I think that strength training is vital to getting good photos. By that, I dont mean you need to be a record breaker at dead-lifting. If you have a D3s and a 70-200 on your shoulder, You will be uncomfortable unless you are an elephant!
I am 31 and have been working out since I was 12 years old. So I don't notice the weight too much. Most of my weddings and event are at least 6 hours floor time. I invested in a black rapid double strap this year. It has made a massive difference. I will carry as practice, D3s 24-70mm a D700 with 70-200mm and I will have an SB900 on my belt with 2 spares left in the bag.
I did a wedding last weekend and was on my feet for 9 hours. I didn't feel to bad by the end of the day.
If any of the exercise phobic are looking at gaining physical strength without getting a gym membership, basic exercises will help improve you longevity in any one given photo shoot. Its worth doing something.
The key body parts that you use are: Your core: Lower back and Abs, your legs and your arms. I bet that if someone was getting tired taking photos over periods of time, that a very simple exercise plan would make a huge difference.
Try this if its you, (if you are medically fit)
Sit-ups 3 sets of 20 reps
Lower back raises 3 Sets of 15 (lie on your belly on the floor, put your hands behind your head and lift your head slowly of the floor extending you chin away from the floor.
Lungs 3 sets of 15 reps. Stand static, step forward with one leg to create a 90 degree angle,
Squats 3 sets of 15
and lastly bicep curls with a couple of bags a sugar.
All free and all without weights. You will notice a difference if you don't exercise regularly.
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