Resistance exercise training is one of the popular exercise modes that has been drawn the public's attention. However, existing evidence showed high-intensity resistance exercise training-induced negative adaptation on vascular function and blood pressure responses. Upper-body resistance exercise training is more likely to induced arterial stiffening, which has been shown to be gender-dependent. It is still unknown whether age also plays a role. We like to test the hypothesis that high-intensity upper body resistance exercise may lead to a higher increase of arterial stiffness, central blood pressure, and hemodynamic parameters in younger adults than older adults. We also hypothesize high intensity resistance training could contribute to greater central hemodynamic responses and muscle stiffness than the control; the change of muscle stiffness correlates with the change of hemodynamic parameters. Collectively, study 1 in this project is aimed to recruit 40 apparently healthy young (20-35yrs) and middle-aged to older adults (50-75yrs) into this study followed by upper-body or lower-body high-intensity exercise (80% 1 repetition maximum, 10 reps, 4 sets) by a randomized order. Blood draw, central blood pressure, hemodynamics will be performed and obtained at pre-, immediately-post, 20min, 40mins, and 60 mins post-exercise. Study 2 is aimed to investigate the effects of 8-week whole-body resistance exercise training followed by a 4-week detraining on above-measured variables in order to determine the long-term effects on resistance training. We will employee state-of-art ultrafast ultrasound to obtain muscle stiffness and carotid local pulse wave velocity. Endothelin-1 and catecholamines will also be measured to discover its underlying mechanisms on such stiffening effects induced by high-intensity resistance exercise.

Inclusion Criteria:

• Healthy middle-aged to older adults

Exclusion Criteria:

• (1)BMI≧27, (2) Smoking habits for more than six months in the past, (3) Hypertension (blood pressure>140/90 mmHg), (4) Personal diabetes history (fasting blood sugar >126 mg /dL), heart disease, or other cardiovascular diseases, (5) bone damage, (6) regular use of supplements or vitamins