Post by Yungchien "Amiao" Chu on Aug 7, 2005 17:40:56 GMT -6
Dr. Fleisig, I found that most indoor baseball pitching studies used a video sampling rate between 200 to 240Hz, while the outdoor studies usually used 120Hz. Do you think there is any recommended frame rate when conducting a baseball pitching study? What was the criterion, in your experience, to choose a certain video frame rate? Did you do some pilot research to find out a lower limit of frame rate to get valid data?
Also, while 60Hz miniDV handycam could be not enough for even qualitative analysis (Rochelle et al., 2003), it might be the only type of device that a common coach can afford. Since high speed cameras have not only high price but low portability, do you think a handycam can be used on subjects with young age and lower skill level, such as little league players, because of their low arm speed?
Post by Glenn Fleisig, Ph.D. on Aug 17, 2005 11:14:20 GMT -6
First, let me apologize for the slow response. ASMI is in the process of moving, so our computer server and connectivity is up and down right now.
ASMI staff and students have asked me the very same question before. In my opinion, the frame rates for most such studies are set by the limitations of the equipment available, not by a decision to reduce frame rate. In other words, indoor studies are often 200Hz or 240 Hz because the researchers had 200+ equipment in their lab, while outdoor experiments are 120Hz or so because this is the highest rate that their outdoor cameras/recorders can handle.
As far as what frame rate is needed to study pitching, I would suggest you find and read this study:
Glenn S Fleisig, Rafael F Escamilla, James R Andrews, Tomoyuki Matsuo, Yvonne Satterwhite, Steve W. Barrentine: Kinematic and kinetic comparison between baseball pitching and football passing. J Applied Biomechanics 12(2):207-224, 1996
In the Discussion section of this study, there is a comparison of results from pitching data at 200 Hz and 67Hz. You will see that some upper extremity variables (in particular, shoulder internal rotation velocity) are noticeably lower for the 60-ish samples/second data than for the 200-ish samples/second data.
Post by Yungchien "Amiao" Chu on Aug 28, 2005 10:32:12 GMT -6
Dr. Fleisig, I appreciate your email noticing me the reply.
I've read the article you suggested, and according to the article, it seems for the fastest motion in pitching, the shoulder internal rotation, can not be measured correctly using a 60Hz video camera. But for slower motion such as elbow extension, the angular velocity can be measured at around 95% using a handycam. Since youth pitchers have similar shoudler internal rotation angular velocity to adults (Fleisig et al., 1999), we can not using handycams quantifying their shoudler angular motion.
However, since Matsuo et al. reported max knee extension velocity during pitching was around 140~240 deg/s, almost 1/10 of elbow extension, the motion of lower body of pitching may be quantified well in 60Hz.
Another question is, for a sampling rate at 120Hz in outdoor settings, it is enough to get good measurement comparing to 200Hz? This might be answered using a similar method in the article you mentioned. Sadly I don't have proper equipment to do this. While you said the 120Hz sampling rate was due to the limitation of equipment, I guess they may use Peak System with highest sampling rate at 120Hz, which is the only equipment our lab has.