The most common site of back pain is in the lumbar (lower back) area.
        
             
        
        
        
This is True, if your heart isn't strong enough it's hard to stretch, lift weights, breathe, perspire.
        
             
        
        
        
Answer:
When you don't have proper body alignment, then the curl ups could be too easy or too hard. 
This could also cause injury, due to improper stretching of the muscles. 
Some tips would be: (<em><u>You may choose any two of them</u></em>)
1.) keep your feet about 12 inches/1 foot aways from your bottom. 
2.) Stretch properly before doing curl ups to prevent injury. 
3.) Lay on something soft to prevent spine aching/injury. 
4.) Instead of putting your hands behind your head, put them in an X shape across your chest. This can prevent neck injury or aching. 
5.) Don't let your feet lift off the ground, have a friend hold them down. Never put gym weights on them, as that can cause injury to your feet. 
 
        
             
        
        
        
The stage of the heart cycle in which the heart muscle is relaxed<span>, allowing the chambers to fill with blood. ... The </span>stage of the heart cycle in which the heart muscle<span> contracts and the chambers pump blood. Systolic Pressure. Blood pressure in the arteries during contraction of the ventricles</span>
        
                    
             
        
        
        
HPV has a huge link to  cancer in those that are infected with it