Athletes who wear a weighted vest continuously for a few weeks become noticeably fitter and faster. But there's an easier way, sports scientists from the University of Jyvaskyla conclude in a study that will soon appear in the Journal of Strength and Conditioning Research. According to the Finns, it probably makes no difference if you take the weighted vest off when you're not training.
Weighted vests are not a hype. As long ago as the 1980s scientists discovered that athletes could achieve better training results by wearing a weighted vest that increases their own weight by 11 percent. In a study done in the same decade, subjects wore a weighted vest for three weeks, from morning to evening, not only while training but also during all their daytime activities. [Acta Physiol Scand. 1985 Aug; 124(4): 507-13.] At the end of the experiment they jumped 24 percent higher.
In another study done around the same time, endurance athletes wore a weighted vest for four weeks, once again for the whole day. [Eur J Appl Physiol Occup Physiol. 1987; 56(4): 412-8.] At the end of the four weeks their speed, oxygen uptake and endurance capacity had all increased by a statistically significant amount.
In a more recent study, Tunisian researchers achieved similar results when they got basketball players to wear weighted vests for several weeks, but only when training. [J Strength Cond Res. 2010 Nov; 24(11): 2955-61.] When they weren't training the subjects didn’t wear the vests.
The researchers wanted to know whether the weighted vests have any effect when you're not training. If people who don't exercise regularly wear a vest while making tea, fetching the newspaper or getting up from their desk, does the vest have any effect?
The researchers got 8 sedentary men to wear a Finnish Hasanen Power Wear weighted vest three days a week for three weeks. [power-wear.com] The vests weighed 4-6 kg. A control group of nine men wore no special clothing.
The muscle and fat mass of the men in the weighted-vest group didn't change. The researchers also observed no change in power and speed during exertion tests. The men who had worn weighted vests did have a faster speed for a short figure-of-8 running test. So their manoeuvrability had increased a little.
The measured effect was pretty modest. So wearing a weighted vest during ordinary daily activities probably has little added value. Which means you really only need to wear one during training sessions.
"Based on the existing literature, it appears that a proper volume and intensity could be in the order of 5 - 10% body weight vest worn during training sessions for a period of 3 to 4 weeks", the researchers conclude.
The Finns were financed by the Academy of Finland, not by a weighted-vest manufacturer.
J Strength Cond Res. 2012 Jan 20. [Epub ahead of print].