Michael Phelps won his 19th Olympic gold medal, the highest number by one athlete, after the American men’s team won the 4x100-meter relay event at Rio 2016. But more than the gold, the colour that dominated media reports and social media, was purple—the colour of the spots all over the swimmer’s body.

As it turned out, the circles were the result of cupping, a therapy technique that helps athletes recover faster.

Here’s a list of some of the most unusual healing techniques that athletes have used in the recent past to recover better between events.

Cupping: Cupping is an alternative form of therapy that has been practiced in China for thousands of years. The method is simple. Suction cups are used for creating vacuum on a person’s body, which pulls the skin from the body and boosts blood flow to the area.

There is, however, no conclusive summary of clinical research to prove its efficacy (or the lack of it). The American Cancer Society has said that the available scientific evidence does not support cupping as a cure for any disease and that any reports of successful treatment are “mainly anecdotal". But cupping could have more than just a placebo effect, concluded a 2012 study published in the journal PLoS ONE.

That said, an increasing number of athletes and performers have taken to cupping recently, including the US gymnastics team currently in Rio, and they swear by it.

Cryotherapy: Cryotherapy is, basically, an ice-bath taken to a different level. In whole-body cryotherapy (WBC), athletes enter a chamber in which the whole body, except the head, will be exposed to temperatures below -100 degrees Celsius. Like cupping, research on the efficacy of whole-body cryotherapy has yielded mixed results.

One study, published in the Scandinavian Journal of Medicine and Science in Sports in 2011 says that WBC, administered 24 hours after eccentric exercise, is ineffective in alleviating muscle soreness or enhancing muscle force recovery. Another study published in PloS One the same year, says WBC was effective in reducing the inflammatory process.

The Welsh rugby team used cryotherapy in the run-up to the 2011 Rugby World Cup. American athlete Justin Gatlin famously sampled WBC and had his feet frozen in the chamber.

CVAC pods: This is the method of choice for Novak Djokovic, the world’s No.1 tennis player. In 2011, he credited the egg-shaped pod and his gluten-free diet in equal measure for his remarkable turnaround on the court.

CVAC, short for Cyclic Variations in Adaptive Conditioning, uses a computer-controlled vacuum pump to simulate high altitude. This compression process reportedly helps athletes at a cellular level—it increases oxygen absorption and thereby promotes muscle recovery.

There aren’t many studies to prove the CVAC pod’s effect. Experts are divided. But at $75,000 per pod, this is not for everyone any way.

Horse placenta: Serbian healer Marijana Kovacevic is known as miracle woman in football circles. In 2014, Atletico Madrid striker Diego Costa was reported to have travelled to Belgrade to seek her help days before the Champions League final against Real Madrid. He was suffering a grade one hamstring tear and was doubtful for the match. It was a desperate bid by Atletico to get their star striker fit in time.

Kovacevic uses fluid from horse placenta, which she claims helps repair damaged cells quickly, to heal muscle injuries. On the night of the finals on 24 May, though, Costa lasted less than 10 minutes on the field. Kovacevic’s website names more than 100 athletes she has worked with, including English Premier League stars Robin van Persie and Frank Lampard.