Human activity recognition, for example as done with the Sports-1M Dataset, is a classification task. Given a video, say which activity / action was executed.
So it is a special case about video classification.
human activities like swinging the arm are sequential actions and they require LSTMs
This is wrong. As a simple example, think of handwriting ...
If your using computer vision, the top recognised conference is CVPR (computer vision and pattern recognition).
You can also try to submit at ICML (International conference on machine learning) and NIPS (Neural Information Processing Systems), which focuses on applications of machine learning and deep learning.
I'd also recommend IJCAI (International joint ...