Pure2improve Black Sprintsac, Sports Direct. The Pure2Improve Sprint Sac is extremely ideal for resistance training, running with the additional resistance of the weight will make you a stronger runner, meaning it will not only improve your speed and endurance but will also strengthen your joints, burn more calories, improve bone health, improve body posture and also makes you less likely to get sports-related injuries. The Sprintsac includes: 3x high-quality and durable 5kg sandbags (sand not included), belt and bag. The maximum weight of the Pure2Improve Sprintsac is 15 kg. This weight is reached by filling the three sandbags with sand, 5 kg each. This is the maximum they can handle. The weight of the Sprint Sac can be adjusted by not using all the sandbags or leaving sand out of the bags. This makes the Pure2Improve Sprintsac suitable for both beginners and advanced users. The Pure2Improve Sprintsac is connected to the waistband through a cord. In this way, the athlete can drag the Sprint Sac behind him and built-up resistance during the training. The cord is adjustable in length and the waistband can be set to the right size by Velcro. The Pure2Improve Sprintsac is made of smooth material and has rounded corners. Because of this, it slides smoothly over the floor. The sandbags are closed with Velcro. The Sprint Sac strengthens and focuses on the lower-body muscle groups, simply adjust the weight options for a variety of weight resistance. Overall, the Sprint Sac Trainer set increases the difficulty and the resistance of your workout, taking your workout to that extra level!Looking for alternatives to stores like JD Sports, eBay, SHEIN, ASOS, Next, Best Choice UK, Very, Decathlon UK, Argos, schuh, Temu, BuyBetter, or Nike Official? Discover our unique selection.