The purpose of this study was to determine the contribution of different in-season strength and power training frequencies to strength and power performance over the course of a 22 week rugby league competition period. Twenty-eight male (n=28) participants, with both high and low strength pre-training status, were divided into three groups following a 15 week pre-season strength and power training programme. A four week periodised in-season strength and power training programme, with intensities ranging from 75-100%, was cycled for the 22 week competition season. Strength and power training was conducted one day.week(-1) by the first high pre-training status group (HTFL, n=11), and two day.week(-1) by the second high pre-training status group (HTF2, n=9). The low pre-training status group (LTF1, n=8) performed the same strength and power training frequency and programme as HTF1. Training intensity (% 1RM) and volume (sets x repetitions) of in-season strength and power training sessions were standardised for both groups during each training week. Strength, power, and speed data were collected pre-season, and four times during the in-season period. No differences were found between HTF1 and HTF2 in performance variables throughout the 22-week in-season period. Both HTF1 and HTF2 displayed similar significant detraining effects in strength, power, and speed, regardless of in-season training frequency (p<0.05). LTF1 showed no change from pre-season strength and power performance following 22 weeks of the competition period (p<0.05). It was concluded that in-season strength and power training frequency may have a limited role in determining the success of the in-season strength and power training programme in highly trained footballers. The results of the present study suggest a number of factors other than in-season strength and power training frequency may affect in-season strength and power performance and detraining in high strength pre-training status athletes. The effect the start of a competition period has on dynamic athletic performance needs further investigation.