"Elastic Heart" peaked at number 7 on the singles chart of New Zealand and was certified 3× Platinum by the Recorded Music NZ.

The solo version was released in 2015 as a single from the album and was accompanied by a controversial music video that features actor Shia LaBeouf and dancer Maddie Ziegler.

[2] A power ballad,[3] the main vocal hook is a chopped sample from Billy Stewart's 1957 recording "Baby, You're My Only Love", while the drumline is an altered take from Jacky Giordano's 1975 instrumental "Magolia".

[7] Its lyrics address "the overwhelming strength Sia needed to convince herself that life was worth living after coming out of a crushing relationship.

[8] Blue Sullivan of Slant Magazine wrote that "'Elastic Heart' is a seamless and highly successful team-up that reads like a grimier after-market version of Lady Gaga's 'Do What U Want'.

"[9] Spin magazine's Chris Martins stated that "Sia soared" and it was a "bubbling ballad,"[10] and Bradley Stern of MuuMuse claimed it was "a perfectly chaotic combination.

[14] The song fared better in New Zealand, peaking at number 7 on the national singles chart and was certified gold by the Recorded Music NZ (RMNZ).

Club labelled "Elastic Heart" a "striking power ballad,"[3] while AllMusic's Heather Phares picked the song as one of the three standouts from the album, alongside "Chandelier" and "Eye of the Needle".

[50] Jason Lipshutz from Billboard summarised: "The entirety of the video features the surprising pair interpreting the song through different body contortions: they dance-fight, collapse in the middle of the cage, crawl toward and away from each other, and make some wildly fantastic facial expressions.

[56] The video "courted controversy and plaudits in equal measure", with some commentators perceiving it to have pedophilic undertones because it features an adult and child dancing together clad only in beige dancewear.

[61]On 17 January 2015, Sia performed "Elastic Heart" on Saturday Night Live with Kevin Hart hosting and Maddie Ziegler and Denna Thomsen dancing.

[62] For the performance, Sia sang the song with a short black veil covering the top half of her face, while Ziegler and Thomsen recreated the dance routine in the music video wearing nude leotards and blonde wigs.