A study from the U.S. Army Research Institute of Environmental Medicine led by Bradley Nindl showed that growth hormone increases were greater during a two-hour aerobic workout than during a one-hour aerobic workout, one-hour weight workout, or two-hour weight workout.
A study from the University of São Paulo in Brazil showed that simultaneously training for strength and endurance did not alter gene activity associated with muscle hypertrophy.
Ronald Snarr and Michael Esco, from the University of Alabama and Auburn University, found that performing planks with the TRX device or Swiss balls provided greater loads to the core muscles than traditional stable planks.
A study led by Jakob Vingren from the University of North Texas in Denton found that a kettlebell swing workout consisting of 12 sets of swings with a 16-kilogram kettlebell for 30 seconds, followed by 30 seconds of rest, triggered substantial increases in testosterone, growth hormone, cortisol, lactate, heart rate and perceived exertion that were consistent with intense physical training.
A study from the University of Georgia led by Nicholas Gist found that performing four sets of burpees at maximum intensity for 30 seconds, followed by four minutes of rest, produced a physiological load that was similar to HIIT workouts on a stationary bike.
A study from the University of Memphis, led by Brian Schilling and Matt McAllister, showed that the glute-ham raise and Romanian deadlift were the best exercises for activating the hamstring muscles.
A similar study by Mike Smith and co-workers showed that CrossFit training, involving high-intensity resistance training and aerobics, also caused positive changes in aerobic capacity, strength and body composition.
A study by scientists from Iran, Ohio State University and Texas A&M University found that chain training was superior to traditional weight training for building lower body strength.
The safety of squats has been questioned for more than 50 years. The National Strength and Conditioning Association, in a position stand, stated that squats are safe if performed correctly.