Marko T. Korhonen

Biomechanical and Skeletal Muscle Determinants of Maximum Running Speed with Aging

PURPOSE Aging diminishes the ability to run fast, but the specific mechanisms responsible for this deterioration remain largely unknown. In the present study, we investigated the age-related decline in sprint running ability through a cross-sectional examination of biomechanical and skeletal muscle characteristics in 77 competitive male sprinters aged 17-82 yr. METHODS Ground reaction force (GRF) and kinematic stride cycle parameters were measured during the maximum-velocity phase using a 9.4-m-long force platform. Knee extensor (KE) and ankle plantar flexor (PF) structural characteristics were investigated using ultrasonography and muscle biopsies (vastus lateralis). Force production characteristics of leg extensor muscles were determined by dynamic and isometric contractions. RESULTS The main findings were as follows: 1) the progressive age-related decline in maximum running velocity (Vmax) was mainly related to a reduction in stride length (Lstr) and an increase in ground contact time (tc), whereas stride frequency showed a minor decline and swing time remained unaffected; 2) the magnitude of average braking and push-off resultant GRFs declined with age and associated with Lstr, tc, and Vmax; 3) there was an age-related decline in muscle thickness, Type II fiber area and maximal and rapid force-generating capacity of the lower limb muscles; and 4) muscle thickness (KE + PF) was a significant predictor of braking GRF, whereas the countermovement jump height explained most of the variance in push-off GRF in stepwise regression analysis. CONCLUSIONS Age-related slowing of maximum running speed was characterized by a decline in stride length and an increase in contact time along with a lower magnitude of GRFs. The sprint-trained athletes demonstrated an age-related selective muscular atrophy and reduced force capacity that contributed to the deterioration in sprint running ability with age.

Age-related Differences in 100-m Sprint Performance in Male and Female Master Runners

PURPOSE This study was undertaken to investigate age-related differences in the velocity and selected stride parameters in male and female master sprinters and to determine which stride characteristics were related to the overall decline in the performance of the 100 m with age. METHODS The performances of 70 finalists (males 40-88 yr, females 35-87 yr) at the European Veterans Athletics Championships were recorded using two high-speed cameras (200 Hz) with a panning video technique and distance markers at 10-m intervals. Velocity, stride length (SL), stride rate (SR), ground contact time (CT), and flight time (FT) during the acceleration, peak velocity, and deceleration phases of the 100-m race were determined from the video records with the aid of the Peak Performance analysis system. RESULTS There was a general decline in sprint performances with age, the decrease becoming more evident around 65-70 yr of age. The velocity during the different phases of the run declined on average from 5 to 6% per decade in males and from 5 to 7% per decade in females. Similarly, SL showed clear reductions with increasing age, whereas SR remained unchanged until the oldest age groups in both genders. Furthermore, the CT, which correlated with velocity, was significantly longer, and FT, which correlated with both velocity and SL, was shorter in older age groups. CONCLUSION Our findings indicated that age-associated differences in velocity in elite master sprinters were similar in each phase of the 100-m run. The deterioration of the overall performance with age was primarily related to reduction in SL and increase in CT.

Effects of combined strength and sprint training on regulation of muscle contraction at the whole‐muscle and single‐fibre levels in elite master sprinters

Aim:  This study aims at examining the effects of progressive strength and sprint training on regulation of muscle contraction at the whole‐muscle and single‐fibre levels in older sprint‐trained athletes.

Which muscles compromise human locomotor performance with age

Ageing leads to a progressive decline in human locomotor performance. However, it is not known whether this decline results from reduced joint moment and power generation of all lower limb muscle groups or just some of them. To further our understanding of age-related locomotor decline, we compare the amounts of joint moments and powers generated by lower limb muscles during walking (self-selected), running (4 m s−1) and sprinting (maximal speed) among young, middle-aged and old adults. We find that age-related deficit in ankle plantarflexor moment and power generation becomes more severe as locomotion change from walking to running to sprinting. As a result, old adults generate more power at the knee and hip extensors than their younger counterparts when walking and running at the same speed. During maximal sprinting, young adults with faster top speeds demonstrate greater moments and powers from the ankle and hip joints, but interestingly, not from the knee joint when compared with the middle-aged and old adults. These findings indicate that propulsive deficit of ankle contributes most to the age-related locomotor decline. In addition, reduced muscular output from the hip rather than from knee limits the sprinting performance in older age.

