Botulinum toxin as a treatment for functional popliteal artery entrapment syndrome.

PURPOSE: Functional popliteal artery entrapment syndrome is responsible for exercise-induced muscle leg pain. This syndrome is caused, in most of the cases, by the excessive size of the gastrocnemius muscles. Currently, its treatment is based only on surgery with variable results. METHODS: We report the case of a young professional soldier in a combat unit with bilateral functional popliteal artery entrapment syndrome that was confirmed by dynamic arteriography, magnetic resonance angiography, and ultrasonography and did not improve after bilateral popliteal arteriolysis without resection of the gastrocnemius medial head. Treatment by injecting botulinum toxin in the proximal part of the gastrocnemius muscles was proposed and carried out. RESULTS: Regular follow-up (from 1 month to 3 yr after botulinum toxin treatment) showed the disappearance of exercise-induced pain and the improvement of the patient's physical and sports performance. Results of follow-up ultrasonography during dynamic maneuvers at 2.5 months and 2 yr after botulinum toxin injection were normal. Neither adverse effects nor motor deficit of the gastrocnemius muscles was reported. CONCLUSIONS: This case report suggests that botulinum toxin treatment could be an alternative to surgery for patients with functional popliteal artery entrapment syndrome. Botulinum toxin could reduce functional compression and, consequently, exercise-induced pain by decreasing the volume of the gastrocnemius muscle.

Effect of eccentric versus concentric exercise training on mitochondrial function.

INTRODUCTION: The effect of eccentric (ECC) versus concentric (CON) training on metabolic properties in skeletal muscle is understood poorly. We determined the responses in oxidative capacity and mitochondrial H2 O2 production after eccentric (ECC) versus concentric (CON) training performed at similar mechanical power. METHODS: Forty-eight rats performed 5- or 20-day eccentric (ECC) or concentric (CON) training programs. Mitochondrial respiration, H2 O2 production, citrate synthase activity (CS), and skeletal muscle damage were assessed in gastrocnemius (GAS), soleus (SOL) and vastus intermedius (VI) muscles. RESULTS: Maximal mitochondrial respiration improved only after 20 days of concentric (CON) training in GAS and SOL. H2 O2 production increased specifically after 20 days of eccentric ECC training in VI. Skeletal muscle damage occurred transiently in VI after 5 days of ECC training. CONCLUSIONS: Twenty days of ECC versus CON training performed at similar mechanical power output do not increase skeletal muscle oxidative capacities, but it elevates mitochondrial H2 O2 production in VI, presumably linked to transient muscle damage.

Eccentric exercise training: modalities, applications and perspectives.

Eccentric (ECC) exercise is classically used to improve muscle strength and power in healthy subjects and athletes. Due to its specific physiological and mechanical properties, there is an increasing interest in employing ECC muscle work for rehabilitation and clinical purposes. Nowadays, ECC muscle actions can be generated using various exercise modalities that target small or large muscle masses with minimal or no muscle damage or pain. The most interesting feature of ECC muscle actions is to combine high muscle force with a low energy cost (typically 4- to 5-times lower than concentric muscle work) when measured during leg cycle ergometry at a similar mechanical power output. Therefore, if caution is taken to minimize the occurrence of muscle damage, ECC muscle exercise can be proposed not only to athletes and healthy subjects, but also to individuals with moderately to severely limited exercise capacity, with the ultimate goal being to improve their functional capacity and quality of life. The first part of this review article describes the available exercise modalities to generate ECC muscle work, including strength and conditioning exercises using the body's weight and/or additional external loads, classical isotonic or isokinetic exercises and, in addition, the oldest and newest specifically designed ECC ergometers. The second part highlights the physiological and mechanical properties of ECC muscle actions, such as the well-known higher muscle force-generating capacity and also the often overlooked specific cardiovascular and metabolic responses. This point is particularly emphasized by comparing ECC and concentric muscle work performed at similar mechanical (i.e., cycling mechanical power) or metabolic power (i.e., oxygen uptake, VO2). In particular, at a similar mechanical power, ECC muscle work induces lower metabolic and cardiovascular responses than concentric muscle work. However, when both exercise modes are performed at a similar level of VO2, a greater cardiovascular stress is observed during ECC muscle work. This observation underlines the need of cautious interpretation of the heart rate values for training load management because the same training heart rate actually elicits a lower VO2 in ECC muscle work than in concentric muscle work. The last part of this article reviews the documented applications of ECC exercise training and, when possible, presents information on single-joint movement training and cycling or running training programs, respectively. The available knowledge is then summarized according to the specific training objectives including performance improvement for healthy subjects and athletes, and prevention of and/or rehabilitation after injury. The final part of the article also details the current knowledge on the effects of ECC exercise training in elderly populations and in patients with chronic cardiac, respiratory, metabolic or neurological disease, as well as cancer. In conclusion, ECC exercise is a promising training modality with many different domains of application. However, more research work is needed to better understand how the neuromuscular system adapts to ECC exercise training in order to optimize and better individualize future ECC training strategies.