Effect of Different Instructional Strategies on Respiratory Muscle Performance

Participants will perform ventilatory muscle training (VMT) using the POWERbreathe Kinetic K5 device in four experimental conditions: 1. Control: no additional instructions (only basic technical instructions). 2. Explicit instruction: verbal instructions focused on the body (e.g., ‘expand your rib cage without raising your shoulders’). 3. Instruction by analogy: viewing a video of a balloon expanding inside a rib cage, asking the participant to replicate that pattern. 4. External focus: instruction to concentrate on improving the values shown on the screen during inspiration. The POWERbreathe Kinetic K5 is an electronic inspiratory muscle training (IMT) device that provides variable and controlled resistance during inspiration. It uses an electronic valve that adjusts the load based on the user's inspiratory flow, allowing for precise, progressive and reproducible training, as well as recording parameters such as inspiratory pressure, volume and power. Participants perform respiratory training by breathing in through the device's mouthpiece, usually in a seated position. During the sessions, they are instructed to take deep, controlled breaths following the established protocol (number of breaths, sets and breaks), while the device monitors and stores the training data. The instructions will be provided by the investigator. results collected by POWERbreathe Kinetic K5 displayed on a television screen in front of participants, etc. The study is randomised. The duration of each session was approximately 30 minutes per participant. The ventilatory muscle training (VMT) focused specifically on the accessory muscles of inspiration: the sternocleidomastoid and the scalenes. The sternocleidomastoid acts to elevate the sternum, while the scalene muscles elevate the first and second ribs. Together, they expand the upper thoracic cavity during increased ventilatory demand. The training involved exercises designed to target and engage these specific muscle groups. The intervention was administered by an investigator who is a Professor at the University of Seville, holding a degree in Sports Science and Physical Activity. No video was used or shown during the 'instruction by analogy' condition. The instruction relied entirely on the participants' own mental imagery and internal visualization. All participants began the study by completing the control condition first. Following the control session, the remaining three conditions were assigned to each participant in a randomized order. For both the 'explicit instruction' and 'instruction by analogy' conditions, the instructions are provided only once during the 30-minute session. The exact timepoint at which this single instruction is delivered depends on the randomized sequence of the instructional strategies assigned to the participant.