Plyometric exercise enhances twitch contractile properties but fails to improve voluntary rate of torque development in highly trained sprint athletes

Purpose: The objective of this study was to evaluate a plyometric conditioning activity (3 sets of 5 countermovement jumps, [CA]) for twitch properties and voluntary knee extension. Methods: After a familiarization session, fourteen highly trained sprint athletes, 12 men (23.25 ± 7.17 years) and 2 women (23.0 ± 2.8 years) performed 2 experiments, each in a randomized order (crossover design). In one experiment, the time-course of twitch contractile properties was evaluated with and without the previous CA at 2, min intervals to 10 min of recovery. In the second session, maximal voluntary knee extension was evaluated at the same recovery intervals, for control and experimental condition in random order. Results: Mixed-model ANOVA with Bonferroni post-hoc revealed significant differences between pre-test and 2 min (p < 0.01, ES = 0.42) and 4 min (p < 0.01, ES = 0.20) for peak twitch torque of quadriceps femoris muscles confirming postactivation potentiation [PAP] at these times. Twitch rate of torque development (RTD) was significantly greater than pre-test value only at 2 min (p < 0.01, ES = 0.58) after the CA. Twitch contraction time and ½ relaxation time were not significantly difference from pre-test values after the CA (p > 0.05). No significant difference was observed for voluntary RTD following CA. Conclusion: The plyometric CA increased twitch peak torque and RTD consistent with PAP; however, there was no effect of CA on voluntary RTD of knee extension at any time after the plyometric CA. Even with PAP confirmed, we observed that the CA fails to improve isometric RTD of quadriceps femoris muscles. HighlightsA plyometric CA significantly increased twitch peak torque (at 2 and 4 min) and twitch rate of torque development (at 2 min) of quadriceps femoris muscles, indicating postactivation potentiation (PAP).No effect was observed for twitch contraction time and ½ relaxation time after the CA.No improvement was observed on voluntary rate of torque development evaluated at the same time intervals.

Does postactivation potentiation (PAP) increase voluntary performance?

The transient increase in torque of an electrically evoked twitch following a voluntary contraction is called postactivation potentiation (PAP). Phosphorylation of myosin regulatory light chains is the most accepted mechanism explaining the enhanced electrically evoked twitch torque. While many authors attribute voluntary postactivation performance enhancement (PAPE) to the positive effects of PAP, few actually confirmed that contraction was indeed potentiated using electrical stimulation (twitch response) at the time that PAPE was measured. Thus, this review aims to investigate if increases in voluntary performance after a conditioning contraction (CC) are related to the PAP phenomenon. For this, studies that confirmed the presence of PAP through an evoked response after a voluntary CC and concurrently evaluated PAPE were reviewed. Some studies reported increases in PAPE when PAP reaches extremely high values. However, PAPE has also been reported when PAP was not present, and unchanged/diminished performance has been identified when PAP was present. This range of observations demonstrates that mechanisms of PAPE are different from mechanisms of PAP. These mechanisms of PAPE still need to be understood and those studying PAPE should not assume that regulatory light chain phosphorylation is the mechanism for such enhanced voluntary performance. Novelty The occurrence of PAP does not necessarily mean that the voluntary performance will be improved. Improvement in voluntary performance is sometimes observed when the PAP level reaches extremely high values. Other mechanisms may be more relevant than that for PAP in the manifestation of acute increases in performance following a conditioning contraction.

[Ruptured splenic artery aneurysm--a rare cause of recurrent gastrointestinal hemorrhages]

HISTORY AND CLINICAL FINDINGS

A 51-year-old asthenic patient attended the hospital with syncope, head injury, tarry stool and severe anemia. There was a history of alcohol and nicotine abuse, but no known preceding diseases of the liver or gastrointestinal tract. Except hypotension, examination of the patient did not show any further abnormalities.

DIAGNOSTIC PROCEDURE

An upper and lower endoscopy did not show any evidence of a bleeding source although the stomach was full of hematin. An abdominal ultrasound demonstrated signs of a chronic pancreatitis and a big cystic structure in the area of the pancreatic tail. Pulsed and color Doppler imaging followed by angiography led to the diagnosis of a pseudoaneurysm of the splenic artery.

TREATMENT AND COURSE

After confirming the diagnosis, a laparotomy was performed. It revealed a pseudoaneurysm arising from the splenic artery that had penetrated the stomach and caused bleeding. Resection of the aneurysm, the stomach fundus, the left pancreas and the spleen was performed. 10 days after laparotomy, the patient was discharged from hospital in a good clinical condition.

CONCLUSION

Pseudoaneurysms of the splenic artery are an uncommon cause of gastrointestinal bleeding. The most important factor in detecting a pseudoaneurysm is considering the diagnosis. It is necessary to check for a pseudoaneurysm secondary to pancreatitis with pulsed or color Doppler imaging especially if a pseudocyst was first diagnosed with abdominal ultrasound. Because of the high mortality of a pseudoaneurysm, surgical resection or interventional radiology should be done as early as possible.

