$$\dot{V}{\text{O}}_{ 2}$$ kinetics and metabolic contributions during full and upper body extreme swimming intensity

Purpose

Our purpose was to characterize the oxygen uptake (\(\dot{V}{\text{O}}_{ 2}\)) kinetics, assess the energy systems contributions and determine the energy cost when swimming front crawl at extreme intensity. Complementarily, we compared swimming full body with upper body only.

Methods

Seventeen swimmers performed a 100 m maximal front crawl in two conditions: once swimming with full body and other using only the upper propulsive segments. The \(\dot{V}{\text{O}}_{ 2}\) was continuously measured using a telemetric portable gas analyser (connected to a respiratory snorkel), and the capillary blood samples for lactate concentration analysis were collected.

Results

A sudden increase in \(\dot{V}{\text{O}}_{ 2}\) in the beginning of exercise, which continuously rose until the end of the bout (time: 63.82 ± 3.38 s; \(\dot{V}{\text{O}}_{{ 2 {\text{peak}}}}\): 56.07 ± 5.19 ml min^?1 kg^?1; \(\dot{V}{\text{O}}_{ 2}\) amplitude: 41.88 ± 4.74 ml min^?1 kg^?1; time constant: 12.73 ± 3.09 s), was observed. Aerobic, anaerobic lactic and alactic pathways were estimated and accounted for 43.4, 33.1 and 23.5 % of energy contribution and 1.16 ± 0.10 kJ m^?1 was the energy cost. Complementarily, the absence of lower limbs lead to a longer time to cover 100 m (71.96 ± 5.13 s), slower \(\dot{V}{\text{O}}_{ 2}\) kinetics, lower aerobic and anaerobic (lactic and alactic) energy production and lower energy cost.

Conclusion

Despite the short duration of the event, the aerobic energy contribution covers about 50 % of total metabolic energy liberation, highlighting that both aerobic and anaerobic energy processes should be developed to improve the 100 m swimming performance. Lower limbs action provided an important contribution in the energy availability in working muscles being advised its full use in this short duration and very high-intensity event.

     

Evaluation of an anorganic bovine-derived mineral with P-15 hydrogel bone graft: preliminary study in a rabbit cranial bone model

Objectives: The present investigation aimed to assess the bone‐regenerative potential of two formulations of anorganic bovine‐derived mineral bound to a P‐15 (ABM/P‐15) bone graft – the particulate and the hydrogel forms – in a delayed healing rabbit cranial defect model. Material and methods: Ten adult male New Zealand White rabbits were used to create two 8 mm transcortical cranial defects per rabbit and each one received randomly the test material (ABM/P‐15 carboxymethyl cellulose (CMC)‐hydrogel graft), the standard control material (ABM/P‐15 particulate graft) or remained empty as a negative control. The defects were allowed to heal for 2 and 4 weeks. Qualitative and quantitative histological outcomes were assessed on undecalcified sections. Results: In the defects grafted with the test material, at both time points, there was a marked random migration of the bone substitute particles. As a consequence, the space maintenance provision was lost and new bone formation was reduced compared with the control particulate graft material. The histomorphometric analysis showed that the control material attained better results, with an average of 13.8 ± 1.9% and 18.2 ± 4.4% of new bone at 2 and 4 weeks, compared with 8.5 ± 2.4% and 13 ± 2.9% for the test material. These differences were significant at 2 weeks (P≤0.05), but not at 4 weeks (P>0.05). Additionally, there was a significant difference in the total area of mineralized tissue (new bone plus particles), favoring the standard control over the test material: 43.2 ± 14.4% vs. 14.2 ± 5.3% at 2 weeks and 56.9 ± 4.2% vs. 24.2 ± 9.6% at 4 weeks, respectively. Conclusions: The test ABM/P‐15 CMC‐hydrogel graft material behaved in this animal model by migration of the graft particles, what determined an unpredictable osseoconduction and, consequently, a decreased quality and quantity of bone regeneration as compared with the osseopromotive behavior exhibited by the standard particulate form of the ABM/P‐15 control graft. It is therefore suggested to restrain the application of the hydrogel graft form in non‐contained anatomical bone defects.