"Friends don't let friends miss ab day! #makingithappen #vacaworkout," she captioned the snap posted on Saturday.
She wore a strappy white bikini top and bottoms made by swimwear brand Mikoh.
She slicked back her long tresses in a ponytail and shielded her eyes from the sun with a pair of aviator sunglasses.
In another photo, she boasted about her athleticism by showing her 431,000 social media followers that she could do a plank even with a boot and most impressively on a surfboard in the ocean. Lindsey opted for a black bikini set as she put her forearms and feet on the board.
"#SUP this boot can't slow me down!!" she commented along with the photo.
Along with a glowing tan, it appears Vonn had acquired some new henna ink across her chest.
She suffered a painful ankle injury during a training run in New Zealand last week.
Vonn proved that not even injury could stop her from having fun and maintaining her athletic physique in her latest Instagram snaps.
Holding herself up with suspension training straps, the blonde beauty can be seen sticking her tongue out while she dons black shades.
She explained in the picture caption: "So I had planned to go on vacation with my girlfriends and I almost canceled it because I hurt my ankle.... but then I decided that spending time with my friends and being injured was better than being alone and injured".
She added: "But just because I'm on vacation doesn't mean I'm not working hard :) #girlstrip #herewego @gopro #trx"
She had revealed her injury on Instagram days before as she wrote: "See ya later New Zealand #meandmywheelchair #mybestpoutface #ankleproblems #30hoursuntiligethome."
She then added a snap of her painful, swollen ankle captioned: "#nofilter #sohotrightnow."
Her trip had started on a far more positive note as she previously wrote: "And so it begins....on my first flight of many on my way to New Zealand. Winter is a long ways away ;) #bethereintwodays #cantwaittoski."