Critical stroke rate as a parameter for evaluation in swimming

Kinematic and electromyography characteristics of performing butterfly stroke with different swimming speeds in flow environment

Objective

To investigate effect of flow speeds on the upper limb muscular activity of butterfly swimmers training in a flow environment. A comparison of kinematic characteristics and muscular activity of upper limbs were made when the swimmers training with different flow speeds in a swimming flume. The purpose was to provide a basis for scientifically formulating special swimming training advice for athletes' training in flow environment.

Methods

Ten youth female butterfly swimmers participated in the study with the speed of 70%, 80%, and 90% level of their max speeds. A stroke cycle was divided into four phases (entry, pull, push, and recovery). The kinematic parameters of upper limbs (stroke rate, stroke length, duration of each phase in a stroke cycle) and muscular activity (onset timing, integrated electromyography (iEMG), contribution ratio) of four muscles (Biceps brachii (BB), Triceps brachii (TB), Pectoralis major (PM), and Latissimus dorsi (LD)) were collected and analyzed in different stroke phases.

Results

There was no significant difference between stroke rate and stroke length with different flow speeds. There were significant differences among the duration of the four stroke phases. The entry phase had the longest duration, the pull phase had the shortest duration, the push phase was longer than the recovery phase, and the recovery phase was shorter than the entry phase. The BB and PM were activated significantly earlier at 90% of target speed than at 80% of target speed, while the TB was activated significantly later than other two speeds. The muscular contribution ratio of the PM was highest in the pull phase and lowest in the pushing phase. The muscular contribution ratio of the BB was significantly lower in the pushing phase than in other three stroke phases. The muscular contribution of the TB was significantly higher in the recovery phase than in other three stroke phases. The muscular contribution ratio of the LD was highest in the pushing phase, and it was significantly higher in pushing phase and recovery phase than in pull phase.

Conclusions

(1) When butterfly athletes training with 70%, 80% and 90% of their max speed in a flow environment, it didn't make significant differences between the kinematic or muscle activation characteristics of the upper limbs movement except the muscle onset timing. (2) Stroke phase was the main factor of the duration and the muscle contribution ratio during butterfly arm stroke for young athletes.

Efficacy of Core Training in Swimming Performance and Neuromuscular Parameters of Young Swimmers: A Randomised Control Trial

Background: This study aimed to investigate the efficacy of core training in the swimming performance and neuromuscular properties of young swimmers. Methods: Eighteen healthy male swimmers (age: 13 ± 2 years, height: 159.6 ± 14.5 cm, weight: 48.7 ± 12.4 kg) were recruited from the Public Authority for Sports swimming pool in Dammam and randomly assigned to the experimental and control groups. The experimental group performed a six-week core-training program consisting of seven exercises (three times/week) with regular swimming training. The control group maintained its regular training. Swimming performance and neuromuscular parameters were measured pre- and post-interventions. Results: The experimental group benefitted from the intervention in terms of the 50 m swim time (−1.4 s; 95% confidence interval −2.4 to −0.5) compared with the control group. The experimental group also showed improved swimming velocity (+0.1 m.s−1), stroke rate (−2.8 cycle.min−1), stroke length (+0.2 m.cycle−1), stroke index (+0.4 m2·s−1), total strokes (−2.9 strokes), and contraction time for erector spinae (ES; −1.5 ms), latissimus dorsi (LD; −7 ms), and external obliques (EO; −1.9 ms). Maximal displacement ES (DM-ES) (+3.3 mm), LD (0.5 mm), and EO (+2.2 mm) were compared with the baseline values for the experimental group, and TC-ES (5.8 ms), LD (3.7 ms), EO (2.5 ms), DM-ES (0.2 mm), LD (−4.1 mm), and EO (−1.0 mm) were compared with the baseline values for the control group. The intergroup comparison was statistically significant (p < 0.05; DM-ES p > 0.05). Conclusion: The results indicate that a six-week core-training program with regular swimming training improved the neuromuscular properties and the 50 m freestyle swim performance of the experimental group compared with the control group.

Physiological Responses and Stroke Variables during Arm Stroke Swimming Using Critical Stroke Rate in Competitive Swimmers

The current study examined the physiological responses and stroke variables at critical stroke rate (CSR), 105% CSR, and 110% CSR in order to utilize CSR for prescription arm stroke swimming. Nine male national-level collegiate swimmers performed an all-out 200 m and 400 m for determining the CSR. Participants performed three sets of 6 × 100 m (with 10 s of rest between each bout), the stroke rate for each set was enforced at CSR, 105% CSR, and 110% CSR. Mean swimming velocity, heart rate, and rate of perceived exertion were found to increase with each set (p < 0.05). Blood lactate concentration did not differ between the CSR and the 105% CSR (3.3 ± 1.4 vs. 3.5 ± 1.5 mmol/L) but was higher in 110% CSR (5.1 ± 1.6 mmol/L) than in the other two sets (p < 0.05). There was no difference in the stroke rate between all bouts in each set, and the stroke length did not change from the second to sixth bout in each set. This study suggested that training intensity for CSR and 105% CSR correspond to threshold level, and 110% CSR corresponds to high-intensity training level. It was also suggested that training in the CSR−110% CSR range could be performed without regard to SL reduction.

Individualizing Training in Swimming: Evidence for Utilizing the Critical Speed and Critical Stroke Rate Concepts

PURPOSE

To monitor physiological, technical, and performance responses to individualized high-intensity interval training (HIIT) prescribed using the critical speed (CS) and critical stroke rate (CSR) concepts in swimmers completing a reduced training volume program (≤30 km·wk-1) for 15 weeks.

METHODS

Over the 15-week period, 12 highly trained swimmers (age 16 [1] y, height 179 [8] cm, weight 66 [8] kg) completed four 3-minute all-out tests to determine CS and the finite capacity to work above CS (D'), and four 200-m tests at CS to establish a CSR estimate. Combining CS and D', 2 HIIT sessions designed as 5 × 3-minute intervals depleting 60% of D' and 3 × 3.5-minute intervals depleting 80% of D' were prescribed once per week, respectively. An additional HIIT session was prescribed using CS and CSR as 10 × 150 m or 200 m at CS with 2 cycles per minute lower stroke rate than the CSR estimate. Additional monitored variables included peak speed, average speed for 150 seconds (speed150s) and 180 seconds (speed180s), competition performance and stroke length (SL), stroke count (SC), and stroke index (SI) adopted at CS.

RESULTS

At the end of the intervention, swimmers demonstrated faster CS (mean change ± 90% confidence limits: +5.4 ± 1.6%), speed150s (+2.5 ± 0.9%), speed180s (+3.0 ± 0.9%), and higher stroke rate (+6.4 ± 3.0%) and stroke index (+4.2 ± 3.6%). D' was reduced (-25.2 ± 7.5%), whereas peak speed, SL, and SC changed only trivially. The change in the swimmers' personal best times in the first and second main event was -1.2 ± 1.3% and -1.6 ± 0.9%, respectively.

CONCLUSION

HIIT prescribed based on the CS and CSR concepts was associated with improvements in several physiological, technical, and performance parameters in highly trained swimmers while utilizing time- and resource-efficient approach. This was achieved despite a ≥25% reduction in training volume.