Bone Density, Structure and Strength, and Their Determinants in Aging Sprint Athletes.

PURPOSE This study was undertaken to examine bone properties in masters sprinters of different ages and younger reference subjects. In addition, the association of sport-specific ground reaction force, muscle, training, and hormone characteristics with the bone parameters was evaluated in the athletes. METHODS Bone densitometric, structural, and strength parameters were assessed by peripheral quantitative computed tomography at the distal and midtibia in 83 male sprinters (40-85 yr) and 19 physically active referents (31-45 yr). Between-group differences were analyzed by ANCOVA with body mass and height as covariates. RESULTS Bone values were generally greater in athletes than referents, the greatest differences being in bending strength of the tibia shaft as estimated by maximum moment of inertia (Imax). Among athletes, trabecular volumetric bone mineral density of distal tibia was 12% (P < 0.05) lower in the oldest (≥70 yr) versus youngest group, whereas the total bone mineral content, total cross-sectional area, and compressive bone strength index did not differ between the groups. At midtibia, no age group differences were present in the total bone mineral content, total cross-sectional area, cortical wall thickness, cortical volumetric bone mineral density, polar mass distribution, minimum moment of inertia, or maximum moment of inertia. After controlling for age, body mass, and height, most loading-related characteristics, knee extensor muscle thickness, and hormone concentrations correlated with the bone parameters. Multivariate regression models explained 12%-67% (mean, 47.5%) of the variance of the bone parameters. Mechanical power in the eccentric phase of the hopping and body mass were consistently the strongest independent predictors in the models. CONCLUSION The results suggest that regular sprint training has positive (direction-specific) effects on bone strength and structure in middle- and older-aged athletes. Interindividual differences in bone traits seem to be due to combined effects of exercise loading, body size, and hormonal characteristics.

Triceps surae muscle-tendon properties in older endurance- and sprint-trained athletes

Previous studies have shown that aging is associated with alterations in muscle architecture and tendon properties (Morse CI, Thom JM, Birch KM, Narici MV. Acta Physiol Scand 183: 291-298, 2005; Narici MV, Maganaris CN, Reeves ND, Capodaglio P. J Appl Physiol 95: 2229-2234, 2003; Stenroth L, Peltonen J, Cronin NJ, Sipila S, Finni T. J Appl Physiol 113: 1537-1544, 2012). However, the possible influence of different types of regular exercise loading on muscle architecture and tendon properties in older adults is poorly understood. To address this, triceps surae muscle-tendon properties were examined in older male endurance (OE, n = 10, age = 74.0 ± 2.8 yr) and sprint runners (OS, n = 10, age = 74.4 ± 2.8 yr), with an average of 42 yr of regular training experience, and compared with age-matched [older control (OC), n = 33, age = 74.8 ± 3.6 yr] and young untrained controls (YC, n = 18, age = 23.7 ± 2.0 yr). Compared with YC, Achilles tendon cross-sectional area (CSA) was 22% (P = 0.022), 45% (P = 0.001), and 71% (P < 0.001) larger in OC, OE, and OS, respectively. Among older groups, OS had significantly larger tendon CSA compared with OC (P = 0.033). No significant between-group differences were observed in Achilles tendon stiffness. In older groups, Youngs modulus was 31-44%, and maximal tendon stress 44-55% lower, than in YC (P ≤ 0.001). OE showed shorter soleus fascicle length than both OC (P < 0.05) and YC (P < 0.05). These data suggest that long-term running does not counteract the previously reported age-related increase in tendon CSA, but, instead, may have an additive effect. The greatest Achilles tendon CSA was observed in OS followed by OE and OC, suggesting that adaptation to running exercise is loading intensity dependent. Achilles tendon stiffness was maintained in older groups, even though all older groups displayed larger tendon CSA and lower tendon Youngs modulus. Shorter soleus muscle fascicles in OE runners may be an adaptation to life-long endurance running.

