Gender affects response to weight training, but race doesn’t

Black athletes are disproportionately represented in power sports such as basketball, baseball, football and sprinting. Conventional wisdom suggests that black people respond better to strength and power training than white people. Likewise, men are stronger than women, so it’s logical that a gender difference exists in response to weight training. 10-week University of Maryland strength –training study of nearly 200 white and black men and women (average age 63) found no racial differences in strength faster than women. The people did knee extensions with one leg and rested the other leg. Strength training caused a 10 percent increase in muscle mass in the exercised leg, but no change in the unexercised leg. Also, training had no effect on the amount of fat covering the leg or on intramuscular fat. Men gained only about 2 percent more muscle mass from training than women. This study showed that older blacks and whites made similar gains during a weight-training program, and men made slightly greater gains than women. These results might not apply to younger trained athletes. (Medicine Science Sports Exercise, 40: 669-676, 2008)

High-speed eccentric contractions cause more muscle damage

Muscles contract eccentrically when they exert force as they lengthen, and contract concentrically when they exert force as they shorten. During concentric contractions, force decreases as velocity increases. The opposite happens during eccentric contractions: force increases as velocity increases. The high force created during eccentric contractions causes muscle damage that results in delayed-onset muscle soreness. Australian researchers found that muscle damage was greater following high-speed eccentric training than slow-speed eccentric training. Damage was most evident following high volume training. Kettlebell training involves high-speed eccentric contractions. It is extremely popular with bodybuilders, power athletes and general fitness enthusiasts. However, kettlebell exercises such as swings involve a pendulum motion with no firm endpoint. The results of this study probably do not apply to kettlebell training. (Medicine Science Sports Exercise, 40: 926-933, 2008)

Tourniquet training is the latest “breakthrough” coming from the research lab. The technique involves doing low-intensity exercises with muscle blood flow cutoff. Cutting off blood flow may trigger cell damage, inflammation, and increase stress and anabolic hormone release. Japanese researchers found that athletes doing knee extensions with a tourniquet wrapped around their thigh increased muscle size and strength more than athletes doing low-intensity knee extensions without a tourniquet. Researchers from the University of Texas Medical Branch in Galveston found that restricting blood flow during weight training was no more effective for stimulating protein synthesis than weight-training alone. They studied the effects of high-repetition, low-intensity knee extensions (75 repetitions at 20 percent of 1-rep maximum weight) with and without blood flow restriction on gene activity associated with protein synthesis. The study is important because it shows that low-intensity weight training can influence muscle protein synthesis and trigger muscle hypertrophy in some fibers. While this type of training is not effective for serious bodybuilders or young power athletes, it might be applicable in older adults who might be incapable of handling heavy loads. (Medicine Science Sports Exercise, 40: 691-698, 2008)

Scientists finally understand how muscles increase in size and strength. The process was summarized in an article by researchers from the University of Connecticut, Storrs. Genes, age and gender limit the capacity for muscle growth, but program structure, nutrition and fitness are modifiable factors that influence the rate of muscle hypertrophy and the ultimate size and strength of muscles. The structure of the weight-training program influences hormone release, immune system responses, recruitment of motor units (muscle fibers and their nerves) and blood flow. These activate signaling pathways in the cells that turn on genes regulating muscle trophy. This leads to muscle strength, power and endurance. Translating this complicated process is as much art as science. The appropriate training stress varies with the individual. For example, a training program that triggers muscle damage and inflammation can cause increased muscle strength and size in one person, but cause injury in another. Program structure is another issue. High-intensity, low-volume sets recruit mainly fast-twitch motor units, while low-intensity, high-volume training recruits smaller, slower and weaker motor units. You only train motor units if you use them, so the structure of the program must reflect your goals. This is a must-read paper for all serious bodybuilders and power athletes. (Sports Medicine, 38: 527-540, 2008)

Muscles grow in response to physical or chemical stress, so it seems reasonable that restricting blood flow to muscles during training would promote hypertrophy. Occlusion training involves performing exercises with restricted blood flow to the working muscles. Cutting off blood flow may trigger cell damage, inflammation and increase stress and anabolic hormone release. Japanese researchers found that athletes doing knee extensions with a tourniquet wrapped around their thigh increased muscle size and strength more than athletes doing low-intensity knee extensions without a tourniquet. A study by Brazilian and American scientists found that restricting blood flow during an eight-week training program was no more effective for increasing muscle size or strength then weight-training alone. They studied the effects of high-intensity (6 repetition maximum) and medium-intensity (12 repetitions maximum) knee extensions training with and without blood flow restriction. High and medium intensity strength training with restricting muscle blood flow was no more effective than nonrestricted blood flow training. (International Journal Sports Medicine, 29: 664-6 667, 2008)

