Lung volumes, capacities and flow rates have been observed to be greater in high-intensity endurance sports like rowing, cycling, boxing, football, basketball, rugby and water polo in comparison to power, mixed and skill groups of sports [23]. In addition, studies have shown that elite rowers require extremely high levels of ventilation with them showing higher ventilatory parameters [3, 4].
In the present study, when comparing the pre and post-training values of ventilatory parameters, it was observed that PIF and FVC improved significantly in the experimental group (p < 0.05) while no improvements were observed in all lung parameters in the control group (p > 0.05) after the respective training programs (Table 1). Furthermore, PIF was significantly higher (p = 0.04) in the experimental group compared to the control group after the 12 weeks RMT program (Table 2). Several past studies have also shown similar findings with improvement in PIF following RMT using the RMT device [24, 25].PIF is known to be the fastest flow rate achieved during a maximum inspiration and provides a measure of the maximal contraction of the inspiratory muscles [26].
The novel RMT training program conducted in this study included profound (deep) inspirations and inspiratory hiccups, exercises that strengthen the inspiratory muscles, while isometric side bridge, curls ups improved expiratory muscles strength. In addition, it also included flexibility training to stretch the chest wall. These techniques would have helped to strengthen the respiratory muscles, improve the lung capacity (FVC) and PIF and increase chest expansion in the experimental group compared to the control group. These exercises have similarities with deep breathing techniques used in pranayama yoga practice during which the respiratory muscles are stretched fully towards the chest wall represented by increased chest wall expansion together with increased lung volumes, capacities and flow rates namely FVC, FEV1 and PEF in healthy subjects [13, 27, 28]. Long term benefits of yoga has been shown to increase chest expansion, breath-holding time and PEF [28, 29].
Healthy respiratory systems are anatomically well equipped to meet the oxygen requirements at rest and during increased exercise intensities. In the present study, significant improvement was seen in VO2maxovertime in both groups with only the experimental group showing significant improvements. No significant difference was observed in VO2maxbetween the two groups after the RMT program (p > 0.05). Many studies have examined the effect of RMT on VO2maxin different sports and revealed that VO2max was not altered by RMT while a small group of studies have shown a statistically significant decrease in sub-maximal O2 following RMT across different sports [25, 30].
When considering the relationship between ventilatory functions and performance it was observed that there was a negative relationship between lung functions and 2000 m and 5000 m ergometer performance in both groups in the present study. However, only PIF significantly correlated with 2000 m performance in experimental group. This indicates that higher PIF are associated with lower ergometer time performance. However, contradictory outcomes have been observed concerning the relationship of ventilatory functions with sports performance following RMT. One study in athletes’ documented that there was a significant negative relationship with FVC and running times [31] while in another study done on cyclists observed improvements in cycle endurance time subsequent with improved ventilatory functions following RMT [32].
When considering aerobic fitness, the present study revealed that there was a significant negative correlation between VO2 max, and 2000 m and 5000 m ergometer performance test in the experimental group (r= -0.68; p < 0.05) (Table 3) while in the control group only 2000 m performance was significant. Similarly, several past studies have reported a significant correlation between 2000 m ergometer rowing performance and VO2max values [33, 34].However, another study stated that no significant correlation exists between aerobic fitness and 2000 meter ergometer performance in both male and female rowers [35]. Though past research has consistently demonstrated that success in rowing is associated with higher VO2max, some studies stated that VO2max alone is not a good predictor of rowing performance in rowers with similar endurance capacity [4, 33].
The effect of RMT on lung functions and exercise performance has been inconclusive because of the differences in research design such as inappropriate performance outcome variables, ineffective RMT protocols, small sample sizes and the lack of carefully matched experimental and placebo groups [35]. Some studies have suggested that a well-designed case-controlled study with an appropriate RMT protocol [36] and self-motivation of athletes also contributes to a positive impact on exercise performance [8,24,].
Overall, our findings suggested that applying this novel RMT program in the training schedules of rowers resulted in improving some respiratory functions (PIF) and aerobic fitness and these were associated with greater performance in both 2000 m and 5000 m rowing ergometer tests. This highlights the importance of introducing RMT in training protocols of sportsmen and women in Sri Lanka, in addition to peripheral muscle training program, as a routine practice to improve the sports performance. This novel RMT could also be used in rehabilitation of clinical populations, especially in developing countries, as RMT devices are costly and inaccessible for many.