## 4 Discussion
We also determined that increases in O2 Hb during slow rowing under 140 mmHg were significantly higher than those during fast rowing under the same cushion pressure, and increases in O2 Hb tended to be higher under 140 mmHg than under 0 mmHg and 80 mmHg during slow rowing (\(p=0.095\)). As mentioned, cushion pressure of 140 mmHg resulted in a relatively unstable surface, and fast rowing was not conducive to tissue oxygenation and blood volume of the erector spinae. Therefore, as displayed in Figures 3 and 4, the increases in tissue oxygenation and blood volume were lowest under 140 mmHg during fast rowing. Additionally, Figure 3 indicates that slow rowing under three different seat cushion pressure levels better maintained blood volume and tissue oxygenation than medium and high rowing cadences did. Therefore, slow rowing was more conducive to tissue oxygenation and blood volume of the erector spinae during the recovery period because it helped maintain oxygen concentration and increase blood volume. The different pressure levels were also important factors. In the present study, the magnitude of HR decrease during fast and medium rowing were significantly larger than those during slow rowing. The previous study demonstrated that larger decreases in HR during the recovery period after exercise were associated with higher exercise intensity [36]. Increased HR during the exercise period was significantly larger during fast and medium rowing than during slow rowing; therefore, decreases in HR during the recovery period were also greater. RPE had similar trends; decreases in RPE during the recovery period under all pressure levels were significantly higher during fast rowing than during slow rowing. At a medium rowing cadence, decreases in RPE during the recovery period were significantly greater under 140 mmHg than under 0 mmHg or 80 mmHg. This could be because at the same rowing cadence, the RPE under 140 mmHg tended to increase more during exercise, thus leading to a greater decrease in recovery. The results of the present study can be used to provide exercise suggestions related to nonresistance rowing exercises to enhance blood volume to the back muscles and improve cardiopulmonary workouts. Because a beginner's movement familiarity, muscle strength, muscular endurance, and cardiorespiratory fitness are poor, we suggest that beginners use slow rowing to develop movement skills and physical fitness. If the purpose of the exercise is to effectively increase the tissue oxygenation and blood volume of back muscles, we recommend using seat cushion pressure under 140 mmHg with a low rowing cadence (stroke rate: 18 bpm). If an individual is familiar with the related movements, has an adequate level of physical fitness, and seeks to strengthen their cardiopulmonary function and increase their tissue oxygenation and blood volume of the back muscles, we recommend using seat cushion pressure under 80 mmHg with a high rowing cadence (stroke rate: 36 bpm). Recreational boating is a popular leisure activity in western countries (ex: USA) Recreation boats include several types of power boats (ex: pontoon boats, PWCs, open power boats), canoe, kayaks, paddleboards, row boats, and so on [37]. The present study demonstrated that rowing cadence affects the tissue oxygenation and blood volume of the erector spinal muscle, HR, and RPE during exercise and recovery period. Therefore, the present study results do not apply to recreation boating except rowed boats with controlled rowing cadences. The present study had three limitations. First, it only analyzed changes in tissue oxygenation and blood volume of the erector spinae and several physiological parametersduring 10 strokes, which did not meet the requirement of at least 10 min of cardiopulmonarymann stimulation [38]. The second limitation is that the present study did not investigate rowing ergometer resistance load. In the present study, HR increased by 20-30 bpm during exercise and RPE increased by 0.38-1.17, which indicates that this was a relatively effortless rowing test.