## 3 Results  
Figure 2 demonstrates that prior to and during the bicycle ergometer test (Study A), there were no statistically significant differences in HR between the two age groups. HR progressively increased with each workload level and subsequently decreased during the recovery phase in both groups. The highest HR was recorded at 200 W, reaching \(156.1\pm 3.7\) ppm in the under-45 group and 160.5 \(\pm\) 3.7 ppm in the over-45 group. A statistically significant difference between groups emerged at the second minute of recovery: HR decreased to 126.8 \(\pm\) 3.7 ppm in the younger group and to 117.0 \(\pm\) 4.2 ppm in the older group (\(p\) < 0.05). Despite this reduction, HR values in both groups remained above baseline after three minutes of recovery. Based on HR data, participants under 45 showed a faster return to baseline levels after physical exertion compared to those over 45. Effect size analysis indicated a moderate difference in HR recovery at 2 and 3 min post-exercise, suggesting better cardiovascular recovery in the younger group. During the local intermittent loading protocol (Study B), HR dynamics differed. Compared to exercise, HR increased during recovery periods. Statistically significant differences between age groups were observed from the first to the last recovery stage (\(p\) < 0.05). At the first rest interval, HR in the under-45 group was 92.4 \(\pm\) 4.0 bpm, while the over-45 group reached 106.0 \(\pm\) 5.0 bpm (p < 0.05). During the second repetition, HR decreased slightly to 89.7 \(\pm\) 2.4 bpm and 100.0 \(\pm\) 3.7 bpm in the younger and older groups, respectively (\(p\) < 0.05). A subsequent increase was observed during the second rest period, with HR reaching 95.3 \(\pm\) 4.0 bpm in the under-45 group and 108.0 \(\pm\) 4.6 bpm in the over-45 group (\(p\) < 0.05). This upward trend continued in the third repetition and rest phase. HR during the third repetition increased in the under-45 group to 94.4 \(\pm\) 2.7 ppm and 103.0 \(\pm\) 2.2 bpm in the over-45 group (\(p\) < 0.05). The third rest period exhibited the highest HR values of this protocol: 99.1 \(\pm\) 3.4 bpm in the under-45 group and 109.5 \(\pm\) 3.5 bpm in the over-45 group (\(p\) < 0.05). Figure 3 shows that at the onset of exercise, sBP in Study A progressively increased with each stage of the bicycle ergometer test and decreased during the recovery period. In Study B, sBP values returned close to baseline during the rest intervals between repetitions. No statistically significant differences in sBP were observed between age groups at any stage of testing or recovery. At baseline, sBP in Study A was 127.3 \(\pm\) 2.6 mmHg in participants under 45 years of age and 124.0 \(\pm\) 2.9 mmHg in those over 45. The highest values were recorded at the 200 W workload, reaching 188.8 \(\pm\) 5.9 mmHg in the younger group and 197.2 \(\pm\) 4.0 mmHg in the older group. During the local intermittent exercise protocol targeting the back muscles (Study B), sBP values during recovery were lower than baseline in both age groups. Baseline sBP was 124.4 \(\pm\) 3.1 mmHg in the under-45 group and 118.0 \(\pm\) 3.4 mmHg in the over-45 group. After the third repetition, sBP peaked during exercise, reaching 125.8 \(\pm\) 3.1 mmHg in the younger group and 123.3 \(\pm\) 5.1 mmHg in the older group. The lowest values were observed during the third rest phase: 122.9 \(\pm\) 2.4 mmHg in the under-45 group and 115.7 \(\pm\) 3.4 mmHg in the over-45 group. dBP at baseline in Study A was 79.7 \(\pm\) 2.4 mmHg for the younger group and 81.0 \(\pm\) 2.5 mmHg for the older group. A statistically significant difference between groups was observed at the 200 W workload: dBP decreased to 65.4 \(\pm\) 7.3 mmHg in the under-45 group and to 71.9 \(\pm\) 5.3 mmHg in the over-45 group (\(p\) < 0.05). One minute into recovery, dBP further dropped to 54.6 \(\pm\) 4.1 mmHg and 69.3 \(\pm\) 3.7 mmHg, respectively, again showing a statistically significant difference (\(p\) < 0.05). After three minutes of recovery, values did not return to baseline.