Kettlebells should be a tool in everyone’s kit these days. After all, everyone from Lance Armstrong to US Airforce Pararescuemen use them- so whatever your athletic vocation, you can benefit from them. They provide a number of options in an easy to carry form. Recently, cardiovascular training via kettlebell has become popular. A 2010 study by Farrar et al found that a 12 min 16kg swing routine had the athletes working at 86.8% MaxHR, they were also generally working at 65.3% of VO2max. The relationship between heart rate and VO2 that we associate with running, cycling and other cardiovascular activities seems to break down in this case. Clearly, for heart rate training and circulatory effects, kettlebells can be used. They would not be my go to tool for VO2 training. Don’t neglect their effects on strength, explosiveness and muscular endurance- which is where the emphasis should be used. Good kettlebells also have thick handles which will train the grip, an added benefit.