I noticed that while I'm in good so called shape (BMI wise) I have no strength or endurance during training. I can't punch hard or punch hard for long. My question is about improving endurance and strength but before you guys recommend anything (or tell me to RTFM here is a little background... I'm 40 years old, 5.10 and 152 lbs. Very healthy but also very new. I just started (loving) boxing and kick boxing. I have no prior martial arts background and I don't remember when I was in a gym last time (maybe 20 years ago). My goal (with taking up boxing and kick boxing) is simply to be in better shape (mentally and physically) with some interest in self-defensive applications. Since I'm old(er) and this is just a (serious long term) hobby for me I'm trying to be very carefully about injuries which take longer to recover from (its a gift of getting older). Keeping all that in mind... what recommendations would you guys make for somebody like me who wants to be stronger and have more endurance? Thanks for all suggestions in advance and... be gentle.