Relation between muscle mass, motor units and type of training in master athletes

The aim of this study was to measure the number of motor units and muscle mass in power‐trained and endurance‐trained master athletes compared with community‐dwelling older adults.

Diffusion Capacity of the Lung in Young and Old Endurance Athletes

Lung diffusion capacity (D LCO) declines with age. A significant proportion of older endurance athletes develop exercise-induced hypoxemia (SaO2<95%). We hypothesised that master endurance athletes have a lower D LCO than age-matched non-athletes. We recruited 33 control (16 young; 17 old) and 29 male endurance athletes (13 young; 16 old) during the World Masters Athletics Indoor Championships, 2012 (Jyväskylä, Finland). To measure D LCO the participant exhaled to residual volume and then quickly inhaled to ≥ 90% total lung capacity from a gas source with 0.3% carbon monoxide. The D LCO and transfer coefficient (K CO) were corrected for the actual haemoglobin concentration. Spirometric function was similar in athletes and age-matched controls. D LCO and K CO were 33% and 25% lower in old and young controls, respectively (P<0.001). Although predicted D LCO and K CO were 11%-points higher in athletes than age-matched controls (P<0.001), they were 23% and 16% lower in old athletes than young controls, respectively (P<0.001). D LCO did not correlate with age-graded performance or weekly training hours. The better lung diffusion capacity in male endurance athletes than age-matched controls might be an adaptation to training, self-selection and/or attrition bias. However, the diffusion capacity of the older athlete is lower than that of the young non-athlete.

Walking and Running Require Greater Effort from the Ankle than the Knee Extensor Muscles.

INTRODUCTION The knee and ankle extensors as human primary antigravity muscle groups are of utmost importance in a wide range of locomotor activities. Yet, we know surprisingly little about how these muscle groups work, and specifically, how close to their maximal capacities they function across different modes and intensity of locomotion. Therefore, to advance our understanding of locomotor constraints, we determined and compared relative operating efforts of the knee and ankle extensors during walking, running, and sprinting. METHODS Using an inverse dynamics biomechanical analysis, the muscle forces of the knee and ankle extensors during walking (1.6 m·s), running (4.1 m·s), and sprinting (9.3 m·s) were quantified and then related to maximum forces of the same muscle groups obtained from a reference hopping test that permitted natural elastic limb behavior. RESULTS During walking, the relative effort of the ankle extensors was almost two times greater compared with the knee extensors (35% ± 6% vs 19% ± 5%, P < 0.001). Changing walking to running decreased the difference in the relative effort between the extensor muscle groups, but still, the ankle extensors operated at a 25% greater level than the knee extensors (84% ± 12% vs 63% ± 17%, P < 0.05). At top speed sprinting, the ankle extensors reached their maximum operating level, whereas the knee extensors still worked well below their limits, showing a 25% lower relative effort compared with the ankle extensors (96% ± 11% vs 72% ± 19%, P < 0.01). CONCLUSIONS Regardless of the mode of locomotion, humans operate at a much greater relative effort at the ankle than knee extensor muscles. As a consequence, the great demand on ankle extensors may be a key biomechanical factor limiting our locomotor ability and influencing the way we locomote and adapt to accommodate compromised neuromuscular system function.

What Makes a 97-Year-Old Man Cycle 5,000 km a Year?

Background: The nature versus nurture debate is one of the oldest issues in the study of longevity, health and successful aging. Objective: We present a 97-year-old man (I.K.) as an example of the effects of habitual exercise on the aging process. Methods: Extensive assessments included medical examinations, interviews, musculoskeletal structure, performance characteristics, cognitive function and gut microbiota composition. Results: I.K. suffers from iatrogenic hypogonadism, prostate cancer, hypothyroidism and a history of deep popliteal thrombosis. Notwithstanding, he cycles up to 5,000 km a year and participates in competitive sports. His musculoskeletal properties, athletic performance, cognitive function and gut microbiota are outstanding. Some traits even exceed those seen in middle-aged men. Conclusions: His long-term physically and intellectually active lifestyles combined with extensive social interactions have most likely contributed to his exercise capacity, despite his medical history.