Bottom Line Up Front (BLUF)
Core strength training was found to be an effective method to improve skiing economy in elite junior cross-country skiers by reducing the amount of energy needed to maintain performance during submaximal efforts. This study found that both static and dynamic core training programs led to significant improvements in energy efficiency, with a reduction in energetic cost by up to 4.1%. While static and dynamic core training yielded similar results, incorporating both types of exercises into training regimens can provide balanced gains in strength, stability, and functional movement.
Study Purpose
This study explored the impact of supplemental static and dynamic core strength training on skiing economy in elite junior cross-country (XC) skiers. The goal was to determine if core strength training improves the energy efficiency of skiers during submaximal efforts, potentially boosting performance.
Testing and Training Protocols
Participant Information:
- 24 elite junior XC skiers (14 women, 10 men; average age: 17.8 years).
Training Details:
Static Core Training (ST) Group:
- Exercises: Planks, side planks with arm/leg raises.
- Duration: 15 minutes, 3 sessions per week for 9 weeks.
- Progression: Gradual increase in difficulty, including removal of rest intervals and added loads (e.g., weight plates).
| Exercise | Sets | Duration/Load | Rest | Progression |
|---|---|---|---|---|
| Plank | 1 | 30 seconds | 15 sec | Gradually increased duration to 60 seconds. No rest between exercises in later stages. |
| Plank with Arm Raise | 1 | 30 seconds | 15 sec | Added external loads (weight plates) and reduced rest between exercises. |
| Plank with Leg Raise | 1 | 30 seconds | 15 sec | Progressed by incorporating alternating leg raises with external weights. |
| Plank with Alternating Leg and Arm Raise | 1 | 30 seconds | 15 sec | Progressed to no rest between exercises and added weights. |
| Side Plank | 1 | 30 seconds per side | 15 sec | Progressed to leg raised on a bench or elevated surface. |
| Side Plank with Leg Raise | 1 | 30 seconds per side | 15 sec | Progressed by adding external weights and performing with no rest between sets and exercises. |
Dynamic Core Training (DT) Group:
- Exercises: Dynamic movements such as glute bridges, unilateral squats, and V-ups.
- Duration: 15 minutes, 3 sessions per week for 9 weeks.
- Progression: Increased complexity with added weights, foam rollers, and higher reps.
| Exercise | Sets | Reps/Load | Rest | Progression |
|---|---|---|---|---|
| Lying Bent Knee Crunch (Yoga Mat Supported Lumbar Spine) | 3 | 10 reps | 30 sec | Added weight plates held with straight arms or alternated leg raises. |
| Glute Bridge with Leg Raise | 3 | 5 reps | 30 sec | Progressed to full leg raises and added rotational movements in later stages. |
| Side Bridge with One Leg Bent | 3 | 10 reps per side | 30 sec | Progressed to elevated surfaces and added external weights. |
| Unilateral Squat with Alternating Leg Forward/Backward | 3 | 10 reps per leg | 30 sec | Progressed to include forward and backward lunges and toe raises with external weights. |
Control Variables:
All participants maintained their regular endurance and strength training schedules, including:
- Four ski practice sessions per week.
- Two strength training sessions (circuit-based and hypertrophy training).
Testing Protocols:
- Energetic Cost Testing:
- Conducted on a roller ski treadmill at three submaximal workloads, increasing speed and elevation.
- Measurements: Oxygen consumption (VO₂), lactate levels, and heart rate.
- Maximal Incremental Testing:
- Roller ski treadmill test to measure VO₂max and peak heart rate.
Energetic Cost: What It Means and Results
What is Energetic Cost? Energetic cost measures how much energy (oxygen) your body uses to maintain a certain pace. In skiing, a lower energetic cost means you’re skiing more efficiently—expending less energy for the same effort.
Study Findings:
- After 9 weeks of core strength training, participants used less oxygen at the same skiing pace, improving their energy efficiency.
- Measured improvements at three effort levels (workloads):
- Low-intensity effort: Energetic cost reduced by 4.1%, meaning skiers became significantly more efficient during easier paces.
- High-intensity effort: Energetic cost reduced by 2.9%, showing smaller but still meaningful efficiency gains at harder paces.
Why This Matters:
- Improved energy efficiency helps skiers maintain their pace longer without tiring as quickly, which is critical for endurance events like cross-country skiing.
Key Results
- Energetic Cost (EC):
- Pooled data from both static and dynamic training groups showed significant reductions in energetic cost at all effort levels.
- Static training exhibited slightly larger improvements than dynamic training, though the differences were not statistically significant.
- VO₂max and Lactate Levels:
- No significant changes were observed in VO₂max or lactate levels, indicating the core training’s effects were specific to skiing economy rather than overall aerobic capacity.
- Dynamic Balance and Technique:
- Improvements in skiing economy suggest better core stability may reduce unnecessary movement, leading to smoother and more efficient skiing.
Key Takeaways for Coaches and Athletes
- Core Training Recommendations:
- Both static and dynamic core exercises enhance skiing economy. A balanced mix of these can target multiple aspects of strength and stability.
- Progression and consistency are key: Gradually increase the complexity and intensity of core training.
- Energetic Cost Reduction:
- Reducing energy use at submaximal efforts can help athletes sustain high performance in long events.
- Core strength contributes to improved posture, balance, and movement efficiency.
- Program Design:
- Include functional exercises that mimic skiing-specific movements (e.g., unilateral or rotational movements).
- Dedicate 15–20 minutes per session, 2-3 times per week, to structured core strength training.
Conclusion
This study highlights the value of core strength training in improving skiing economy for elite junior XC skiers and likely for all endurance-focused athletes. By reducing the energetic cost of movement, these interventions allow skiers to perform more efficiently during long races. While the study didn’t show significant differences between static and dynamic training, the overall takeaway is clear: incorporating core exercises into training routines is essential for performance enhancement.
Effects of Core Strength Training on Skiing Economy in Elite Junior Cross-Country Skiers, Therell, Jansson, Theos
Research Quarterly for Exercise & Sport