Does Intra-abdominal Pressure Have a Causal Effect on Muscle Strength of Hip and Knee Joints?

Interaction of breathing pattern and posture on abdominal muscle activation and intra-abdominal pressure in healthy individuals: a comparative cross-sectional study

We aimed to assess the effects of interaction between several breathing patterns and postures on abdominal muscle activation and intra-abdominal pressure (IAP). This comparative cross-sectional study enrolled fourteen healthy university students majoring in sports science and/or physical education. They performed four active breathing tasks: quiet nasal breathing (Q-Bre), nasal deep breathing (Deep-Bre), completely forced expiration (Forced-Expi), and exertional nasal inhalation with abdominal muscles with isometric contraction (Exertion-Inspi) in the elbow-toe plank and supine postures. Breathing volume; IAP; and transverse abdominis-internal oblique muscle (TrA-IO) and external oblique muscle (EO) activities were recorded. Abdominal muscle activity and IAP significantly interacted with breathing pattern and postures during the expiratory phase (p < 0.05). In the inspiratory phase, TrA-IO activity was significantly affected by breathing pattern and EO activity with posture (p < 0.05). TrA-IO activity significantly increased during Forced-Expi in the supine posture (47.6% of the maximum voluntary contraction) and Exertion-Inspi in the elbow-toe posture (35.7%), whereas no differences were found during Deep-Bre or Q-Bre (< 20%). EO activity increased in the elbow-toe posture (22.5-30.6%) compared with that in the supine posture (< 5%) during all breathing tasks. IAP values were low during all tasks (< 15%) except for Forced-Expi (24.9%). Abdominal muscle activation and IAP interacted with the breathing pattern and posture.

The control of respiratory pressures and neuromuscular activation to increase force production in trained martial arts practitioners

PURPOSE

The mechanisms that explain the ability of trained martial arts practitioners to produce and resist greater forces than untrained individuals to aid combat performance are not fully understood. We investigated whether the greater ability of trained martial arts practitioners to produce and resist forces was associated with an enhanced control of respiratory pressures and neuromuscular activation of the respiratory, abdominal, and pelvic floor musculature.

METHODS

Nine trained martial arts practitioners and nine untrained controls were instrumented with skin-surface electromyography (EMG) on the sternocleidomastoid, rectus abdominis, and the group formed by the transverse abdominal and internal oblique muscles (EMG_tra/io). A multipair oesophageal EMG electrode catheter measured gastric (P_g), transdiaphragmatic (P_di), and oesophageal (P_e) pressures and EMG of the crural diaphragm (EMG_di). Participants performed Standing Isometric Unilateral Chest Press (1) and Standing Posture Control (2) tasks.

RESULTS

The trained group produced higher forces normalised to body mass^2/3 (0.033 ± 0.01 vs. 0.025 ± 0.007 N/kg^2/3 mean force in Task 1), lower P_e, and higher P_di in both tasks. Additionally, they produced higher P_g (73 ± 42 vs. 49 ± 19 cmH₂O mean P_g) and EMG_tra/io in Task 1 and higher EMG_di in Task 2. The onset of P_g with respect to the onset of force production was earlier, and the relative contributions of P_g/P_e and P_di/P_e were higher in the trained group in both tasks.

CONCLUSION

Our findings demonstrate that trained martial arts practitioners utilised a greater contribution of abdominal and diaphragm musculature to chest wall recruitment and higher P_di to produce and resist higher forces.