This will read a text file into memory:
install.packages('readr')
library(readr)
filename <- filename <- '/Users/gsieling/Downloads/4c1b9688-1a7a-4236-ae70-0bf7b3f30192_1/DI_CONNECT/DI-Connect-Fitness/gary.sieling@gmail.com_0_summarizedActivities.json'
read_file(filename)