sparse. In addition, most studies have used untrained subjects, and a common observation is that acute low force continuous activity in untrained individuals increases the HSP expression in these individuals. The main scope of this study was to investigate the HSP response in very well trained males subjected to longitudinal high intensity exercise, and if this response was dependent on exercise modality [i.e. eccentric (ECC) or concentric (CON) contractions]. Very well trained males performed progressive strength training consisting of either high force ECC or high force CON elbow flexions 2-3 times a week for 12 weeks. Compared with pre-exercise levels, HSP72 expression decreased by 46.1% (P<0.05) after CON contractions. GRP75 expression was unchanged after ECC or CON contractions, while ubiquitin expression decreased by 19.9% (P<0.02) after ECC contractions. These findings imply that chronic, intensive exercise may attenuate the HSP response in well-trained males.