Low-load resistance training with hypoxia mimics traditional strength training in team sport athletes

Abstract

IntroductionSport scientists, athletes and coaches recognize that resistance training is integral for improving muscular strength, however the ideal training regime for strength improvement is debatable. Muscular strength is a key factor in many sports, not only for improvement in physical performance but also for the prevention of injury (Kraemer & Fleck, 2005). Muscle strength and size gain is dependent on the type of exercise and intensity of resistance as well as training volume of the strength training program. Workloads of at least 65% of one repetition maximum (1RM) are required to achieve a substantial increase in strength. However, training benefits can be obtained throughout the RM range. High-loads (> 80% of 1RM) are used when the goal is maximum strength gain, moderate (> 50% of 1RM) for hypertrophy and muscle power enhancement, and low-loads (> 20% of 1RM) for muscular endurance (American College of Sports, 2009; Hillman SK, Perrin DH., 2005). Even though high resistance loads are commonly used by athletes, such training may result in muscle, ligament and tendon injury (Raske & Norlin, 2002) and reduced central arterial compliance (Miyachi et al., 2004) which may increase systolic blood pressure. In addition, some people are not able to lift such heavy weights (injured athletes, bed-rest patients, etc.). Therefore, to promote safe resistance training (avoid muscle injury and reduce risk of dangerous blood pressure changes) and to assist those who cannot perform high-load resistance exercise, low-load resistance exercise has been utilized by sport scientists in combination with other strategies such as venous occlusion and simulated altitude or hypoxia. Using low-load resistance exercise alone, has little adaptive effect on muscular strength, however, combined with either venous occlusion or hypoxia, low-load resistance training results in increased stress on the musculature which forces the muscle fibres to adapt and strengthen (Wernbom, Augustsson, & Raastad, 2008). As such, low-load resistance exercise (20-50% of 1RM), in combination with venous occlusion, has been proposed as an alternative to high-load resistance exercise7.Similar to venous occlusion in combination with low-load resistance training, recent studies have reported an enhancement in muscle strength after low-load resistance exercise combined with hypoxia (Manimmanakorn, Hamlin, Ross, Taylor, & Manimmanakorn, 2013). It is thought that during venous occlusion the blood flow restriction probably causes substantial hypoxia (Downs et al., 2014; Loenneke & Pujol, 2009; Manini & Clark, 2009) which may play a key role in muscle adaptation (Manimmanakorn et al., 2013; Scott, Slattery, Sculley, & Dascombe, 2014), thus training under hypoxic conditions may be responsible for the increased force, endurance and size of the muscle rather than the reduced blood flow per se.To date, there has been little research exploring what resistance loads when combined with hypoxia, produces the optimal strength adaptation and whether such training is superior to the standard practice of 80%1RM training under normoxia. Therefore, this study aimed to investigate the effectiveness of 5 weeks of two different low resistance training loads (30%, or 50%1RM) combined with hypoxia (compared to low-load 30%1RM and conventional resistance training of 80%1RM in normoxia) on muscle strength, endurance and physical performance.MethodsParticipantsForty high performance team sports athletes (males aged 20.2 ± 1.7 years, soccer = 27, hockey = 3, basketball = 10) volunteered for this study. All athletes completed the Physical Activity Readiness Questionnaire and a skill-related physical fitness test. All athletes met the inclusion criteria as follows: they reported no exposure to an altitude of > 1,000 m within the last 3 months, no history of severe acute mountain sickness, no contraindicative health conditions, or medications (e. …