Fredrick C. Hagerman

Fiber type composition of the vastus lateralis muscle of young men and women.

SUMMARY This study presents data collected over the past 10 years on the muscle fiber type composition of the vastus lateralis muscle of young men and women. Biopsies were taken from the vastus lateralis muscle of 55 women (21.2 ± 2.2 yr) and 95 men (21.5 ± 2.4 yr) who had volunteered to participate in various research projects. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were classified using mATPase histochemistry, and cross-sectional area was measured for the major fiber types (I, IIA, and IIB). Myosin heavy chain (MHC) content was determined electrophoretically on all of the samples from the men and on 26 samples from the women. With the exception of fiber Type IC, no significant differences were found between men and women for muscle fiber type distribution. The vastus lateralis muscle of both the men and women contained approximately 41% I, 1% IC, 1% IIC, 31% IIA, 6% IIAB, and 20% IIB. However, the cross-sectional area of all three major fiber types was larger for the men compared to the women. In addition, the Type IIA fibers were the largest for the men, whereas the Type I fibers tended to be the largest for the women. Therefore, gender differences were found with regard to the area occupied by each specific fiber type: IIA>I>IIB for the men and I>IIA>IIB for the women. These data establish normative values for the mATPase-based fiber type distribution and sizes in untrained young men and women.

Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women

SummaryTwenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6–8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p<0.05), and an increase in lean body mass (p<0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (1, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types 1, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.

Muscle fiber necrosis associated with human marathon runners

This study describes the events occurring in exercise-induced muscular necrosis. Biopsies of the gastrocnemius muscles of volunteer human marathon runners were extracted prior to and at intervals for 7 days following a marathon, and investigated ultrastructurally. Most of the preparations, including the pre-marathon samples, showed evidence of muscle fiber necrosis and inflammation. These preparations had many mitochondria, erythrocytes, leukocytes and other phagocytic cells within the extracellular and extravascular spaces. Less frequently observed were Z-line streaming and degeneration, contracture knots, disrupted sarcolemma, presence of erythrocytes within the muscle fibers, and empty basal lamina tubes in which the contents of the fibers and the sarcolemma had broken down to leave only the basal lamina outlining the former fiber. These abnormal conditions were most prevalent at 1 and 3 days after the marathon. These ultrastructural changes are compared and correlated with the reports of clinical manifestations of rhabdomyolysis and myoglobinuria. Because the abnormalities persist for the 7 day duration of these observations, and because many of these were observed in the pre-marathon biopsies, we conclude that both the intensive training for, and the marathon itself, induce inflammation and fiber necrosis which are manifested in the clinical symptoms for rhabdomyolysis and myoglobinuria. The inflammatory reaction that accompanies these activities may be a major factor in post-exercise soreness. The combined influences of training and necrosis are discussed in relation to muscle fiber type compositions of endurance athletes.

The effects of short-term resistance training on endocrine function in men and women

This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group (squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5 min post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol (CORT) and growth hormone (GH). Serum TT concentrations were significantly (P ≤ 0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations. Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3 when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all training phases but no significant differences were observed with training. These data illustrate that untrained individuals may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive in the early phase of strength adaptations with resistance training.

