**3. Results**

**Figure 1** demonstrates multidirectional changes in the maximum peak power in drop jumps from different heights performed by the subjects. Mogul skiers showed negative dynamics of the maximum peak power as the height of the drop jump increased: the maximum peak power in drop jumps from the height of 0.1 m and 0.3 m differed by 2.67 ± 0.05 W/kg ((T = 0,0, p = 0,043), the difference of the maximum peak power in drop jumps from the height of 0.3 m and 0.5 m was 2.89 ± 0.07 W/kg (T = 0,0 p = 0,041). All the other subjects (alpine skiers, bobsledders, and ski jumpers) showed positive dynamics of maximum peak power. The greatest maximum peak power was reached in the group of ski

*Peculiarities of Muscle-Tendon Mechanics and Energetics in Elite Athletes in Various Sports DOI: http://dx.doi.org/10.5772/intechopen.97000*

**Figure 1.** *The maximum peak power in the take-off phase.*

jumpers (0.1 m – 59.2 ± 0.23 W/kg; 0.3 m – 62.8 ± 0.30; 0.5 m – 79.8 ± 0.56 W/kg), while the lowest – in the group of mogul skiers (0.1 m – 59.2 ± 0.27 W/kg; 0.3 м – 62.8 ± 0.23 W/kg; 0.5 м – 79.8 ± 0.46 W/kg) . Mogul skiers demonstrated significant difference in maximum peak power in comparison with the other athletes (H = 8,22003 p < 0,01).

Time of the take-off phase (**Figure 2**) significantly differs in ski jumpers (0,1 м - 0,18 ± 0,06 s; 0,3 м - 0,215 ± 0,05 s; T = 8,32117, p > 0,01; 0,5 м - 0,23 ± 0,07 s; T = 8,32117, p > 0,01) and in athletes from the other groups. The average time of the take-off in the groups of bobsledders, alpine skiers and mogul skiers was 0.11–0.13 ± 0.02 s in all jumps, while in ski jumpers it was 0.18–0.23 ± 0.05 s (H = 8,32117, p < 0,01).

If we compare **Figures 1** and **3**, we will note that the athletes achieved different power of movement on the background of different leg stiffness. The maximum leg stiffness was registered in alpine skiers in drop jumps from 0.1 m – 23659.6 ± 1182 N/m, bobsledders in drop jumps from 0.3 m – 24384,9 ± 987 N/m, and mogul skiers in drop jumps from 0.5 m - 23608,8 ± 1243 N/m; the minimal leg stiffness was registered in ski jumpers (0.1 m - 14463,4 ± 723 N/m; 0.3 m - 9206,8 ± 803 N/m and 0.5 m - 7115,1 ± 654 N/m). The difference between the groups was significant (H = 8.75356, p < 0.01), the dynamics of data within each group was different. Mogul skiers demonstrated the maximum values in leg stiffness in drop jumps from 0.5 m. In alpine skiers

**Figure 2.** *Time of the take-off phase.*

**Figure 3.** *Peak value of the stiffness of the muscles of the lower extremities in drop jumps.*

and ski jumpers the maximal leg stiffness was found in drop jumps from 0.1 m. The small height may permit these athletes to perform preliminary muscle stimulation before landing that makes it possible to counteract external inertial forces acting on the body. When the height is greater, athletes try to compensate loads on the musculoskeletal system in shock absorption phase by increasing the amplitude of movement in the knee joints, thereby reducing the stiffness of the legs. In bobsledders leg stiffness in the jump from 0.5 m was 6.5% lower than that in the jump from 0.3 m. It might be that the bobsledders tried to keep high leg stiffness, but as they were heavy, their muscles could not resist the load in the eccentric phase.

Energy transfer between the muscle groups of the lower extremities during the concentric contraction phase of the take-off was calculated using the method described in [4, 35] (**Figure 4**). We found that the mechanism of energy transfer was almost not used by ski jumpers (Hip-Knee: 3–6%, Knee-Ankle: less than 3%, H = 8,564 p < 0,01). The highest percentage of energy transfer was found in bobsledders (Knee-Ankle: 28 ± 0.8% in a drop jump from 0.3 m, 25 ± 0.7% in a drop jump from 0.5 м) and alpine skiers (Hip-Knee: 23 ± 0.4% from 0.3 м), but the segments

#### **Figure 4.**

*Transfer of energy between muscle groups of the lower limbs in the take-off phase (concentric muscle contraction).*

#### *Peculiarities of Muscle-Tendon Mechanics and Energetics in Elite Athletes in Various Sports DOI: http://dx.doi.org/10.5772/intechopen.97000*

of the lower limbs mostly involved in the energy transfer were different in those two groups. In bobsledders the highest energy transfer occurred from the thigh muscles to the lower leg muscles via the knee joint, while in alpine skiers energy transfer between the hip extensors and the thigh muscles was the highest. Mogul skiers showed a very low energy transfer from the hip extensors to the thigh muscles and almost no energy transfer from the thigh muscles to the lower leg muscles via the knee joint.

Gl - gluteus maximus, gluteus medius, gluteus minimus muscles, RF - rectus femoris, VAS - vastus medialis, GAS - lateral sections of the gastrocnemius muscle, SOL - soleus muscle.

The highest peak metabolic costs of all lower extremities muscles were found in mogul skiers (**Figure 5**). In all athletes peak metabolic costs of the hip extensor (Gl) tended to decrease, as the height of drop jumps increased, because athletes tried to maintain more upright posture for stability. All athletes had the lowest peak metabolic costs in GAS. In mogul skiers the maximum metabolic costs in GAS were registered in drop jumps from the height of 0.1 m (40.9 ± 2.5 W); in ski jumpers the minimum metabolic costs in GAS were registered in drop jumps from the height of 0.5 m (7.2 ± 1.2 W). High peak metabolic costs in RF and VAS were found in all athletes (87.2–73.1 and 105.1–74.6 W, correspondingly). As the height of drop jumps increased, the metabolic costs in RF and VAS\_L increased in mogul skiers and decreased in alpine skiers. The total metabolic costs increased in mogul skiers and ski jumpers, were stable in alpine skiers, and decreased in bobsledders, when the height of drop jumps increased.

Gl - gluteus maximus, gluteus medius, gluteus minimus muscles, RF - rectus femoris, VAS - vastus medialis, GAS - lateral sections of the gastrocnemius muscle, SOL - soleus muscle.

The peak force in the tendon of the MTU model involved in the take-off is shown in **Figure 6**. Ski jumpers had the lowest peak force in the tendon in comparison with the other subjects for all muscles and in all drop jumps. Alpine skiers, bobsledders and mogul skiers demonstrated active work in the tendons of the GAS and SOL muscles, as well as positive dynamics, as the height of drop jumps increased. Tendon activity of VAS in mogul skiers and alpine skiers revealed similarity in magnitude and positive dynamics. The greatest peak activity of the Gl tendons during the take-off was observed in alpine skiers when drop jumping from a height of 0.5 m (108.3 ± 6.7 N).

**Figure 5.** *Metabolic expenditures in simulated muscles.*

**Figure 6.** *Peak active tendon force.*