Muscles contract eccentrically when they exert force as they lengthen and concentrically when they shorten. Most weight training exercises involve combinations of concentric (shortening), eccentric (lengthening) and static (isometric) muscle contractions. Many leading muscle physiologists think that eccentric training might be superior to traditional weight training. Eccentric contractions are less metabolically demanding than concentric contractions and can create more force. On the flipside, eccentrics cause more muscle damage and post-exercise muscle soreness. A University of Florida study found that five weeks of eccentric-enhanced training was no more effective than traditional weight training for increasing strength (bench press and squat), total testosterone, free testosterone and growth hormone. Eccentric-enhanced training involved 3 sets of 6 repetitions in the bench press and squat at 40 percent one-repetition maximum (1 RM) during the concentric part of the lift and 100 1 RM during the eccentric part pf the lift. Traditional training involved 4 sets of reps in the bench press and squat at 52.5 percent of 1 RM. This was a small, short-term study, so we need more research to help us understand the benefits and limitations of eccentric training. (Journal of Strength and Conditioning Research, 22: 1205-1214, 2008)

Physical performance and anabolic hormone levels vary during the day, a phenomenon called diurnal variation. Strength, power and endurance are greater in the afternoon than in the morning. Does this mean that afternoon training is best? People who exercise in the morning reduce the normal diurnal variations in physical performance. A Finnish study showed that normal hormone variations largely disappeared when people trained in the morning versus the afternoon. Subjects trained between 5 and 9 p.m. for 10 weeks and were divided into two groups that trained either in the morning or early evening. Training time had no effect on strength gains. Morning training reduced the normal strength variation between morning and afternoon. Testosterone and cortisol levels were highest in the morning and decreased during the day. This trend was not affected by training. The study showed that athletes might benefit from training at the same time of the day they must compete. This has implications for athletes competing in different time zones. (Chronobiology International, 24: 1159-1177, 2007)

Intense training is essential for maximum gains in bodybuilding and power sports. The body has a limited capacity to recover from maximal exercise, so athletes are always on the lookout for effective restorative techniques. Popular methods include contrast baths (alternately soaking in hot and cold water during recovery) and compression clothing consisting of elastic materials such as Lycra that squeeze and compress the large muscles of the body. British researchers found that neither technique enhanced recovery from exercise that causes muscle damage and soreness. Young men completed a “resistance exercise challenge” consisting of squats (6 sets of 10 repetitions), with a 5-second eccentric squat between sets. The workout was designed to trigger muscle damage and post-exercise soreness. After exercise, subjects received a contrast bath treatment, wore compression clothing, or did nothing (control). There were no differences between groups at 1 hour, 24 hours, or 48 hours of recovery in markers of muscle damage (creatine kinase, myoglobin), the perception of soreness, or physical performance. Contrast baths and compression clothing are no better than rest for promoting recovery from muscle-damaging exercise. (Medicine Science Sports Exercise, 40: 1297-1306, 2008)

Overtraining is an imbalance between training and recovery. Athletes and coaches need accurate measures of recovery to help them develop optimal training programs. These measures can be simple (e.g., morning heart rate, perception of energy level, feeling of well-being) or complex (e.g., testosterone-cortisol ratio, creatine kinase, growth hormone, glutamine). Spanish researchers proposed that urinary anabolic and catabolic steroids might be a good measure of recovery. Recreationally fit young men did 3 sets of 10 repetitions of 6 exercises at 75 percent of maximum effort with3 minutes rest between sets. Urine androgen levels (testosterone, epitestosterone, androstenedione, androstosterone, dehydroepiandrosterone, etiocholanolone) decreased after exercise and at 3 hours of recovery, but rebounded to baseline or above 48 hours after the workout. Urinary corticosteroid levels were unchanged before and after exercise. Urinary androgen levels might be an accurate, but impractical way to measure recovery from weight training. (Journal Strength Conditioning Research, 22: 1087-1 1093, 2008)

Growth hormone (GH) helps regulate the metabolism of fats, proteins and carbohydrates. During exercise, GH levels increase in proportion to exercise intensity and active muscle mass. British scientists showed that GH levels were higher during endurance cycling than sprinting or resistance exercise. They compared the growth hormone response to weight training (30 minutes, sprinting (30-second sprint on a stationary bicycle) and endurance cycling (2 hours at 70 percent of maximum effort) in young (18-25 years) and middle-aged men (40-50 years). Growth hormone levels after exercise followed the same trends in both age groups, but the levels were higher in the younger men. It’s unclear whether these differences were due to aging or higher exercise intensities in the younger group. It would have been interesting to compare growth hormone responses in young and old men with the same exercise capacity and power output. (Applied Physiology Nutrition Metabolism, 33: 706-7 712, 2008)