IntroductionConcurrent training can best be described as an attempt to combine endurance training and strength training within one training program in the aim to simultaneously improve strength and endurance. When we think about the term interference, we may sometimes associate it with a conflict between two or more identities, strength training is often used due to the highly anaerobic nature of the activity, in order to achieve certain physiological results that may be beneficial for sports performance (Harries, Lubans & Callister, 2012). In team games, strength and conditioning coaches use exercises in a gym, which they hope will lead to adaptations in muscle size, strength and hypertrophy. To do this, coaches must offer suitable training programs that do not cause unnecessary fatigue for the athlete and that suit the demands of the sport and the wishes of the technical coach. In rugby there are many areas of training where there are demands for both anaerobic and aerobic exercise; the ability to perform well in both aspects is therefore desirable (Impellizzeri, Rampinini & Marcora, 2005; Maud, 1983; Morton, 1978). During the interference effect, certain aerobic workouts that players may perform (such as a 2 km run) may have detrimental effects on the ability to perform anaerobic activity later (Hickson, 1980 and Hunter, Dement & Miller, 1987). be due to an accumulation of hydrogen ions in the muscle (Cooke, Franks, Luciani & Pate, 1988). Hickson (1980) suggests that during a strength training program, adding endurance training to the same program inhibits improvement in muscle strength. DiscussionNeuralSometimes there is no sign of interference between: training f...... middle of paper ..... . depletion of muscle glycogen and a reduction in pH at the cellular level (Coyle et al., 1983; Sahlin, Tonkonogi & Söderlund, 1998). During moderate to high intensity anaerobic exercise, fatigue may be linked to a reduction in pH level, with depletion of ATP stores and depletion of muscle glycogen playing a small role (Reilly, 1997). During very high intensity exercise, fatigue may occur due to increased ADP, inorganic phosphate, or reduced muscle pH, but a specific cause is difficult to identify (Lambert and Flynn, 2002 ). Other limiting factors could include the effect of metabolic acidosis, limiting the production of contraction force of a muscle (Bogdanis, Nevill, Lakomy & Boobis, 1998), the accumulation of ammonia (Brouns, Beckers , Wagenmakers & Saris, 1990) and the reduction in the capacity of the sarcoplasmic reticulum to release calcium (Favero, 1999).