PURPOSE This study investigated the effect of non-linear periodization strength training on basic and professional fitness of national cross-country skiers. METHODS The body composition (height, weight, BMI, body fat %), basic physical strength (grip strength, lung capacity), anaerobic power (peak power, average power), graded exercise test (maximum heart rate, running time, VO2max, lactic acid), isokinetic strength (trunk strength), and 1RM (bench press, dead-lift, squat, shoulder press, leg curl, bicep curl, cable triceps extension) of nine national cross-country skiers (male: 5, female: 4) were measured. All analyses were performed using SPSS 25.0, Kruskal-Wallis H tests were applied to observe the changes by training methods. Mann-Whitney U tests were used as Post Hoc. RESULTS The results indicated that running time and VO2max post-test improved compared to that for the pre-test for graded exercise test. The lumbar extension strength of the post-test was higher than that for pre-test. There was no significant difference in other variables. CONCLUSIONS It is suggested that nonlinear periodization strength training can be expected to improve running time, VO2max, and trunk strength for cross-country athletes; however, it does not affect the overall changes.
