The Effect of Training in the Preparatory and Competitive Periods on Trunk Rotational Power in Canoeists, Ice-Hockey Players, and Tennis Players

Strength and Power-Related Measures in Assessing Core Muscle Performance in Sport and Rehabilitation

While force-velocity-power characteristics of resistance exercises, such as bench presses and squats, have been well documented, little attention has been paid to load, force, and power-velocity relationships in exercises engaging core muscles. Given that power produced during lifting tasks or trunk rotations plays an important role in most sport-specific and daily life activities, its measurement should represent an important part of the test battery in both athletes and the general population. The aim of this scoping review was 1) to map the literature related to testing methods assessing core muscle strength and stability in sport and rehabilitation, chiefly studies with particular focus on force-velocity-power characteristics of exercises involving the use of core muscles, 2) and to identify gaps in existing studies and suggest further research in this field. The literature search was conducted on Cochrane Library databases, Scopus, Web of Science, PubMed and MEDLINE, which was completed by SpringerLink, Google Scholar and Elsevier. The inclusion criteria were met in 37 articles. Results revealed that among a variety of studies investigating the core stability and core strength in sport and rehabilitation, only few of them analyzed force-velocity-power characteristics of exercises involving the use of core muscles. Most of them evaluated maximal isometric strength of the core and its endurance. However, there are some studies that assessed muscle power during lifting tasks at different loads performed either with free weights or using the Smith machine. Similarly, power and velocity were assessed during trunk rotations performed with different weights when standing or sitting. Nevertheless, there is still scant research investigating the power-velocity and force-velocity relationship during exercises engaging core muscles in able-bodied and para athletes with different demands on stability and strength of the core. Therefore, more research is needed to address this gap in the literature and aim research at assessing strength and power-related measures within cross-sectional and intervention studies. A better understanding of the power-force-velocity profiles during exercises with high demands on the core musculature has implications for designing sport training and rehabilitation programs for enhancement of athletes' performance and/or decrease their risk of back pain.

Sport-Specific Differences in Power–Velocity–Force Profiling during Trunk Rotations at Different Loads

This study investigates differences in power and velocity at different loads and power and force at different velocities during trunk rotations in athletes who practice sports with rotational demands on the trunk. Athletes of combat (n = 23), fighting (n = 39), ball (n = 52) and water sports (n = 19) with a mean age of 23.8 ± 1.5 years performed standing trunk rotations on each side with bars of different weights (from 1 kg up to 50 kg) placed on their shoulders. The findings showed significant between-group differences in mean power in the acceleration phase of trunk rotations, especially at higher weights (≥10.5 kg) or lower velocities (≤334.2 rad/s). The power at 10.5 kg was significantly higher in fighting than water (p = 0.035; d = 0.86), combat (p = 0.001; d = 1.53) and ball sports athletes (p = 0.001; d = 1.48), with no significant differences between the two latter groups; at 15.5 kg, it was higher in water than combat (p = 0.027; d = 0.91) and ball sports athletes (p = 0.009; d = 1.17) but not those in fighting sports; and at 20 kg, it was higher in water than combat (p = 0.013; d = 0.98) and ball sports athletes (p = 0.006; d = 1.33), with no significant differences with those in fighting sports. This testing is sensitive in discriminating between athletes of various sports, which may reflect the specificity of their training, including trunk rotations at various velocities under different load conditions.

Is There a Relationship Between Workload and Occurrence of Back Pain and Back Injuries in Athletes?

The back is subjected to a great deal of strain in many sports. Up to 20% of all sports injuries involve an injury to the lower back or neck. Repetitive or high impact loads (e.g., running, gymnastics, skiing) and weight loading (e.g., weightlifting) affect the lower back. Rotation of the torso (e.g., golf, tennis) causes damage to both, the lumbar and thoracic spine. The cervical spine is most commonly injured in contact sports (e.g., boxing, football). One of the factors that increases the odds of injuries in athletes is excessive and rapid increases in training loads. In spite of currently emerging evidence on this issue, little is known about the balance between physiological loading on the spine and athletic performance, versus overloading and back pain and/or injury in athletes. This scoping review aims (i) to map the literature that addresses the association between the training load and the occurrence of back pain and/or injury, especially between the Acute:Chronic Workload Ratio (ACWR) and back problems in athletes of individual and team sports, and (ii) to identify gaps in existing literature and propose future research on this topic. A literature search of six electronic databases (i.e., MEDLINE, PubMed, Web of Science, SCOPUS, SportDiscus, and CINAHL) was conducted. A total of 48 research articles met the inclusion criteria. Findings identified that fatigue of the trunk muscles induced by excessive loading of the spine is one of the sources of back problems in athletes. In particular, high training volume and repetitive motions are responsible for the high prevalence rates. The most influential are biomechanical and physiological variations underlying the spine, though stress-related psychological factors should also be considered. However, limited evidence exists on the relationship between the ACWR and back pain or non-contact back injuries in athletes from individual and team sports. This may be due to insufficiently specified the acute and chronic time window that varies according to sport-specific schedule of competition and training. More research is therefore warranted to elucidate whether ACWR, among other factors, is able to identify workloads that could increase the risk of back problems in athletes.

Between-side differences in trunk rotational power in athletes trained in asymmetric sports

BACKGROUND

The asymmetric loading of trunk muscles in sports like golf or tennis may cause side-to-side imbalances in rotational muscle strength and endurance. Such imbalances may be compounded by the presence of low back pain (LBP) and related injuries. However, trunk rotational power is a better predictor of athlete performance, and therefore its ability to reveal these asymmetries/dysbalances should be investigated.

OBJECTIVE

This study compares peak and mean values of power during trunk rotations on the dominant and non-dominant side in golfers, ice-hockey players, tennis players, and an age-matched control group of fit individuals.

METHODS

Groups of 17 golfers, 17 ice-hockey players, 21 tennis players, and 39 fit individuals performed standing trunk rotations to each side with a bar weight of 5.5, 10.5, 15.5, and 20 kg placed on the shoulders. Peak power and mean power in the acceleration phase of trunk rotations were measured using the FiTRO Torso Premium system.

RESULTS

Peak power and mean power in the acceleration phase of trunk rotations were significantly higher on the dominant (D) than non-dominant (ND) side at weights of 5.5 kg (14 and 14%), 10.5 kg (17 and 14%), 15.5 kg (16 and 15%), and 20 kg (16 and 16%) in ice-hockey players, at 5.5 kg (14 and 13%), 10.5 kg (17 and 14%), and 15.5 kg (15% - only peak power) in tennis players, and at 5.5 kg (17 and 18%) and 10.5 kg (19 and 17%) in golfers. However, their values did not differ significantly at these weights (< 10%) in the age-matched control group. The D/ND ratio was the highest in ice-hockey players (1.18, 1.19), followed by golfers (1.16, 1.17) and finally tennis players (1.12, 1.16).

CONCLUSION

Taking into account significantly higher trunk rotational power on the dominant than the non-dominant side in golfers, tennis players and ice-hockey players at lower and/or higher weights and no significant side-to-side differences in a control group of fit individuals, this parameter may be considered specific to their asymmetric loading during trunk rotations. However, whether these asymmetries/dysbalances expressed by the D/ND ratio could also identify the likelihood of LBP, needs to be proven.