Applied Physiology of Rowing

SummaryElite oarsmen and oarswomen possess large body dimensions and show outstadning aerobic and anaerobic qualities. Oarsmen have V̇O2max values of 6.1 ± 0.6 L/min and have incurred O2 debts of between 10 and 20 litres. The caloric expenditure of rowing estimated from the O2 cost of a 6-minute rowing ergometer exercise was calculated at 36 kcal/min, one of the highest energy costs so far reported for any predominantly aerobic-type sport. Aerobic and anaerobic calculations show that 70 to 75% of the energy necessary to row the standard 2000m distance for men is derived from aerobiosis while the remaining 25 to 30% is anaerobic. Women achieve V̇O2max values of 4.1 ± 0.4 L/min and slightly lower anaerobic values than men. The relative 60 to 65% energy contribution of aerobic metabolism and 35 to 40% for anaerobiosis is not surprising since women compete at 1000m.Rowers also exhibit excellent isokinetic leg strength and power when compared with other elite athletes and oarswomen produced higher relative leg strength values than men when lean body mass is considered. Muscle fibre type distributions in oarsmen resemble those of distance runners while women tend to have a slightly higher proportion of fast-twitch fibres. An average power output of 390 ± 13.6W was produced by oarsmen for 6 minutes of simulated rowing while women were able to develop 300 ± 18.4 for 3 minutes of the same activity. Mechanical efficiency for rowing was calculated at 20 ± 0.9%. Oarsmen also achieve very high ventilation volumes being able to average above 200 L/min BTPS for 6 minutes of simulated rowing; women ventilate 170 L/min BTPS for 3 minutes of this exercise. Excellent V̇O2max and O2 pulse values demonstrate outstanding cardiorespiratory efficiency. Both oarsmen and oarswomen utilise a unique physiological pattern of race pacing; they begin exertion with a vigorous sprint which places excessive demands on anaerobic metabolism followed by a severely high aerobic steady-state and then an exhaustive sprint at the finish. Tolerance to excessive anaerobiosis is evident by very high lactates and O2 deficits measured during the first 2 minutes of exercise. Physiological profiles of successful international calibre rowing athletes have been established as a result of studies described in this review and the data have been used in a variety of ways to improve rowing performance.

Creatine supplementation improves muscular performance in older men.

PURPOSE Creatine supplementation has been shown to enhance muscle strength and power after only 5-7 d in young adults. Creatine supplementation could therefore benefit older individuals because aging is associated with a decrease in muscle strength and explosive power. METHODS We examined the effects of 7 d of creatine supplementation in normally active older men (59-72 yr) by using a double-blind, placebo-controlled design with repeated measures. After a 3-wk familiarization period to minimize learning effects, a battery of tests was completed on three occasions separated by 7 d (T1, T2, and T3). After T1, subjects were matched and randomly assigned into creatine (N = 10) and placebo (N = 8) groups. After T2, subjects consumed supplements (0.3 g x kg(-1) x d(-1)) for 7 d until T3. All subjects were tested for maximal dynamic strength (one-repetition maximum leg press and bench press), maximal isometric strength (knee extension/flexion), upper- and lower-body explosive power (6 x 10-s sprints on a cycle ergometer), and lower-extremity functional ability (timed sit-stand test and tandem gait test). Body composition was assessed via hydrostatic weighing, and blood samples were obtained to assess renal and hepatic responses and muscle creatine concentrations. RESULTS No significant increases in any performance measures were observed from T1 to T2 with the exception of isometric right-knee flexion in the placebo group indicating stability in the testing protocols. Significant group-by -time interactions indicated the responses from T2 to T3 were significantly greater (P <or= 0.05) in the creatine compared with the placebo group, respectively, for body mass (1.86 and -1.01 kg), fat-free mass (2.22 and 0.00 kg), maximal dynamic strength (7-8 and 1-2%), maximal isometric strength (9-15 and -6 to 1%), lower-body mean power (11 and 0%), and lower-extremity functional capacity (6-9 and 1-2%). No adverse side effects were observed. CONCLUSION These data indicate that 7 d of creatine supplementation is effective at increasing several indices of muscle performance, including functional tests in older men without adverse side effects. Creatine supplementation may be a useful therapeutic strategy for older adults to attenuate loss in muscle strength and performance of functional living tasks.

Human muscle fiber types in power lifters, distance runners and untrained subjects.

