Depends on the activity. Each sport has its own measures of performance. I suggest you select a specific sport and then conduct background research on performance. You should be able to find some lab measures you can use. Or you can do a longer study on actual performance vs a control.

i select football players. 

how can i the performance?

is there any scientific method to judge or only players physical perfomance on field??

Field performance would be a better measure, but you could also design experiments for in-lab analysis. For instance for a quarterback you could evaluate the reaction time, speed, and accuracy of a throw. 

thanks Derek for good suggestions. 

what about the lab experiments? 

should i design  these experiments in software?

and if i design these experiments in software, than what about the validation of these experiments???

Search the lit for people who have studied football already. There should be a few lab measures that have already been used.