Fatigue-Induced Balance Impairment in Young Soccer Players

Context:

Although balance is generally recognized to be an important feature in ensuring good performance in soccer, its link with functional performance remains mostly unexplored, especially in young athletes.

Objective:

To investigate changes in balance induced by fatigue for unipedal and bipedal static stances in young soccer players.

Design:

Crossover study.

Setting:

Biomechanics laboratory and outdoor soccer field.

Patients or Other Participants:

Twenty-one male soccer players (age = 14.5 ± 0.2 years, height = 164.5 ± 5.6 cm, mass = 56.8 ± 6.8 kg).

Intervention(s):

Static balance was assessed with postural-sway analysis in unipedal and bipedal upright stance before and after a fatigue protocol consisting of a repeated sprint ability (RSA) test (2 × 15-m shuttle sprint interspersed with 20 seconds of passive recovery, repeated 6 times).

Main Outcome Measure(s):

On the basis of the center-of-pressure (COP) time series acquired during the experimental tests, we measured sway area, COP path length, and COP maximum displacement and velocity in the anteroposterior and mediolateral directions.

Results:

Fatigue increased all sway values in bipedal stance and all values except COP velocity in the mediolateral direction in unipedal stance. Fatigue index (calculated on the basis of RSA performance) was positively correlated with fatigue/rest sway ratio for COP path length and COP velocity in the anteroposterior and mediolateral directions for nondominant single-legged stance.

Conclusions:

Fatigued players exhibited reduced performance of the postural-control system. Participants with better performance in the RSA test appeared less affected by balance impairment, especially in single-legged stance.Key Words: postural sway, repeated sprint ability test, athletes

Key Points

• In young soccer players, balance was adversely affected by fatigue.
• A moderate correlation existed between balance impairment and repeated sprint ability performance.

In soccer, as in many other disciplines, researchers continuously attempt to define which anthropometric, physiologic, psychological, and cognitive characteristics are most relevant to identifying talent at an early age. Such features, together with the development of new assessment methods in the laboratory or on the field, are essential to improving the chances of recognizing future top players.In particular, somatotype, aerobic and anaerobic power, agility, joint flexibility, and muscular development are considered essential contributors to achieving high-level performance.¹ Nevertheless, it remains unclear how these factors are to be objectively selected, measured, weighed, and combined with coaches'' subjective perceptions, which are mainly based on personal experience.^1,2Somewhat surprisingly, balance is not included among the most important features in athletic success; this quality is considered important mostly as a cofactor that helps reduce the risk of injuries.³ Also, soccer is a discipline that relies a great deal on single-legged support under unstable conditions. In fact, players use 1 limb (the dominant limb) to control the force and direction of the ball while dribbling, maintaining ball possession, and kicking; the nondominant limb basically ensures the necessary stability to optimally perform the required technical maneuver.⁴ Thus, it appears very important for players to have (and possibly improve during their maturation) excellent balance skills, especially for unipedal stance.Although previous authors^5–7 have shown that soccer players are generally characterized by superior balance performance compared with athletes in other sports (except gymnasts) or nonathletes, few data are available on the relationship between balance variables and functional performance in soccer players.⁸ Similarly, the possibility of improving postural-control performance in healthy athletes using specific balance-training protocols remains partly unexplored. However, recent investigators^9,10 have demonstrated that young athletes may benefit from proper stimulation of the proprioceptive system.

Balance and Fatigue

Both localized and whole-body fatigue cause degradation of postural-control performance, which is evident in the form of increased postural sway (ie, constant, slight corrective deviations from vertical when standing upright).¹¹ This phenomenon, which has been extensively reported in the literature, is mainly due to changes in cardiac and respiratory contractions, fluid movement in the body, and release of metabolic products by muscle fibers and is caused by altered sensory information from the proprioceptive system.¹² The magnitude of sway increase is partly influenced by exercise intensity and duration, but it also depends on the muscular groups involved.¹³ From this point of view, localized fatigue and whole-body fatigue are thought to trigger different disturbances of the postural-control system,¹⁴ although the net effect in terms of balance impairment may appear similar.Typical experiments aimed at assessing the effect of fatigue on static balance involve exercise such as the treadmill,^15–17 cycle or rowing ergometer,^14,15,18 isokinetic concentric actions, squat jumps, and heel raises.^14,19 A few authors^20,21 have evaluated the fatiguing effects of actual sport performance in triathletes²² and soccer players. In particular, Zemkova and Hamar²⁰ and Brito et al²¹ analyzed center-of-pressure (COP) velocity of 19- to 21-year-old players (unipedal and bipedal stances with eyes open or closed) before a game, in the break period between the first and second halves, and after a game. When visual input was present, single-legged balance was reduced after the match. Less evident was the effect of fatigue on bipedal standing: changes were observed only when the support surface was unstable and visual input suppressed.The lack of experimental data regarding the effects of fatigue on balance in soccer players is somewhat surprising, considering that fatigue is implicated in injury occurrence²³ and that a deficit in postural control may increase the risk of ankle injuries.²⁴ Thus, it is reasonable to hypothesize that not only may fatigue associated with performance in a match impair balance (and thereby increase the risk of injuries) but also that superior physical fitness in better-trained athletes may limit this effect.Our goal was to assess postural-sway changes induced by fatigue subsequent to a controlled field test (repeated sprint ability [RSA]) representative of actual soccer activity in a cohort of young elite soccer players. We had 2 questions: (1) Is unipedal and bipedal static balance impaired by fatigue? (2) Is there a functional relationship between performance level in RSA and balance alterations?     

