The Effects of an Intensive 2-wk Resistance Training Period on Strength Performance and Nocturnal Heart Rate Variability.
PURPOSE
It is known that modifying the endurance-type training load of athletes may result in altered cardiac autonomic modulation that may be estimated with heart rate variability (HRV). However, the specific effects of intensive resistance-type training remain unclear. The main aim of this study was to find out whether an intensive 2-wk resistance training period affects the nocturnal HRV and strength performance of healthy participants.


METHODS
Young healthy men (N = 13, age 24 [2] y) performed 2-wk baseline training, 2-wk intensive training, and a 9-d tapering periods, with 2, 5, and 2 hypertrophic whole-body resistance exercise sessions per week, respectively. Maximal isometric and dynamic strength were tested at the end of these training periods. Nocturnal HRV was also analyzed at the end of these training periods.


RESULTS
As a main finding, the nocturnal root mean square of differences of successive R-R intervals decreased (P = .004; from 49 [18] to 43 [15] ms; 95% CI, 2.4-10.4; effect size = 0.97) during the 2-wk intensive resistance training period. In addition, maximal isometric strength improved slightly (P = .045; from 3933 [1362] to 4138 [1540] N; 95% CI, 5.4-404; effect size = 0.60). No changes were found in 1-repetition-maximum leg press or leg press repetitions at 80% 1-repetition maximum.


CONCLUSIONS
The present data suggest that increased training load due to a short-term intensive resistance training period can be detected by nocturnal HRV. However, despite short-term accumulated physiological stress, a tendency of improvement in strength performance was detected.
['Kaikkonen|Piia|P|', 'Hynynen|Esa|E|', 'Hautala|Arto|A|', 'Ahtiainen|Juha P|JP|']
D000328:Adult D001341:Autonomic Nervous System D006339:Heart Rate D006801:Humans D008297:Male D053580:Muscle Strength D010807:Physical Endurance D055070:Resistance Training D055815:Young Adult
training load autonomic nervous system cardiac vagal modulation muscle strength training programming