rhabdomyolysis is a clinical syndrome characterized by muscle necrosis and the release of intracellular muscle constituents into the circulation .
it can be caused by burns , shock , acidosis , infections , crush trauma , immobility , malignancy , toxins , drugs , and muscle diseases1 ) . among the various types of rhabdomyolysis ,
non - traumatic exertional rhabdomyolysis ( exrml ) occurs in individuals with normal muscles and appears when the energy supplied to the muscle is insufficient23 ) .
exrml related to military training , marathon running , weight training , and other forms of strenuous exercise have been reported4 ) .
spinning is a group indoor cycling exercise , which has become popular recently over the past few years .
this stationary cycling program is composed of five core movements and riders may synchronize their pedaling to the rhythm of the music while they are exercising5 ) .
we observed that recently there has been an increasing number of patients who were diagnosed with exrml at cha bundang medical center after attending a spinning class . here , we introduced the clinical cases of spinning induced rhabdomyolysis and review the related literature .
we found 11 cases of exrml patients who were admitted to cha bundang medical center between july 1 , 2014 and march 31 , 2015 .
their mean body mass index ( bmi ) was 23.92.6 kg / m ( ranged from 19.6 to 28.0 ) .
two to three days prior to the presentation , the patients had attended a spinning class for the first time .
nine of the patients had brown - colored urine within two days and another two patients noticed that their urine had become darker three days after their first spinning class .
none of the patients had any significant past medical history and were not on any medication .
their thighs were moderately firm and warm to the touch , with reduced range of movement and strength .
complete blood - count , urea , creatinine , and electrolyte values were within normal ranges at the initial blood analysis . however , their serum creatinine phosphokinase ( cpk ) level was over 11,000 u / l ( normal range : 38 - 160 ) . additionally , other serum levels of muscle enzymes ( creatine kinase - mb type , lactate dehydrogenase , alanine aminotransferase , aspartate aminotransferase , and myoglobin ) were significantly elevated ( table 1 ) .
serum bun and creatinine levels stayed within the normal range and no acute kidney injury ( aki ) had developed during treatment .
dipstick testing of the urine was positive ( 3 + ) for blood ; however , subsequent microscopy revealed less than four red blood cells under high power field ( hpf ) microscopy .
a bone scan study showed diffuse type of soft tissue uptakes in the damaged muscles including rectus femoris , sartorius , vastus medialis , vastus lateralis , and pectineus ( fig .
a diagnosis of rhabdomyolysis was made and the patients were treated with a combination of bed rest and aggressive intravenous fluid ( normal saline ) to maintain a urine output of 200 to 300ml / hour .
when the urine ph was less than 6.0 , sodium bicarbonate ( mixed with 5% dextrose water ) was used for urine akalinization .
although eight of the patients had mild hypocalcemia , calcium supplementation was unnecessary because no hypocalcemic symptoms were observed ( table 1 ) . in a span of 6 - 12 days ,
one patient ( number 1 ) was hospitalized for an additional 4 days after her cpk level was markedly reduced ( 4,820 u / l ) on the 8 day along with her complaints of thigh myalgia .
exrml has been defined by a combination of findings , including exercise - associated muscle pain , swelling , dark urine , and increased cpk level to at least five times the upper limit of normal , and myoglobinuria6 ) .
it should be noted that our patients had cpk levels of nearly 70 times the upper limit of normal ( table 1 ) .
also , a urine dipstick that is positive for blood but shows few red blood cells is suggestive of myoglobinuria7 ) . in the pathogenesis of exercise - induced rhabdomyolysis , calcium(ca ) has been suggested as an important key factor3 ) . during exercise ,
a decreased amount of adenosine triphosphate ( atp ) could cause dysfunction of na - k atpase and an increased level of na in the cells , resulting in the reverse activation of na - ca exchanger mode3 ) .
consequently , the increased intracellular calcium leads to the activation of proteases , skeletal muscle cell contraction , mitochondrial dysfunction , reactive oxygen species production , and eventual skeletal muscle cell death23 ) .
treatment of rhabdomyolysis involves stopping the continued breakdown of the muscle fibers and preventing the development of aki .
the rapid and aggressive infusion of intravenous crystalloid is used to obtain a urinary output of 200 - 300ml / hour .
myoglobin is toxic in acidic urine , and most experts advocate the use of intravenous sodium bicarbonate to maintain a urinary ph of 6.5 or greater67 ) .
loop diuretics may be given to patients who develop volume overload complications such as pulmonary edema .
the initiation of renal replacement therapy in clinical practice depends on the status of renal impairment , with complications such as life - threatening hyperkalemia , anuria , metabolic acidosis , or hyperhydration without response to diuretic therapy89 ) .
it is reported that both continuous venovenous hemofiltration with a high permeability membrane and high cutoff membrane hemodiafiltration are effective in removing serum myoglobin ( 17kda)1011 ) .
although successful treatment with plasmapheresis to remove serum myoglobin in statin - induced rhabdomyolysis have been reported , its use seems still controversial9 ) .
most of the related articles mentioned that the majority of spinning - induced rhabdomyolysis patients were discharged without any complication when they were treated early and aggressively with intravenous fluids7 ) . however , in rare cases , some patients demonstrated severe complications , such as compartment syndrome and aki4 ) .
aki in rhabdomyolysis may occur due to renal vasoconstriction , formation of intratubular casts , and direct myoglobin toxicity caused by accumulation of myoglobin in the renal tubules19 ) .
compartment syndrome may occur in the leg or forearm due to the edema caused by muscle injury and tissue damage4 ) .
cardiac dysrhythmias via electrolyte abnormalities and disseminated intravascular coagulopathy are other possible complications of exrml4 ) .
known risk factors of exrml are the exercise experience , intensities or types of exercises37 ) .
other possible causes were hyperthermal environments , electrolyte imbalance , malnutrition , creatine supplements and alcohol drinking3 ) .
influenza virus infection and genetic deficiency of metabolic factors can be risk factors as well3 ) .
it has been reported that men are vulnerable to exrml because estrogen plays a protective role1213 ) .
interestingly , all 11 spinning - induced rhabdomyolysis cases in this article occurred in females .
it is unclear whether they were malnourished by their diet plan or had little exercise experience and thus were at higher risk of spinning induced rhabdomyolysis .
third , exercise should be modified or abstained in the presence of evitable risk factors such as influenza .
all 11 patients were treated early and properly without any complication , except a mild non - symptomatic hypocalcemia . however , considering the possibility of severe complications of exrml as aforementioned , and the medical expenses of hospital stay , information and guidelines for preventing spinning - induced rhabdomyolysis have to be provided prior to starting the exercise .
 non - traumatic exertional rhabdomyolysis ( exrml ) occurs in individuals with normal muscles when the energy supplied to the muscle is insufficient . here 
 , we report 11 cases of spinning - induced rhabdomyolysis and review related literature . 
 spinning is a kind of indoor bicycle sport . 
 the 11 patients who were diagnosed with exrml and admitted to cha bundang medical center were female and their ages ranged from 15 to 46 years . 
 two to three days prior to the presentation , the patients had attended a spinning class for the first time . 
 all the patients had been otherwise healthy without any known medical illnesses . 
 they were successfully treated without any complications , except mild non - symptomatic hypocalcemia . however , in the literature , severe complications such as compartment syndrome or acute kidney injury had been reported in relation to exrml including spinning - induced rhabdomyolysis . 
 this spinning exercise needs prior guidelines and specific warnings to prevent exertional rhabdomyolysis . 
Introduction
Case Report
Discussion