Stiff left atrial syndrome after low‐dose radiotherapy for right breast cancer: The need for invasive hemodynamics at exercise

Stiff left atrial (LA) syndrome is a distinct phenotype of heart failure with preserved ejection fraction, characterized by predominant high LA pressure. We describe the case of a middle‐aged woman who developed exertional breathlessness during low‐dose radiotherapy for right breast cancer and who was eventually found to be affected by stiff LA syndrome. Invasive hemodynamics allowed the recognition of pathognomonic tall V waves in the wedge position during exercise, in spite of inconclusive noninvasive investigations.     

Ambulatory blood pressure monitoring over 24 h: A Latin American Society of Hypertension position paper—accessibility,clinical use and cost effectiveness of ABPM in Latin America in year 2020

Accurate office blood pressure measurement remains crucial in the diagnosis and management of hypertension worldwide, including Latin America (LA). Office blood pressure (OBP) measurement is still the leading technique in LA for screening and diagnosis of hypertension, monitoring of treatment, and long‐term follow‐up. Despite this, due to the increasing awareness of the limitations affecting OBP and to the accumulating evidence on the importance of ambulatory BP monitoring (ABPM), as a complement of OBP in the clinical approach to the hypertensive patient, a progressively greater attention has been paid worldwide to the information on daytime and nighttime BP patterns offered by 24‐h ABPM in the diagnostic, prognostic, and therapeutic management of hypertension. In LA countries, most of the Scientific Societies of Hypertension and/or Cardiology have issued guidelines for hypertension care, and most of them include a special section on ABPM. Also, full guidelines on ABPM are available. However, despite the available evidence on the advantages of ABPM for the diagnosis and management of hypertension in LA, availability of ABPM is often restricted to cities with large population, and access to this technology by lower‐income patients is sometimes limited by its excessive cost. The authors hope that this document might stimulate health authorities in each LA Country, as well as in other countries in the world, to regulate ABPM access and to widen the range of patients able to access the benefits of this technique.     

From short‐term blood pressure variability to atherosclerosis: Relative roles of vascular stiffness and endothelial dysfunction

Both arterial blood pressure (BP) average levels and short‐term BP variability (BPV) relate to hypertension‐mediated organ damage, in particular increased carotid artery intima‐media thickness (IMT) and carotid‐femoral pulse wave velocity (PWV). Endothelial dysfunction possibly mediates such damage. The authors aimed at further investigating such role in hypertensive patients. In 189 recently diagnosed, untreated hypertensive patients the authors evaluated, in a cross‐sectional design, the relationships of BP average levels and short‐term systolic (S) BPV (standard deviation of awake SBP or of 24‐hour‐weighted SBP) with IMT and PWV, and how much these relationships are explained by endothelial function parameters—brachial artery flow‐mediated dilation (FMD) and digital reactive hyperemia index (RHI). Multivariable models assessed the strength of these relationships to derive a plausible pathogenetic sequence. Both average SBP values and our measures of SBPV were significantly related to IMT (24‐hour mean SBP: r = .156, P = .034; 24‐hour‐weighted SBPV: r = .157, P = .033) and to PWV (24‐hour mean SBP: r = .179, P = .015; 24‐hour‐weighted SBPV: r = .175; P = .018), but only poorly related to FMD or RHI (P > .05 for all). At univariable regression analysis, FMD and RHI were both related to IMT, (P < .001), but not to PWV. When FMD and RHI were added to average SBP and SBPV parameters in a multivariable model, both significantly (P < .005) contributed to predict IMT, but not PWV. Thus, endothelial dysfunction relates to IMT independently of BP parameters, but appears to play a minor role in the association between BP variability‐related variables and arterial stiffening.     

High prevalence of serum antibodies reacting with simian virus 40 capsid protein mimotopes in patients affected by malignant pleural mesothelioma

Human malignant pleural mesothelioma (MPM) is considered a rare tumor, but recent estimations indicate that one-quarter million people will die of this neoplasm in Europe in the next three decades. The mineral asbestos is considered the main causative agent of this neoplasm. MPM is largely unresponsive to conventional chemotherapy/radiotherapy. In addition to asbestos exposure, genetic predisposition to asbestos carcinogenesis and to simian virus (SV)40 infection has also been suggested. SV40 is a DNA tumor virus found in some studies to be associated at high prevalence with MPM. SV40 sequences have also been detected, although at a lower prevalence than in MPM, in blood specimens from healthy donors. However, some studies have failed to reveal SV40 footprints in MPM and its association with this neoplasm. These conflicting results indicate the need for further investigations with new approaches. We report on the presence of antibodies in serum samples from patients affected by MPM that specifically react with two different SV40 mimotopes. The two SV40 peptides used in indirect ELISAs correspond to viral capsid proteins. ELISA with the two SV40 mimotopes gave overlapping results. Our data indicate that in serum samples from MPM-affected patients (n = 97), the prevalence of antibodies against SV40 viral capsid protein antigens is significantly higher (26%, P = 0.043) than in the control group (15%) represented by healthy subjects (n = 168) with the same median age (66 y) and sex. Our results suggest that SV40 is associated with a subset of MPM and circulates in humans.