SummaryMuscle biopsies were taken from the vastus lateralis of 12 males: 5 control subjects, 4 power lifters and 3 distance runners. Three fiber “types” were distinguished by comparing serial sections for alkaline myofibrillar adenosine triphosphatase (ATPase) and succinic dehydrogenase (SDH) activities: 1. high ATPase and low SDH; fast-twitch-glycolytic (FG). 2. High ATPase and high SDH; fast-twitch-oxidative-glycolytic (FOG). 3. Low ATPase and high SDH; slow-twitch-oxidative (SO). In some cases the distinction between the FOG and FG classes was not clear and a group termed “transitional” was employed. A variation in percentage of fiber types and fiber area was found among individuals. The percentage of SO fibers varied from 19.6–60.1% within all 3 groups, with a mean of 40.5%. In the control group approximately 75% of the fibers were oxidative (FOG+SO). The major characteristics of the lifters were a decrease in the percentage of FOG fibers and a hypertrophy of FOG and FG fibers. The distance runners had a high percentage of oxidative fibers with few FG fibers. It is suggested that the fast-twitch fibers are mainly involved in the adaptation of muscle to exercise since the percentage of SO fibers varies greatly among individuals within and between the 3 groups studied.

Human skeletal muscle fiber type adaptability to various workloads.

Muscle biopsy specimens were removed from the vastus lateralis muscles of three groups of human subjects: controls, weight lifters, and distance runners. The runners proved to be a unique group with respect to the variables measured (low body weight and percentage body fat, and high VO2 max). Additionally, a histochemical analysis of the biopsy specimens revealed that the runners had a significantly higher percentage of fiber types I and IIC than either the controls or the weight lifters. Using a cryostatic retrieval method, each of the fibers identified histochemically was then analyzed morphometrically using electron microscopy. The results of volume-percent mitochondria demonstrated a strong relationship between the ATPase activity and oxidative potential of the fiber types for all three groups such that the oxidative activity would be ranked I greater than IIA greater than IIB. Irrespective of fiber type, there were significant differences between the groups with regard to muscle-fiber mitochondrial (runners greater than lifters greater than controls) and lipid content (runners greater than controls greater than lifters). The lifters had a significantly greater content of mitochondria than the controls, which may suggest that inactivity rather than the lifting exercise contributes to a low volume-percent mitochondria and a high percentage of type IIB fibers.

Reevaluation of Human Muscle Fast-Twitch Subtypes: Evidence for a Continuum

SummaryMuscle biopsies were removed from the vastus lateralis muscle of four healthy individuals with a unique fiber type distribution. Fibers were divided into slow-twitch (type I) and fast-twitch (types IIA, IIAB, and IIB) based upon the pH lability of myofibrillar ATPase. An unusually high percentage of types IIB and IIAB allowed a quantitative ultrastructural characterization of the subtype populations, especially with regard to type IIAB fibers. Using a cryostat retrieval method, histochemically-identified fibers were investigated by stereological electron microscopy. The volume percent mitochondria was significantly different for all fiber types. Likewise, lipid volume percent was significantly different between type I and type II fibers and between the fast-twitch subtypes IIA and IIB. However, these ultrastructural data revealed considerable overlap between the fiber types for metabolic parameters, as has been described through quantitative histochemistry by others. The fiber type which stained intermediately between types IIA and IIB at a preincubation pH of 4.6 (type IIAB) was also found to be intermediate in its oxidative components. These data suggest a continuum of fast-twitch fiber types which may tranform in response to the amount and type of usage.

Lipid depletion and repletion in skeletal muscle following a marathon.

Intramuscular lipid content was investigated in muscle biopsies from 10 well-trained endurance athletes before, immediately after, and 1, 3, 5, and 7 days after a marathon. Diets were controlled throughout the entire period of the study. Triglyceride content was ultrastructurally determined by the use of stereological methods. The volume percent lipid significantly decreased after the marathon and was lowest at 3 days post-marathon, rising slightly but still 35% lower than the pre-marathon value by 7 days post-marathon. Glycogen granules were abundant and tightly packed in the pre-marathon biopsies, scarce immediately post-marathon, and abundant, but less tightly packed, 7 days post-marathon. Post-marathon fluctuations in the volume percentages of mitochondria indicated possible fluid shifts within the muscle fibers: dehydration immediately post-marathon followed by rehydration with possible edema. Assuming the content of mitochondria remained constant throughout the recovery period, the ratio of the volume percentage of lipid to the volume percentage of mitochondria indicated that lipid content may have reached pre-marathon levels after 7 days post-marathon.