[Iliaco-ureteral fistula and its treatment with a stent graft]

The iliac artery-ureteral fistula is a rare complication which becomes symptomatic with life-endangering bleeding. A typical feature is its intermittent occlusion, which makes diagnosis very difficult. Without knowledge of the correct diagnosis the rate of morbidity, through functional loss of the kidneys, and of mortality can be extremely high. In the following a case is described in which, after radiotherapy and chemotherapy following sigmoid resection due to carcinoma, urinary congestion of the remaining functional kidney occurred during the course of treatment. Following the placing of an endoureteral stent an iliac-ureteral fistula with massive bleeding developed. It was demonstrated by means of angiography. For the first time, therapy with endoluminal stent grafts was successfully applied.

Technical failure of biliary metal stent deployment in a series of 116 applications

Biliary metal stents are thought to offer improved long-term palliation of malignant biliary obstruction due to a lower incidence of migration and clogging. Placement of these stents is technically more complicated than that of plastic endoprostheses and requires two experienced physicians. We report the incidence and reasons for apparent malfunction of expandable metal stent deployment (Wallstents and Strecker stents). In 116 applications of 82 Wallstents (endoscopic approach: n = 33, transhepatic approach: n = 49), we observed 19 cases of stent malfunction due to technical problems of stent delivery. In 13 cases (15.8%), the restraining membrane of the Wallstent could not be retracted sufficiently to deliver the stent. There were 6 (17.6%) failures in 34 cases of Strecker stent deployment. In 3 cases, we noted difficult balloon removal, including avulsion of the balloon catheter shaft within the endoscope during attempted balloon removal in one case. In one case, the Strecker stent could only be released partially, requiring subsequent endoscopic extraction. In two patients, only partial expansion of one end of the Strecker stent could be achieved. Given the significant malfunction rate of expandable metal stents during stent delivery, further improvements in the delivery system of the metal stents are required.

[Percutaneous, transrenal balloon catheter dilatation. A possibility for the treatment of uretero-enteral implantation stenoses]

In contrast to the undisputed position of percutaneous translumenal balloon catheter dilation of arteriostenoses, the use of this method on strictures of the efferent urinary tract is hardly known. Encouraged by initial promising reports, we present our own application of this method in a cases of bilateral recidive implantation stenoses with progressive hydronephrosis following operative revision of a Bricker conduit. Balloon dilation (Grüntzig catheter) was performed several times antegradely via previously made bilateral percutaneous pyelonephrostomies. The follow-up period was 12 months. Clinical consolidation of the patient's state with an initial unilateral morphological confirmation of improvement in the drainage of urine is an encouragement to repeat the procedure. If the late result is also good and when we have more experience, this method could be an acceptable alternative in the very difficult decision between terminal insertion of a pyelo-nephrostomy and the strain of a repeated reconstruction operation, especially in patients at high risk for operations or generally.

[Results of ligature of the upper testicular vein in idiopathic varicocele and subfertility]

The results of a total of 102 varicocele operations, 83 of which were performed because of subfertility and a desire to have children, are presented. In 3% of the cases a recidive operation was necessary because of persistent varicocele. 55 patients with limited fertility were subsequently examined for volume, density and form of sperm, total motility and propulsive motility. Whereas the volume of sperm and the total motility remained unchanged, the density and form of sperm and the propulsive motility had improved significantly 9 months after the operation. Among the men followed up the conception rate was 20%.

[Effect of portasystemic anastomoses in childhood on propranolol pharmacokinetics]

Kinetics of propranolol after oral administration were investigated in 9 children aged 5--11 years with intact liver function who had undergone porto-systemic anastomosis surgery for pylethrombosis and in a 16-year-old boy with a Warren shunt. Bioavailability of the drug had increased by twice the values measured in physiologic liver blood flow; elimination half-life had doubled. These alterations must be taken into consideration in medication, e.g. extreme care must be exercised in the oral administration of "first pass" drugs in porto-systemic shunt patients and it is recommended that the initial dose should be at the level of intravenous administration. The reduced rate of elimination should be taken into account in the case of drugs whose elimination depends on liver blood flow.

[Kidney circulation in chronic parenchyma diseases and in kidney insufficiency]

In 38 patients with glomerulo- (20 patients) and pyelonephritis the renal blood flow was measured with radioxenon. Despite normal creatinine clearance in chronic diseases the blood flow is already reduced. The correlation to the creatinine clearance is loose. In glomerulonephritis above all a reduction of the blood flow of the cortex appears, in pyelonephritis the participation of the cortex is reduced. Correlations of blood circulation and blood pressure are to be found in no stage of the disease. Concerning the renal insufficienzy there does not exist a disease-specific pattern of blood flow. In renal insufficiency the diuresis is independent of blood flow.