Procedures
BLOOD, CONTRACTIONS
A familiarization session was conducted 2–5 days before the first experimental session. In this session the anthropometrics of the participants were measured, the training equipment was adjusted to the individual and these setting were noted, the participants tried the three different training modalities (two minutes per modality), and they were introduced to the different scales for affective measures.The resistance training for the finger flexors was conducted on a custom-made apparatus (Fig. Before each test session the participants followed the same warm-up protocol consisting of 10 min of easy, but progressive bouldering. The general warm-up was followed by a specific warm-up on a fingerboard, consisting of four contractions (50–80% of self-perceived maximum) lasting five seconds each. Afterwards, the participants performed two maximal voluntary contractions (MVC) on the apparatus, each lasting 5 s. A rest interval of 60 s separated the attempts. The MVC was performed to calculate the target zone-threshold of the different sessions and was conducted on each test day to account for day-to-day variability. Each training session consisted of three sets and started five minutes after the last MVC. Each set consisted of isometric, intermittent contractions that lasted for seven seconds and were separated by three seconds of rest. The arms and fingers were kept in position throughout the set. The participants were instructed to keep the force close to the set intensity, however, some fluctuations were allowed if they stayed within the target zone (defined as ± ten percent of the set intensity). Each set was performed until failure, being defined as two seconds of continuous force output below the lower limit of the target zone for that specific session. Only the completed repetitions were included in the calculation of training volume, i.e. the seconds of the uncompleted final repetition were excluded.The design of the different training sessions was similar to other studies comparing heavy resistance training with blood flow restriction training at low intensitiesThe blood flow restriction was applied using two inflatable cuffs (Occlude, Blood flow restriction exercise, Denmark, (width: 9 cm x length: 38 cm)). This brand of cuffs has shown good reliability both between sessions (ICC 0.86 and CV 5.7%) and rater (ICC 0.98 and CV 3.2%), when measuring occlusion pressure for the upper body while standing up